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GRB 221009A

GCN Circular 32635

Subject
GRB 221009A: Swift detected transient may be GRB
Date
2022-10-09T20:44:25Z (3 years ago)
From
Jamie Kennea at Penn State U <jak51@psu.edu>
J. A. Kennea and M. Williams (PSU) report on behalf of the Swift Team:

We provide an update on the BAT trigger 1126853, AKA Swift J1913.1+1946   
(GCN #32632). Examination of XRT data from this trigger shows strong 
fading. We also note that Fermi/LAT has triggered on the same location.   
There is also a possible association with a Fermi/GBM trigger @ 
13:16:59UT. Given this, we believe that this source is now likely a 
Gamma-Ray Burst and not a Galactic Transient. If the GBM trigger is the   
same source, this would suggest a highly energetic outburst, and therefore
we strongly encourage follow-up of this usual event.

GCN Circular 32636

Subject
GRB 221009A: Fermi GBM detection of an extraordinarily bright GRB
Date
2022-10-09T20:54:36Z (3 years ago)
From
Peter Veres at UAH <veresp@gmail.com>
P. Veres (UAH),  E. Burns (LSU), E. Bissaldi (Politecnico and INFN
Bari), S. Lesage (UAH), O. Roberts (USRA)
report on behalf of the Fermi GBM Team:

"At 2022-10-09 13:16:59.000 UT on 9 October 2022, the Fermi Gamma-Ray
Burst Monitor (GBM) triggered and located GRB 221009A (trigger
687014224 / 221009553).

This event, if it is a GRB, it is the brightest among the GBM detected
GRBs. If it is not a GRB then it is a rare transient event. Follow-up
across all wavelengths is encouraged.

The on-ground calculated location, using the GBM trigger
data, is RA = 290.4, DEC = 22.3 (J2000 degrees,
equivalent to 19 h 22 m, 22 d 15 '), with a statistical uncertainty
of 1 degrees (radius, 1-sigma containment,
statistical only; there is additionally a systematic
error which we have characterized as a core-plus-tail model, with 90% of
GRBs having a 3.7 deg error and a small tail suffering a larger than 10 deg
systematic error. [Connaughton et al. 2015, ApJS, 216, 32] ).

This location is consistent with the Swift J1913.1+1946 localization
(Dichiara et al. GCN 32632)  though it precedes the Swift trigger by
an hour.


The angle from the Fermi LAT boresight at the GBM trigger time is 76 degrees.

The GBM light curve consists of an initial ~10 s long pulse, followed
by an extraordinarily bright episode at ~180 s after the trigger time,
lasting at least 100 seconds.



The analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog:
https://heasarc.gsfc.nasa.gov/W3Browse/fermi/fermigbrst.html

For Fermi GBM data and info, please visit the official Fermi GBM Support Page:
https://fermi.gsfc.nasa.gov/ssc/data/access/gbm/"

GCN Circular 32637

Subject
GRB 221009A or Swift J1913.1+1946: Fermi-LAT detection
Date
2022-10-09T21:45:05Z (3 years ago)
From
Elisabetta Bissaldi at INFN,Bari <elisabetta.bissaldi@ba.infn.it>
E Bissaldi (Politecnico and INFN Bari), N. Omodei (Stanford Univ.),
M. Kerr (NRL), report on behalf of the Fermi-LAT team:


At 14:17:05.99 on October, 09, 2022 Fermi-LAT detected high-energy emission
from Swift J1913.1+1946 or GRB 221009A, which was reported by
Swift (Dichiara et al. GCN #32632) and by GBM (Veres et al. GCN #32636).
The best LAT on-ground location is found to be

RA, Dec = 288.21, 19.73 (J2000)

with an error radius of 0.09 deg (90 % containment, statistical error only).
This was 94 deg from the LAT boresight at the time of the trigger.

The data from the Fermi-LAT show a significant increase in the event rate
that is spatially and temporally correlated with the trigger with high significance.

The 100 MeV - 1 GeV photon flux in the time interval 500-3500 s after
the Swift trigger is (1.27 +/- 0.16)E-05 ph/cm2/s.
The estimated photon index above 100 MeV is -2.12 +/- 0.11.
The highest-energy photon is a 7.8 GeV
which is observed 766 seconds after the Swift trigger.

The Fermi-LAT point of contact for this burst is
Elisabetta Bissaldi (elisabetta.bissaldi@ba.infn.it).


The Fermi-LAT is a pair conversion telescope designed to
cover the energy band from 20 MeV to greater than 300 GeV.
It is the product of an international collaboration
between NASA and DOE in the U.S. and many scientific
institutions across France, Italy, Japan and Sweden.

GCN Circular 32641

Subject
IPN triangulation of extremely bright GRB 221009A
Date
2022-10-10T01:10:40Z (3 years ago)
From
Dmitry Svinkin at Ioffe Institute <svinkin@mail.ioffe.ru>
D. Svinkin, D. Frederiks, A. Ridnaia, A. Lysenko,
and T. Cline on behalf of the Konus-Wind team,

A. Goldstein, M. S. Briggs, C. Wilson-Hodge,
and E. Burns on behalf of the Fermi GBM team,

E. Bozzo and C. Ferrigno, on behalf of the INTEGRAL SPI-ACS GRB team,

and

S. Barthelmy, J. Cummings, H. Krimm, D. Palmer, and A. Tohuvavohu
on behalf of the Swift-BAT team, report:

The extremely bright, long-duration GRB 221009A
(Swift-BAT detection of Swift J1913.1+1946:
Dichiara et al., GCN Circ. 32632; Kennea and Williams, GCN Circ. 32635;
Fermi-GBM detection: Veres et al., GCN Circ. 32636;
Fermi-LAT detection: Bissaldi et al., GCN Circ. 32636)
has been detected by Fermi (GBM trigger 687014224),
INTEGRAL (SPI-ACS), and Konus-Wind, so far,
at about 47820 s UT (13:17:00).

We have triangulated it to a Konus-GBN annulus centered at
RA(2000)=1.444 deg (00h 05m 47s) Dec(2000)=+3.590 deg (+3d 35' 25")
whose radius is 73.473 +/- 4.089 deg (3 sigma).

This localization may be improved.

The IPN localization is consistent with, but reduces the area of, the
Fermi-GBM one (glg_healpix_all_bn221009553_v01).

The IPN localization is consistent with Swift-BAT (GCN 32632) and
Fermi-LAT (GCN 32636) position of Swift J1913.1+1946, supporting that
Swift J1913.1+1946 is the afterglow of GRB 221009A.

A triangulation map is posted at
http://www.ioffe.ru/LEA/GRBs/GRB221009_T47819/IPN/

The Konus-Wind time history and spectrum will be given
in a forthcoming GCN Circular.

GCN Circular 32642

Subject
GRB 221009A: Fermi GBM observation
Date
2022-10-10T04:04:41Z (3 years ago)
From
Stephen Lesage at Fermi-GBM Team <sjl0014@uah.edu>
S. Lesage (UAH), P. Veres (UAH), O.J. Roberts (USRA),
E. Burns (LSU), and E. Bissaldi (Politecnico and INFN Bari)
report on behalf of the Fermi GBM Team:

"At 13:16:59.99 UT on 09 October 2022, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 221009A (trigger 687014224/221009553) which
was also detected by Swift-BAT (S. Dichiara, et al. 2022, GCN 32632;
J. A. Kennea, et al. 2022, GCN 32635), Fermi-LAT (E. Bissaldi et al. 2022,
GCN 32637), INTEGRAL (SPI-ACS), Konus-Wind, and triangulated by IPN
(D. Svinkin et al. 2022, GCN 32641). The GBM on-ground location (GCN 32636)
is
consistent with the Swift-BAT and Fermi-LAT locations and the IPN
localization.

The angle from the Fermi LAT boresight is 73 degrees.

The GBM light curve consists of two emission episodes, a single isolated
peak
followed by a longer, extremely bright, multi-pulsed emission episode with
a duration (T90) of about 327 s (10-1000 keV).

The time-averaged spectrum for the first emission episode
from T0-0.0 to T0+43.4 s is best fit by
a power law function with an exponential high-energy cutoff.
The power law index is -1.70 +/- 0.02 and the cutoff energy,
parameterized as Epeak, is 375 +/- 87 keV.
The event fluence (10-1000 keV) in this time interval is
(2.12 +/- 0.05)E-05 erg/cm^2.

Due to the brightness of the second emission episode, the likelihood of
pulse pile-up and other systematic effects are very high and no single
spectral model provides an adequate fit in this preliminary analysis.
The event fluence (10-1000 keV) from T0+175 to T0+1458 s
is on the order of (2.912 +/- 0.001)E-02 erg/cm^2.
The 1.024 sec peak photon flux measured
starting from T0+238.8 s in the 10-1000 keV band
is on the order of 2385 +/- 3 ph/s/cm^2,
making this the most intense and fluent GRB detected by Fermi GBM.

Further analysis is being performed.

The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog:
https://heasarc.gsfc.nasa.gov/W3Browse/fermi/fermigbrst.html

For Fermi GBM data and info, please visit the official Fermi GBM Support
Page:
https://fermi.gsfc.nasa.gov/ssc/data/access/gbm/"

GCN Circular 32644

Subject
GRB 221009A BOOTES-2/TELMA and OSN optical detections
Date
2022-10-10T07:40:13Z (3 years ago)
From
Youdong HU at IAA-CSIC <huyoudong072@hotmail.com>
Y.-D. Hu, V. Casanova, E. Fernandez-Garcia, M. A. Castro Tirado, M.D. Caballero-Garcia, I. Olivares, I. Perez-Garcia and R. Sanchez-Ramirez and A. J. Castro-Tirado (IAA-CSIC), C. Perez del Pulgar and A. Castellon (Univ. de Malaga), R. Fernandez-Munoz (IHSM/UMA-CSIC) and M. Jelinek (ASU-CAS), on behalf of a larger collaboration, report:

The 60cm BOOTES-2/TELMA robotic telescope at IHSM La Mayora (UMA-CSIC) in Algarrobo Costa (Malaga, Spain) responded to the extraordinarily bright GRB 221009A detected by Swift, Fermi, MAXI/GSC, INTEGRAL (SPI-ACS), Konus-Wind, and the IPN (Dichiara et al. GCNC 32632, Veres et al. GCNC 32636, Bissaldi et al. GCNC 32637, Svinkin et al. GCNC 32641, Negoro et al. ATEL 15651). A number of images (60s exposures in clear filter) were taken starting at 18:23 UT on 9 Oct (~ 4.2 hours after trigger). Due to passing clouds, the optical afterglow was only detected in frames around 18:44 UT with 16.21+/-0.11 mag.

Later on, we triggered the 0.9m telescope of the Observatiorio Sierra Nevada (OSN) near Granada, Spain. Observations started on 9 Oct 18:45 UT (~ 4.6 hours after trigger) in BVRI-bands (90 s exposures each). The optical afterglow is clearly detected with R=16.57+-0.02 mag on the first R-band image (gathered at 18:49 UT).

These detections are consistent with the ones reported by Lipunov et al. (GCNC 32634), Perley et al. (GCNC 32638) and Broens et al. (GCNC 32640). Further observations are ongoing.

We thank both the staff at La Mayora and OSN for their excellent support.

GCN Circular 32645

Subject
GRB 221009A (Swift J1913.1+1946): Mondy optical observations
Date
2022-10-10T08:10:47Z (3 years ago)
From
Alexei Pozanenko at IKI, Moscow <apozanen@iki.rssi.ru>
S. Belkin (IKI, HSE), A. Pozanenko (IKI), E. Klunko (ISTP), N. Pankov 
(HSE)  report  on behalf of GRB IKI FuN:

We observed GRB 221009A (Swift J1913.1+1946) (Swift-BAT detection of 
Swift J1913.1+1946: Dichiara et al., GCN 32632; Kennea and Williams, GCN 
  32635; Fermi-GBM detection: Veres et al., GCN  32636; Fermi-LAT 
detection: Bissaldi et al., GCN  32636, IPN localization: Svinkin et 
al., GCN 32641) with AZT-33IK telescope of Sayan observatory (Mondy) 
starting on 2022-10-09 (UT) 14:26:54 and continuing to 15:34:05.

We clearly detect the optical afterglow (Dichiara et al., GCN 32632; 
Lipunov et al., GCN 32634; Perley GCN 32638; Hu et al., GCN 32644). 
Preliminary photometry of the afterglow at the first image is following

Date       UT start   t-T0       Filter Exp.   OT    Err.  UL(3sigma)
                     (mid, days)        (s)

2022-10-09 14:26:54  0.01223     R      120    14.84 0.09  20.8

We observe a monotonic decay in brightness, which can be approximated by 
a power law with an index of -0.52.

The photometry is based on the nearby USNO-B1.0 stars (R2)

GCN Circular 32646

Subject
GRB 221009A (Swift J1913.1+1946): MeerLICHT observations
Date
2022-10-10T09:14:47Z (3 years ago)
From
Simon de Wet at UCT <dwtsim002@myuct.ac.za>
S. de Wet (UCT), P.J. Groot (Radboud/UCT/SAAO) report on behalf of the
MeerLICHT consortium:

Following the detection by Swift of a bright hard new X-ray and optical
transient (Dichiara et al., GCN 32632), the 0.6m wide-field MeerLICHT
telescope, located at Sutherland, South Africa, started automatic
observations of the BAT error box beginning at 17:49:44 UT on 2022 October
9. Observations consisted of 60s exposures in the q,u,g,r,i,z bands
following the sequence quqgqrqiqz and continued for approximately 1 hour.
Some of our observations were affected by cirrus clouds.

We detect a source at the Swift/UVOT position (Dichiara et al., GCN 32632)
consistent with other optical detections (Lipunov et al., GCN 32634; Perley
et al., GCN 32638; Broens, GCN 32640), and report the following 3-sigma
u-band upper limit and detections in the AB magnitude system:

u > 17.91 at 18:06:27 UT
g = 18.22 +/- 0.33 at 18:21:07 UT
q = 17.19 +/- 0.07 at 18:05:00 UT
r = 17.76 +/- 0.08 at 18:23:59 UT
i = 15.58 +/- 0.03 at 18:26:56 UT
z = 14.89 +/- 0.03 at 18:29:55 UT

MeerLICHT is built and run by a consortium consisting of Radboud
University, University of Cape Town, the South African Astronomical
Observatory, the University of Oxford, the University of Manchester and the
University of Amsterdam.

GCN Circular 32647

Subject
GRB 221009A: Nanshan/NEXT photometry and Xinglong-2.16m spectroscopy
Date
2022-10-10T09:19:26Z (3 years ago)
From
Dong Xu at NAOC/CAS <dxu@nao.cas.cn>
D. Xu, S.Q. Jiang, S.Y. Fu, X. Liu (NAOC), Z.P. Zhu (NAOC, HUST), T.H. 
Lu (NAOC), X. Gao (Urumqi No.1 Senior High School), J.Z. Liu (XAO) report:

We observed the field of the optical counterpart of Swift J1913.1+1946 
or GRB 221009A detected by Swift (Dichiara, GCN 32632), using the 
NEXT-0.6m telescope located at Nanshan, Xinjiang, China. Observations 
started at 14:25:55 UT on 2022-10-09, i.e., 762 s after the Swift/BAT 
trigger. A series of frames in the Sloan r- and z- filters were obtained.

The optical counterpart is clearly detected in each of our images, which 
decays from r ~ 14.93 to r ~ 16.50 within ~ four hours, with a decay 
index of \alpha ~ 0.5 (F_t ~ t^-\alpha), calibrated the nearby PS1 
stars. The decaying behavior is consistent with that for conventional 
GRBs.

Spectroscopy of the optical counterpart was performed at the 2.16m 
telescope equipped with the BFOSC camera at Xinglong, Hebei, China. The 
spectrum covers the wavelength range 3800-9000 AA. The observation mid 
time is 2022 Oct 10.63 UT, i.e., 0.95 hr after the BAT trigger.

The spectrum is dominated by a red continuum due to very high Galactic 
extinction, and no prominent absorption feature can be identified. Given 
the detections by Swift/UVOT as well as spectral continuum, the event 
could be real GRB 221009A at a rather low redshift.

We thank the great support of the Xinglong-2.16m staff, in particular 
Junjun Jia, Min He, Aiying Zhou, and Jie Zheng.

GCN Circular 32648

Subject
GRB 221009A: Redshift from X-shooter/VLT
Date
2022-10-10T09:39:41Z (3 years ago)
From
Antonio de Ugarte Postigo at OCA <deugarte@oca.eu>
A. de Ugarte Postigo (OCA), L. Izzo (DARK/NBI), G. Pugliese 
(Amsterdam Univ. and Leiden Observatory), D. Xu (NAOC), 
B. Schneider (CEA Paris-Saclay), J.P.U. Fynbo (DAWN/NBI), 
N.R. Tanvir (Univ. Leicester), D.B. Malesani (Radboud Univ. 
and DAWN/NBI), A. Saccardi (GEPI, Observatoire de Paris),  
D. A. Kann (Goethe Univ.), K. Wiersema (Lancaster Univ.), 
B. P. Gompertz (Birmingham), C. C. Thoene (ASU-CAS) and 
A. J. Levan (Radboud Univ.) report on behalf of the Stargate 
collaboration:

We observed the afterglow of the extremely bright GRB221009A 
(Dichiara et al., GCN 32632; Kennea & Williams, GCN 32635; 
Bissaldi et al., GCN 32637; Veres et al., GCN 32636; Lesage et 
al., GCN 32642) with X-shooter at ESO's UT3 of the Very Large 
Telescope (Paranal, Chile). The observations started at 
00:49:58.9 UT  (11.55 hr after the GBM trigger and 10.66 hr 
after the BAT trigger). The observation consisted of 4x600s with 
a spectral coverage between 3000 and 21000 AA.

We detect a very red continuum with absorption features that 
correspond to CaII, CaI and NaID at a redshift of z = 0.151. We 
also detect multiple features due to the Milky Way���s interstellar 
medium, due to the large Galactic column density of material 
along this line of sight. At this redshift the event has an isotropic 
equivalent energy of Eiso=2x10^54 erg (using the GBM fluence 
reported in GCN 32642), barring saturation effects in the 
Fermi/GBM fluence. This is within the upper end of GRB 
energetics. Further follow-up is strongly encouraged.

We acknowledge the excellent support provided by the Paranal 
staff, in particular A. Escorza and Zahed Wahhaj.

GCN Circular 32650

Subject
GRB 221009A (Swift J1913.1+1946): AGILE/MCAL detection
Date
2022-10-10T10:50:44Z (3 years ago)
From
Alessandro Ursi at INAF/IAPS <alessandro.ursi@gmail.com>
A. Ursi (INAF/IAPS), G. Panebianco (INAF/OAS-Bologna), C. Pittori, F.
Verrecchia (SSDC, and INAF/OAR), F. Longo (Univ. Trieste and INFN Trieste),
N. Parmiggiani (INAF/OAS-Bologna), M. Tavani (INAF/IAPS, and Univ. Roma Tor
Vergata), A. Argan, M. Cardillo, C. Casentini, Y. Evangelista, L. Foffano,
E. Menegoni, G. Piano (INAF/IAPS), F. Lucarelli (SSDC, and INAF/OAR), A.
Addis, L. Baroncelli, A. Bulgarelli, A. Di Piano, V. Fioretti, F. Fuschino
(INAF/OAS-Bologna), M. Romani (INAF/OA-Brera), M. Marisaldi
(INAF/OAS-Bologna, and Bergen University), M. Pilia, A. Trois
(INAF/OA-Cagliari), I. Donnarumma (ASI), A. Giuliani (INAF/IASF-Mi), and P.
Tempesta (TeleSpazio), report on behalf of the AGILE Team:

The AGILE satellite detected the bright emission classified as GRB 221009A
or Swift J1913.1+1946, reported by Swift BAT (GCN #32635) at T0 =
2022-10-09 13:16:59 (UTC), by Fermi GBM (GCNs # 32636, #31782), Fermi LAT
(GCN #32637), and IPN (GCN #32641).

The burst is clearly visible in the AGILE scientific ratemeters of the
MiniCALorimeter detector (MCAL; 0.4-100 MeV) and in all the five panels of
the AntiCoincidence system (AC Top, 50-200 keV; AC Lat, 80-200 keV). The
event consisted of several episodes, exhibiting an entire duration of about
600 s. The first episode lasted about 10 s and it released a total number
of 13870 counts in the MCAL detector (above a background rate of 1130 Hz),
and 31880 counts in the AC Top detector (above a background rate of 2980
Hz). The central episodes released a very large fluence, which produced
saturation effects in both MCAL and AC count rates, preventing a reliable
evaluation of the integrated counts. The last episode lasted 73 s and
released a total number of 517170 counts in the AC Top detector (above a
background rate of 2755 Hz). The AGILE ratemeter light curves can be found
at http://www.agilescienceapp.it/notices/GRB221009A_AGILE_RM.png .

The event also triggered two partial high time resolution MCAL data
acquisitions, covering the onset of the central episodes. The
time-integrated spectrum of the first trigger, from T0+181.00 s to
T0+194.03 s, can be fitted in the energy range 0.5-5 MeV with a power-law
with ph.ind. = -2.07 (-0.04,+0.04), resulting in a reduced chi-squared of
1.98 (32 d.o.f.) and a fluence of 5.88e-04 erg/cm^2 (90% confidence level),
in the same energy range. Due to the extremely high fluence, the second
trigger is affected by pile-up and count rate saturation, preventing a
reliable evaluation of the corresponding energy spectrum. The MCAL light
curve can be found at
http://www.agilescienceapp.it/notices/GRB221009A_080412_592406219.000000.png
.

At the T0, the event was 100 deg off-axis.

Additional analysis of AGILE data is in progress. Automatic MCAL GRB alert
Notices can be found at: https://gcn.gsfc.nasa.gov/agile_mcal.html.

GCN Circular 32651

Subject
GRB 221009A: Swift-XRT refined Analysis
Date
2022-10-10T11:19:36Z (3 years ago)
From
Phil Evans at U of Leicester <pae9@leicester.ac.uk>
J.A. Kennea (PSU), A. Tohuvavohu (U. Toronto), J.P. Osborne (U.
Leicester), K.L. Page (U. Leicester), A.P. Beardmore (U. Leicester), A.
Melandri (INAF-OAB), T. Sbarrato (INAF-OAB), P. D'Avanzo (INAF-OAB),
D.N. Burrows (PSU) and E Bissaldi report on behalf of the Swift-XRT
team:

We have analysed 12 ks of XRT data for GRB 221009A (E Bissaldi et al.
GCN Circ. 32637), from 159 s to 58.4 ks after the  BAT trigger. The
data are entirely in Windowed Timing (WT) mode (the first 10 s were
taken while Swift was slewing). A spectrum formed from the WT mode data
can be fitted with an absorbed power-law with a photon spectral index 
of 1.836 (+0.012, -0.011). The best-fitting absorption column is  6.76
(+/-0.16) x 10^21 cm^-2, at a redshift of 0.151, in addition to the
Galactic value of 5.4 x 10^21 cm^-2 (Willingale et al. 2013). The
counts to observed (unabsorbed) 0.3-10 keV flux conversion factor
deduced from this spectrum  is 5.7 x 10^-11 (1.0 x 10^-10) erg cm^-2
count^-1. 

A summary of the WT-mode spectrum is thus:
Galactic foreground: 5.4 x 10^21 cm^-2
Intrinsic column:    6.76 (+/-0.16) x 10^21 cm^-2 at z=0.151
Photon index:	     1.836 (+0.012, -0.011)

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/01126853.

This circular is an official product of the Swift-XRT team.

GCN Circular 32652

Subject
GRB 221009A: REM optical and NIR detection of the afterglow
Date
2022-10-10T11:22:17Z (3 years ago)
From
Paolo D'Avanzo at INAF-OAB <pda.davanzo@gmail.com>
R. Brivio, M. Ferro, P. D'Avanzo, D. Fugazza (INAF-OAB), A. Melandri (INAF-OAR), S. Covino (INAF-OAB) 
on behalf of the REM team, report:

We observed the field of GRB 221009A (Dichiara et al., GCN 32632; Kennea & Williams, GCN 32635; Veres et al., 
GCN 32636; Bissaldi et al., GCN 32637; Svinkin et al., GCN 32641; Ursi et al., GCN Circ. 32650) with the REM 
60cm robotic telescope  located at the ESO premise of La Silla (Chile). The observations were carried in the 
g, r, i, z, J, H and K bands, starting on 2022 Oct 09 at 23:43:02 UT (i.e. about 10.43 hours after the GBM trigger) 
and lasted for about 1 hour.

The optical and NIR afterglow is detected in all bands. From preliminary photometry, we derive the following magnitudes:

r = 17.36 +/- 0.12
(AB; calibrated against the the Pan-STARRS catalogue)

H = 12.21 +/- 0.04
(Vega; calibrated against the 2MASS catalogue) 


at a mid time of t-t0 ~ 10.47 hours after the GBM trigger.

GCN Circular 32653

Subject
GRB 221009A/Swift J1913.1+1946: AMI-LA observations
Date
2022-10-10T12:10:49Z (3 years ago)
From
Lauren Rhodes at Oxford <lauren.rhodes@physics.ox.ac.uk>
Joe Bright, Lauren Rhodes, Rob Fender (University of Oxford), Wael Farah, Alex Pollak, Andrew Siemion (SETI Institute) report:



We observed the field of the candidate gamma-ray burst GRB 221009A (Swift J1913.1+1946; ATel #15650, ATel #15651) with the Arcminute Microkelvin Imager Large-Array (AMI-LA) at 15.5 GHz beginning at UT 16:25:25.5 on 09-Oct-2022 (approximately 2 hours 15 minutes after the initial BAT trigger reported in ATel #15650) for a total of 4 hours. The flux standard 3c286 was used to calibrate the bandpass response and flux scale of the AMI-LA and J1925+2106 was used as an interleaved complex gain calibrator.

We detect a bright unresolved source at a position consistent with the one reported in ATel #15651 at a (preliminary) flux density of 39 +/- 2 mJy (including both a statistical uncertainty and a 5% absolute flux scale uncertainty). There is no significant emission at this position in either the VLA Sky Survey (VLASS; Lacy+2020) or the NRAO VLA Sky Survey (NVSS; Condon+1998), and so we identify this new source as the radio counterpart to GRB221009A/Swift J1913.1+1946. Further observations are planned.

We thank the staff at the Mullard Radio Astronomy Observatory for carrying out these observations and operating the AMI-LA.

GCN Circular 32654

Subject
GRB 221009A or Swift J1913.1+1946: PRIME near-infrared detection
Date
2022-10-10T12:15:59Z (3 years ago)
From
Igor Andreoni at JSI <igor.andreoni@gmail.com>
J. M. Durbak (UMD), A. S. Kutyrev (NASA/GSFC), I. Andreoni (JSI), K. De
(MIT), E. Troja (U Tor Vergata/ASU), S. B. Cenko (NASA/GSFC), R. Hamada
(Osaka U), Y. Hirao (Osaka U), R. Kirikawa (Osaka U), I. Kondo (Osaka U),
S. Miyazaki (ISAS/JAXA), G. Mosby (NASA/GSFC), T. Sumi (Osaka U), D. Suzuki
(Osaka U), H. Yama (Osaka U)

We observed the field of the transient Swift J1913.1+1946 or GRB 221009A
(Dichiara et al., GCN 32632; Kennea & Williams, GCN 32635; Veres et al.,
GCN 32636; Bissaldi et al., GCN 32637; Svinkin et al., GCN 32641; Ursi et
al., GCN Circ. 32650) with the PRIME near-infrared camera mounted on the
1.8m Telescope at SAAO.

Observations were carried out on 2022-10-09 around 18:50 UT, i.e. about 4.7
hours from the Swift/BAT detection (Dichiara et al., GCN 32632), 5.5 hours
after the Fermi/GBM detection (Veres et al., GCN 32636), and 1 day after
the PRIME instrument first light.

We detected a near-infrared source spatially consistent with the bright
optical transient previously reported, with preliminary photometry H~12.2
mag, calibrated against nearby 2MASS sources. Our result is consistent with
the REM detection (Brivio et al. GCN 32652) and suggests no significant
fading between 5.5 hr and 10.5 hr after the GBM trigger.

Archival deep near-infrared images of the field taken with WFCAM during the
UKIRT Galactic plane survey (Lawrence et al., 2007) do not show any
persistent source in J and H bands at the transient location.


These results are based on data obtained from PRIME at the South African
Astronomical Observatory (SAAO), Sutherland, South Africa.

GCN Circular 32655

Subject
GRB221009A/Swift J1913.1+1946: ATA follow-up observations
Date
2022-10-10T12:32:57Z (3 years ago)
From
Lauren Rhodes at Oxford <lauren.rhodes@physics.ox.ac.uk>
Wael Farah (SETI Institute), Joe Bright (University of Oxford), Alex Pollak, Andrew Siemion (SETI Institute), David DeBoer (UC Berkeley), Rob Fender, Lauren Rhodes, Ian Heywood (University of Oxford) report:

After the detection of a bright radio counterpart to GRB221009A at 15.5 GHz was reported in ATel #15653 /GCN #32653, we conducted follow-up observations with the Allen Telescope Array (ATA) at 1.5, 3, 4, 6, 8, and 10 GHz. Observations were carried out simultaneously at 1.5 + 3, 4 + 6 and 8 + 10 GHz, with a 672 MHz bandwidth centered on each frequency, using a newly deployed wideband correlator (Farah et al., in prep.), at spectral and temporal resolution of 0.5MHz and 10s, respectively. The target field was observed for 1 hour per pair of frequencies. The primary flux standard 3c286 was used to calibrate the absolute flux scale and bandpass response of the array, and J1925+2106 was used to calibrate the time dependent complex gains. Data flagging was performed with AOFlagger (Offringa+2012) while calibration and imaging were performed using standard techniques in CASA (McMullin+2007).

We clearly detect an unresolved radio source at a position consistent with the one reported in ATel #15650 at 1.5, 3, 6, 8, and 10 GHz. Preliminary flux densities at 3, 6, 8, and 10 GHz are reported below, and include a 10% absolute flux scale uncertainty in addition to the statistical error from the fit. Observations conducted at 4 GHz were severely corrupted by radio frequency interference and were not processed. Our observations indicate that the radio counterpart to GRB221009A/Swift J1913.1+1946 is self-absorbed below around 10 GHz, although there is apparently significant flux density evolution between observing epochs.


MJD                     Frequency (GHz)     Flux density (mJy)
59862.0492         3.0                           3.6 +/- 0.7
59861.9414         6.0                           9.0 +/- 1
59862.1242         8.0                           28  +/- 3
59862.1242         10.0                         38  +/- 4


The Allen Telescope Array is a 42-element radio interferometer located at the Hat Creek Radio Observatory in Northern California. The facility is fully operated by the SETI Institute.

GCN Circular 32657

Subject
GRB 221009A (Swift J1913.1+1946): AGILE/GRID detection
Date
2022-10-10T12:49:03Z (3 years ago)
From
Alessandro Ursi at INAF/IAPS <alessandro.ursi@gmail.com>
G. Piano (INAF/IAPS), F. Verrecchia (SSDC, and INAF/OAR), A. Bulgarelli
(INAF/OAS-Bologna), A. Ursi (INAF/IAPS), G. Panebianco (INAF/OAS-Bologna),
C. Pittori, (SSDC, and INAF/OAR), F. Longo (Univ. Trieste and INFN
Trieste), N. Parmiggiani (INAF/OAS-Bologna), M. Tavani (INAF/IAPS, and
Univ. Roma Tor Vergata), A. Argan, M. Cardillo, C. Casentini, Y.
Evangelista, L. Foffano, E. Menegoni, (INAF/IAPS), F. Lucarelli (SSDC, and
INAF/OAR), A. Addis, L. Baroncelli, A. Di Piano, V. Fioretti, F. Fuschino
(INAF/OAS-Bologna), M. Romani (INAF/OA-Brera), M. Marisaldi
(INAF/OAS-Bologna, and Bergen University), M. Pilia, A. Trois
(INAF/OA-Cagliari), I. Donnarumma (ASI), A. Giuliani (INAF/IASF-Mi), and P.
Tempesta (TeleSpazio), report on behalf of the AGILE Team:

The GRID detector onboard the AGILE satellite detected the bright emission
classified as GRB 221009A or Swift J1913.1+1946, reported by Swift BAT (GCN
#32635) at T0 = 2022-10-09 13:16:59 (UTC), by Fermi GBM (GCNs # 32636,
#31782), Fermi LAT (GCN #32637), IPN (GCN #32641), AGILE/MCAL (GCN #32650),
Swift XRT (GCN #32651), and Swift UVOT (GCN #32656).

Integrating from 2022-10-09 UT 13:16:59 (T0) to 2022-10-09 UT 14:16:59 (T0
+ 1h), a preliminary multi-source likelihood analysis yields a detection
with a significance of 42 sigma and a gamma-ray flux F(>100 MeV) = (1.11
+/- 0.08) x 10^-3 photons/cm^2/s, by adopting a power-law model with a
(reference) photon index value of -2.1.

The angular position of the gamma-ray event, as detected by the AGILE/GRID,
is:

(l, b) =  (52.99, 4.26) +/- 0.17 deg (stat.) +/- 0.10 deg (syst.)

These measurements were obtained with AGILE observing a large portion of
the sky in spinning mode. Additional analysis of AGILE data is in progress.

GCN Circular 32658

Subject
GRB 221009A: Fermi-LAT refined analysis
Date
2022-10-10T13:42:46Z (3 years ago)
From
Roberta Pillera at Politecnico and INFN Bari <roberta.pillera@ba.infn.it>
GRB 221009A: Fermi-LAT refined analysis

R. Pillera (Politecnico and INFN Bari), E Bissaldi (Politecnico and INFN 
Bari),
N. Omodei (Stanford Univ.), G. La Mura (LIP, Portugal),
F. Longo (University and INFN Trieste) report on behalf of the Fermi-LAT 
team:


We report updated observations of GRB 221009A which was detected by
Swift (Kennea et al. GCN #32635), Fermi-GBM (Veres et al. GCN #32636,
Lesage et al. GCN #32642), Fermi-LAT (Bissaldi et al. GCN #32637),
and the IPN (Svinkin et al. GCN #32641).

GRB 221009A triggered Fermi-GBM on October 10, 2022, at 13:16:59.99 UT
(trigger 687014224/221009553), about 1 hour earlier with respect
to the Swift trigger,  which was reported as a new bright
hard X-ray and optical transient and tentatively classified
as Swift J1913.1+1946 (Dichiara et al., GCN 32632).
Prompt GCN notices from Fermi-GBM were not distributed
due to problems with the real-time downlink from TDRS,
therefore no automatic Fermi-LAT GRB pipelines were triggered
by the GBM event.

Using LAT events with E>100 MeV between T0+200 s and T0+800 s,
we find a LAT localization of

RA = 288.282, Dec = 19.495,

with a 90% containment radius of 0.027 degrees (statistical only).

The LAT lightcurve shows a bright structured emission episode
which is temporally coincident with the GBM main emission episode
starting at T0+200s.
The 100 MeV - 1 GeV photon flux in the time interval 200-800 s after
the GBM trigger is (6.2 +/- 0.4)E-03 ph/cm2/s.
The estimated photon index above 100 MeV is -1.87 +/- 0.04.

 From a preliminary analysis, the LAT emission
is extending for about 25ks post GBM trigger.
The highest-energy photon is 99.3 GeV (with a probability of 99.2%)
which is observed 240 seconds after the GBM trigger.
This represents the highest GRB photon energy
ever detected by Fermi-LAT (the previous record holder being
a 95 GeV event from GRB 130427A).

The Fermi-LAT point of contact for this burst is
Elisabetta Bissaldi (elisabetta.bissaldi@ba.infn.it).

The Fermi-LAT is a pair conversion telescope designed to
cover the energy band from 20 MeV to greater than 300 GeV.
It is the product of an international collaboration
between NASA and DOE in the U.S. and many scientific
institutions across France, Italy, Japan and Sweden.

GCN Circular 32659

Subject
​GRB 221009A: Multi-color detection of the optical
Date
2022-10-10T14:16:00Z (3 years ago)
From
Gregory SungHak Paek at SNU <shpaek@astro.snu.ac.kr>
Gregory S.H. Paek (SNU ARC/SNU), Myungshin Im (SNU ARC/SNU), Yuji Urata
(NCU), Hyun-Il Sung (KASI) on behalf of a larger collaboration

 We detected the optical counterpart/NIR afterglow of extremely bright GRB
221009A (Dichiara et al., GCN #32632) with the 1-m class telescopes in
Lemonsan Optical Astronomy Observatory (LOAO) facilities of the GW
EM-Counterpart Korean Observatory (GECKO).

 We observed the center of UVOT localization (RA, Dec = 288.265, +19.774)
+15 hours after the report in B, V, R, I, z, and Y-bands. We clearly
detected the afterglow in all V, R, I, z, and Y-bands except for the
B-band. We calibrated flux with the PANSTARRS catalog and used an AB
magnitude system. Depth means 5 sigma upper limit for a point source
detection. The magnitudes are not corrected for galactic extinction.

------------------- ----------- ----------- ------ ----------- ----------
----- ------ -----
DATE-OBS[UTC]       JD          t-t0[days]  FILTER Observatory EXPTIME[s]
MAG   MAGERR DEPTH
------------------- ----------- ----------- ------ ----------- ----------
----- ------ -----
2022-10-10T04:18:54 2459862.680 0.626       B      LOAO        60s*5
 None   None  19.66
2022-10-10T04:20:38 2459862.681 0.628       V      LOAO        60s*5
 18.74  0.13  19.48
2022-10-10T04:22:04 2459862.682 0.629       R      LOAO        60s*5
 17.55  0.06  19.75
2022-10-10T04:23:31 2459862.683 0.630       I      LOAO        60s*5
 16.41  0.05  19.56
2022-10-10T04:24:39 2459862.684 0.631       z      LOAO        60s*5
 TBD    TBD   TBD
2022-10-10T04:25:58 2459862.685 0.631       Y      LOAO        60s*5
 TBD    TBD   TBD

 We will continue the follow-up observation for this target with the LOAO,
and other GECKO facilities in Australia, and Chile. Gravitational-wave EM
Counterpart Korean Observatory (GECKO) is a network of 10+ 0.5m to 1m class
telescopes worldwide.

GCN Circular 32660

Subject
GRB221009A/Swift J1913.1+1946: INTEGRAL SPI/ACS observations
Date
2022-10-10T14:52:36Z (3 years ago)
From
Diego Gotz at CEA <diego.gotz@cea.fr>
D. Gotz (CEA Paris Saclay), S. Mereghetti (INAF/IASF Milano), V. Savchenko, C. Ferrigno, E. Bozzo (ISDC Versoix) on behalf of the IBAS team report:

GRB221009A/Swift J1913.1+1946 (GCN 32635) has been detected in the SPI/ACS. 
It presents a multi-peaked structure with a first episode (precursor) staring at 13:16:58 UTC, peaking at 13:17:01 and lasting about 17 s.  

The GRB main episode starts at t_0 = 13:19:52 UTC and includes a complex multi-peaked structure, with three main peaks lasting about 460 s.

The fluence of the main episode is about 1.3e8 counts, which, based on the average conversion factor of Vigano' & Mereghetti 2009 (https://arxiv.org/abs/0912.5329 <https://arxiv.org/abs/0912.5329>), corresponds to 0.013 erg/cmsq in the 75 keV-1 MeV energy range.  This fluence value corresponds to an E_Iso of 8e53 erg (assuming a redshift z=0.151, GCN 32648).

We note that the fluence and E_Iso values are lower limits, due to the instrument saturation at the peak of the event.

The main episode if followed by a long tail with a power law time decay with index  of about  -1.6 and extending for at least 40 minutes after the precursor.

GCN Circular 32661

Subject
GRB221009A/Swift J1913.1+1946: Solar Orbiter STIX measurements
Date
2022-10-10T15:23:32Z (3 years ago)
From
Hualin Xiao at FHNW <hualin.xiao@fhnw.ch>
Hualin Xiao, S�m Krucker and Ryan Daniel on behalf of the STIX team report:


At 2020-10-09T13:16:56 UT (Solar Orbiter onboard time), STIX detected GRB221009A, when STIX was 1.22 AU from the earth.


The gamma-ray burst is clearly visible in the STIX quick-look light curves of five energy bands in the range between 4 -150 keV.



The initial pulse lasted about 10 seconds, followed by two bright pulses, lasting about 80 seconds.

The fourth pulse was detected at ~ 323 s after the initial pulse.

STIX recorded 185000 triggers from the burst in total.



STIX light curves can be found at: https://datacenter.stix.i4ds.net/pub/GRB/GRB221009A/stix_GRB221009A_light_curves.png

and  https://datacenter.stix.i4ds.net/view/ql/lightcurves


Solar Orbiter location during the GRB: https://datacenter.stix.i4ds.net/pub/GRB/GRB221009A/GRB221009A_solar_orbiter_orbit.png



The analysis results presented above are preliminary.  The science data will only be down-linked from the instrument in a month or two.  Detailed analysis of the event will be started after downloading the science data.


The Solar Orbiter (SolO) is a Sun-observing satellite developed by the European Space Agency, it was launched on 10th Feb. 2020.  It has a unique elliptical orbit around the sun, with distances varying from 0.3 - 1 AU. The Spectrometer Telescope for Imaging X-rays (STIX) is one of the ten instruments onboard the Solar Orbiter.  It measures X-rays emitted during solar flares in the energy range of 4 � 150 keV and takes X-ray images by using an indirect imaging technique, based on the Moir� effect.  Its detectors consist of thirty-two pixelated CdTe detectors with a total effective area of 6 cm^2.

More information about STIX can be found on the STIX data center website:  https://datacenter.stix.i4ds.net/

GCN Circular 32662

Subject
GRB 221009A / Swift J1913.1+1946: GIT detection of the optical afterglow
Date
2022-10-10T15:38:59Z (3 years ago)
From
Harsh Kumar at Indian Inst of Tech,Bombay <harshkosli13@gmail.com>
H. Kumar (IITB), V. Swain (IITB), G. Waratkar (IITB), K. Angail (IAO), V.
Bhalerao (IITB), G. C. Anupama(IIA), S. Barway (IIA) report on behalf of
the GIT team:

We observed Swift J1913.1+1946/GRB 221009A detected by Swift (S. Dichiara
et al., GCN #32632), Fermi (P. Veres et al., GCN #32636), INTEGRAL
(SPI-ACS) (Gotz et al., GCN #32660), and Konus-Wind (D. Svinkin et al., GCN
#32641), with 0.7m GROWTH-India Telescope (GIT). We obtained 200-sec
exposures in the g' and r' filters. We clearly detected the afterglow
candidate in our images at the position of Swift J1913.1+1946/GRB 221009A.
The photometric results follow as:

-------------------------------------------------------------------

 JD (mid) | T_mid-T0(hrs) | Filter | Magnitude (AB) |

-------------------------------------------------------------------

2459862.18181 | 2.19 | g' | 17.66 +/- 0.07 |

2459862.18451 | 2.25 | r' | 16.16 +/- 0.07 |

-------------------------------------------------------------------
The results are consistent with Lipunov et al., GCN #. 32634 and 32639;
Perley GCN #32638;  Broens, GCN #32640; Hu et al., GCN #32644; Belkin et
al. GCN #32645; de Wet et al. GCN #32646; Xu et al. GCN #32647; Odeh, GCN
#32649; Brivio et al. GCN # 32652. The magnitudes are calibrated against
PanSTARRS DR1 (Chambers et al., 2016) and not corrected for Galactic
extinction.

The GROWTH India Telescope (GIT) is a 70-cm telescope with a 0.7-degree
field of view, set up by the Indian Institute of Astrophysics (IIA) and the
Indian Institute of Technology Bombay (IITB) with funding from DST-SERB and
IUSSTF. It is located at the Indian Astronomical Observatory (Hanle),
operated by IIA. We acknowledge funding by the IITB alumni batch of 1994,
which partially supports the operations of the telescope. Telescope
technical details are available at
https://sites.google.com/view/growthindia/.

GCN Circular 32663

Subject
GRB221009A/Swift J1913.1+1946: SRG/ART-XC observation
Date
2022-10-10T15:51:44Z (3 years ago)
From
Sergey Molkov at Space Research Inst., Moscow <molkov@iki.rssi.ru>
I. Lapshov, S. Molkov, I. Mereminsky, A. Semena, V. Arefiev,
A. Tkachenko, A.Lutovinov (IKI RAS)
on behalf of the SRG/ART-XC team:

At 13:19:55 UT on 09 October 2022, the Mikhail Pavlinsky ART-XC
telescope on board the SRG observatory detected a strong burst
lasting few hundred seconds. Further analysis showed that the
source of emission was out of the field
of view of the instrument and the signal passed through the
telescope structure. We associate this event with a gamma-ray burst
GRB 221009A which was detected by Swift (Kennea et al. GCN #32635),
Fermi-GBM (Veres et al. GCN #32636, Lesage et al. GCN #32642),
Fermi-LAT (Bissaldi et al. GCN #32637, Pillera et al. GCN #32658),
the IPN (Svinkin et al. GCN #32641), SPI/ACS (Gotz et al. GCN #32660).

The ART-XC event corresponds to the second (brightest) burst episode
(see e.g. GCN #32642).
Since the radiation came out of the FoV, a prompt spectral analysis
of the event is impossible, however, due to the strong attenuation of
the signal passed through the surrounding matter, we register a
light curve shape that is practically not distorted by instrumental
effects such as deadtime, pile-up or telemetry problems. The light curve
in the full ART-XC energy range has a complex multi-peak structure
with two main maxima on 60th and 340th seconds from the start. The
event duration is near of 550 seconds.

GCN Circular 32664

Subject
GRB 221009A (Swift J1913.1+1946): Burke-Gaffney Observatory optical observations
Date
2022-10-10T16:21:51Z (3 years ago)
From
Filipp Dmitrievich Romanov at Amateur astronomer <filipp.romanov.27.04.1997@gmail.com>
I observed the optical afterglow of the extremely bright GRB 221009A =
Swift J1913.1+1946 (Dichiara et al., GCN Circ. 32632) remotely using
0.61-m f/6.5 Corrected Dall-Kirkham telescope of Burke-Gaffney
Observatory (Lane, 2018, RTSRE, 1, 119) on 2022-10-10. Twelve images
with exposures of 300 seconds and I�� filter were obtained, midtime of
the first image is 02:06:45 UTC (11h56m after the trigger), midtime of
the last image is 03:09:02 UTC (12h58m after the trigger).

I clearly detected the afterglow and measured (aperture photometry,
without deblending) following magnitudes of the afterglow from
comparison to transformed (from Lupton 2005 formula) magnitudes of
nearby stars from the Pan-STARRS DR1 catalogue (Chambers et al.,
2016):

Time (UTC)//Ic magnitude//Error
02:06:45  15.54  0.12
02:12:20  15.60  0.10
02:17:55  15.54  0.11
02:23:29  15.60  0.11
02:29:04  15.64  0.12
02:34:38  15.59  0.11
02:41:08  15.67  0.11
02:46:43  15.69  0.10
02:52:18  15.69  0.11
02:57:53  15.64  0.12
03:03:27  15.70  0.13
03:09:02  15.92  0.13

Magnitudes were not corrected for Galactic extinction.

FITS files available here:
https://observatory.smu.ca/~bgo/sm/id.php?app=0&id=20769 and
https://observatory.smu.ca/~bgo/sm/id.php?app=0&id=20770

Stacked image: https://observatory.smu.ca/~bgo/research/GRB_221009A.jpg

F. D. Romanov (AAVSO member, observer code: RFDA).

GCN Circular 32665

Subject
GRB 221009A: Upper limits from a neutrino search with IceCube
Date
2022-10-10T16:43:52Z (3 years ago)
From
Jessie Thwaites at IceCube/U Wisc-Madison <thwaites@wisc.edu>
The IceCube Collaboration (http://icecube.wisc.edu/) reports:


IceCube has performed a search for track-like muon neutrino events arriving from the direction of GRB 221009A (GCN Circular 32632<https://gcn.gsfc.nasa.gov/gcn3/32632.gcn3> (Swift);  32636<https://gcn.gsfc.nasa.gov/gcn3/32636.gcn3> (Fermi-GBM)) in a time range of -1 hour/+2 hours from the initial trigger reported by Fermi-GBM (T0=2022-10-09 13:16:59.99 UTC) during which IceCube was collecting good quality data. Zero track-like events are found coincident with the position of the GRB. We accordingly derive a time-integrated muon-neutrino flux upper limit for this source of E^2 dN/ dE = 3.9 x 10^-2 GeV cm^-2 at 90% CL, under the assumption of an E^-2 power law. 90% of events IceCube would detect from a source at this declination with an E^-2 spectrum have energies in the approximate energy range between 800 GeV and 1 PeV.


A subsequent search was performed including 2 days of data centered on the Fermi-GBM trigger (2022-10-08 13:16:59.99 UTC to 2022-10-10 13:16:59.99 UTC). In this case, we report a p-value of 1.0, consistent with background expectation. We accordingly derive a time-integrated muon-neutrino flux upper limit for this source of E^2 dN/ dE = 4.1 x 10^-2 GeV cm^-2 at 90% CL, under the assumption of an E^-2 power law.


The IceCube Neutrino Observatory is a cubic-kilometer neutrino detector operating at the geographic South Pole, Antarctica. The IceCube realtime alert point of contact can

be reached at roc@icecube.wisc.edu<mailto:roc@icecube.wisc.edu>.


[1] IceCube Collaboration, R. Abbasi  et al., ApJ 910 4 (2021)

GCN Circular 32667

Subject
GRB 221009A: Lulin SLT-40cm optical observations
Date
2022-10-10T20:05:50Z (3 years ago)
From
Ting-Wan Chen at MPE <janet.chen@astro.su.se>
T.-W. Chen (Stockholm), D. B. Malesani (Radboud Univ. and DAWN/NBI), S. Yang (Stockholm), W.-J. Hou, C.-C. Ngeow, Y.-C. Pan, H.-Y. Hsiao, C.-S. Lin, and J.-K. Guo (IANCU) report:

We observed the field of GRB 221009A (a.k.a. Swift J1913.1+1946; Dichiara et al., GCN 32632; Kennea & Williams, GCN 32635; Bissaldi et al., GCN 32637; Veres et al., GCN 32636; Lesage et al., GCN 32642; Gotz et al., GCN 32660), using the SLT-40cm at Lulin Observatory, Taiwan, to obtain g,r,i,z-band images as part of the Kinder collaboration (Chen et al., AstroNote 2021-92).

Observations started at 12:25 UT on 10 of October 2022 (MJD = 59862.518), 1.04 days after the Fermi GBM trigger time. The images were combined from 2 frames with 150 sec exposure time for each band, taken under variable seeing conditions (2".5 average) and at an airmass of 1.3.

We used aperture photometry to measure the transient brightness without template subtraction, and derived the following preliminary magnitudes and 3-sigma limits (all in the AB system):

g > 18.33 mag,
r = 18.67 +/- 0.16 mag,
i = 17.38 +/- 0.09 mag, and
z = 16.60 +/- 0.09 mag.

Given magnitudes are calibrated against Pan-STARRS1 field stars and are not corrected for the expected Galactic foreground extinction corresponding to a reddening of E_(B-V) = 1.40 mag in the direction of the counterpart (Schlafly & Finkbeiner 2011).

GCN Circular 32668

Subject
Konus-Wind detection of GRB 221009A
Date
2022-10-10T20:18:09Z (3 years ago)
From
Dmitry Frederiks at Ioffe Institute <fred@mail.ioffe.ru>
D. Frederiks, A.Lysenko, A. Ridnaia, D. Svinkin,
A. Tsvetkova,  M. Ulanov, and T. Cline,
on behalf of the Konus-Wind team, report:

The extraordinary bright GRB 221009A
(Fermi-GBM detection: Veres et al. GCN Circ 32636, Lesage et al. GCN Circ 32642;
Fermi-LAT detection: Bissaldi et al. GCN Circ 32637;
IPN triangulation: Svinkin et al. GCN Circ 32641;
AGILE/MCAL detection detection: Ursi et al., GCN Circ 32650)
triggered Konus-Wind (KW) at T0=47821.648 s UT (13:17:01.648).

The burst light curve starts with a FRED-like initial pulse (IP)
that lasts from ~T0-1 s to ~T0+25 s. The IP is followed by an extremely
bright multi-peaked emission in the interval from ~T0+170 s to ~T0+600 s,
where a preliminary-estimated count rate reaches several hundred counts/s.
The emission at this stage is seen up to at least ~15 MeV.
The pulsed phase of the burst evolves to a steadily decaying emission tail,
which is visible in the KW data for more than 10000 s.

The preliminary Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB221009_T47821/

A time-averaged spectrum of the IP (measured from T0 to T0+28.842 s)
is best fit in the 20 keV - 15 MeV range by a power law with exponential
cutoff (CPL) model: dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
with  alpha = -1.62(-0.04,+0.05) and Ep = 975(-332,+712) keV (chi2 = 80/98 dof).
The fluence in this time interval is estimated to (2.4 �� 0.3)x10^-05 erg/cm^2
and a 64-ms peak energy flux, measured from T0 + 5.760 s,
to (6.2 �� 0.7)x10^-6 erg/cm^2/s (both in the 20 keV - 10 MeV energy range).

A time-averaged spectrum at the onset of the brightest phase of the event
(measured from T0+180.48 to T0+200.064 s) is best fit in the 20 keV - 15 MeV range
by a GRB (Band) function with the following model parameters:
the low-energy photon index alpha = -1.09 (-0.01,+0.01),
the high energy photon index beta = -2.60 (-0.06,+0.06),
the peak energy Ep = 1060 (-30,+31) keV, chi2 = 161/97 dof.
The fluence in this time interval is estimated to (8.8 �� 0.1)x10^-04 erg/cm^2

The brightness of the main burst episode doesn't allow to perform
the standard KW spectral analysis of the emission at this stage of the event.
However, using the latter spectrum and a count rate light curve in the 80-320 keV range
with preliminary dead-time corrections applied, we obtain a rough estimate
of the fluence of the event in the interval from T0 to T0+600 s of ~0.052 erg/cm^2,
which is the highest value observed for GRBs for almost 28 years of the KW operation.
Further analysis of this extraordinary event is ongoing and
the results will be reported eslsewhere.

Assuming the redshift z=0.151 (de Ugarte Postigo et al., GCN 32648)
and a standard cosmology with H_0 = 67.3 km/s/Mpc, Omega_M = 0.315,
and Omega_Lambda = 0.685 (Planck Collaboration, 2014),
we estimate the burst isotropic energy release E_iso to a high,
but reasonable value of ~3.0x10^54 erg.
The rest-frame peak energy of the spectrum Ep,z is estimated to ~1150 keV.
With these preliminary values, GRB 221009A perfectly fits the
'Amati' relation for the sample of >300 long KW GRBs with known redshifts
(Tsvetkova et al., 2017; Tsvetkova et al., 2021),
see http://www.ioffe.ru/LEA/GRBs/GRB221009_T47821/GRB221009A_rest_frame.pdf

All the quoted errors are at the 68% confidence level.
All the presented results are preliminary.

GCN Circular 32669

Subject
GRB 221009A/Swift J1913.1+1946: Lick/Nickel telescope optical observations
Date
2022-10-10T20:34:25Z (3 years ago)
From
Weikang Zheng at UC Berkeley <weikang@berkeley.edu>
Edgar Vidal, WeiKang Zheng and Alexei V. Filippenko (UC Berkeley)

report on behalf of the KAIT GRB team:


We observed the field of GRB 221009A (=Swift J1913.1+1946; Dichiara et al.,

GCN 32632; Kennea & Williams, GCN 32635; Veres et al., GCN 32636; Bissaldi
et al.,

GCN 32637; Svinkin et al., GCN 32641; Ursi et al., GCN Circ. 32650;

Lesage et al., GCN 32642; Gotz et al., GCN 32660) with the 1-m Nickel
telescope

located at Lick observatory, California. Observations started about 15.73
hours

after the burst. Filtered B,V,R and I band images were taken with each
exposure

time of 300s. We detect the reported optical afterglow and measure its
brightness

with the following mag calibrated to the APASS catalog.


B = 20.18 +/- 0.2

V = 18.94 +/- 0.1

R = 17.59 +/- 0.1

I = 16.29 +/- 0.1


Additional images were also obtained with the 0.76-m Katzman Automatic
Imaging

Telescope (KAIT) also located at Lick Observatory. A set of clear (roughly
R)

band images were taken and the measured magnitude is consistent with the
above

Nickel R band magnitude.

GCN Circular 32670

Subject
GRB 221009A/Swift J1913.1+1946: Assy optical afterglow observation
Date
2022-10-10T22:04:05Z (3 years ago)
From
Alexei Pozanenko at IKI, Moscow <apozanen@iki.rssi.ru>
V. Kim (FAI), M. Krugov (FAI), A. Pozanenko (IKI), Y. Aimuratov (FAI), 
S. Belkin (IKI, HSE), N. Pankov (HSE) report on behalf of GRB IKI FuN:

We observed GRB 221009A/Swift J1913.1+1946 (Dichiara et al., GCN 32632; 
Kennea and Williams, GCN  32635; Veres et al., GCN  32636; Bissaldi et 
al., GCN  32636; Svinkin et al., GCN 32641; Piano et al., GCN 32657; 
Pillera et al., GCN 32658;  Gotz et al., GCN 32660;  Frederiks et al., 
GCN 32668)  with AZT-20 telescope of Assy-Turgen observatory starting on 
2022-10-10 (UT) 17:12:51. The observations were carried out sequentially 
with three images for 30 seconds, in each filter. In stacked images we 
clearly detect the optical afterglow (e.g. Dichiara et al., GCN 32632; 
Lipunov et al., GCN 32634; Perley GCN 32638; Hu et al., GCN 32644; 
Belkin  et al., GCN 32645; Kuin et al., GCN 32656). Preliminary 
photometry of the afterglow is following

Date       UT start  t-T0       Exp.   Filter  OT    Err.   UL(3sigma)
                     (mid, days)  (s)
2022-10-10 17:12:51  n/a        18*30  r'      18.64  0.03  20.8
2022-10-10 17:14:51  n/a        15*30  g'      20.53  0.11  21.1
2022-10-10 17:21:07  n/a        15*30  i'      17.58  0.01  20.7
2022-10-10 17:24:16  n/a        15*30  z'      16.87  0.05  19.8

The photometry is based on the nearby PS1 stars.

GCN Circular 32671

Subject
GRB 221009A: Continued Swift/XRT observations
Date
2022-10-10T22:17:35Z (3 years ago)
From
Aaron Tohuvavohu at U Toronto <aaron.tohu@gmail.com>
A. Tohuvavohu (U. Toronto), A.P. Beardmore (U. Leicester), J.P. Osborne
(U. Leicester), P. D'Avanzo (INAF-OAB), M.G. Bernardini (INAF-OAB), E.
Ambrosi  (INAF-IASFPA) , B. Sbarufatti (PSU), D.N. Burrows (PSU) and
M. Williams (PSU), report on behalf of the Swift-XRT team:

Swift XRT has continued to observe GRB 221009A  from 159s to 100 ks
after the BAT trigger. The WT-mode spectrum for the afterglow was
given in GCN 32651.

The lightcurve can be best modelled as a four-component power law decay with:
Alpha_1 : 2.6 (+0.4, -0.7)
Tbreak_1: 177.4 (+2.0, -9.6)
Alpha_2 : 0.144 (+0.022, -0.026)
Tbreak_2: 610 (+84, -78)
Alpha_3 : 0.31 (+0.04, -0.03)
Tbreak_3: (4.06 [+0.23, -0.19]) �� 10^3
Alpha_4 : 1.357 (+/-0.010)

With T0 the BAT trigger time.

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/01126853.

This circular is an official product of the Swift-XRT team.

GCN Circular 32676

Subject
GRB 221009A: NOEMA mm detection
Date
2022-10-11T09:09:27Z (3 years ago)
From
Antonio de Ugarte Postigo at OCA <deugarte@oca.eu>
A. de Ugarte Postigo (OCA), Michael Bremer (IRAM),
C. C. Thoene (ASU-CAS), M. Michalowski (AOI-AMU)
K. Misra (ARIES), S. Antier (OCA), D. A. Kann (Goethe 
Univ.), J. F. Agui Fernandez (IAA-CSIC), L. Resmi (IIST), 
S. Martin (ALMA), D. A. Perley (LJMU) and S. Schulze 
(Uni. of Stockholm) report,

We observed the afterglow of GRB 221009A (Dichiara et al., 
GCN 32632; Kennea & Williams, GCN 32635; Bissaldi et al., 
GCN 32637; Veres et al., GCN 32636; Lesage et al., GCN 
32642) with NOEMA at 90 and150 GHz starting at 16:32 UT 
of the 10th of October, (27.35 hr after the Fermi GBM trigger; 
Veres et al., GCN 32636). The afterglow is strongly detected 
at 90 GHz with a flux of ~15 mJy. This is significantly below 
the extrapolation of the data reported at lower frequencies in 
previous GCNs (Bright et al. GCN 32653; Farah et al., GCN 
32655), indicating that our observations are beyond the peak 
Frequency, and that the earlier observations may have been 
affected by a reverse shock that has already faded.

GCN Circular 32677

Subject
LHAASO observed GRB 221009A with more than 5000 VHE photons up to around 18 TeV
Date
2022-10-11T09:21:54Z (3 years ago)
From
Judith Racusin at GSFC <judith.racusin@nasa.gov>
Yong Huang, Shicong Hu, Songzhan Chen,  Min Zha, Cheng Liu, Zhiguo Yao and
Zhen Cao report on behalf of the LHAASO experiment

We report the observation of GRB 221009A, which was detected by Swift (Kennea
et al. GCN #32635), Fermi-GBM (Veres et al. GCN #32636, Lesage et al. GCN #32642),
Fermi-LAT (Bissaldi et al. GCN #32637), IPN (Svinkin et al. GCN #32641) and so on.

GRB 221009A is detected by LHAASO-WCDA at energy above 500 GeV, centered at
RA = 288.3, Dec = 19.7 within 2000 seconds after T0, with the significance above
100 s.d., and is observed as well by LHAASO-KM2A with the significance about 10 s.d.,
where the energy of the highest photon reaches 18 TeV.

This represents the first detection of photons above 10 TeV from GRBs.

The LHAASO is a multi-purpose experiment for gamma-ray astronomy (in the energy
band between 10^11 and 10^15 eV) and cosmic ray measurements.

GCN Circular 32678

Subject
GRB 221009A: BlackGEM optical observations
Date
2022-10-11T09:47:33Z (3 years ago)
From
Paul Groot at Radboud University Nijmegen <p.groot@astro.ru.nl>
P.J. Groot (Radboud/UCT/SAAO), P.M. Vreeswijk (Radboud), R. Ter Horst
(NOVA), S.D. Bloemen (Radboud), P.G. Jonker (Radboud/SRON), S. de Wet
(UCT), D.B. Malesani (Radboud and DAWN/NBI), D. Pieterse (Radboud)
report on behalf of the BlackGEM consortium:

During commissioning the BlackGEM Unit Telescope 3 (BG3-Opal), located
at ESO La Silla, Chile, observed the optical counterpart of GRB221009A
(Dichiara et al., GCN 32632, Lesage et al. GCN 32642, Lipunov et al.,
32634) on 2022-10-11 in a series of 60s exposures in the q,u,z,g,i,r,q
bands. No debiasing or flatfielding was performed.

The optical counterpart is detected in q,z,i:
2022-10-11 00:47UT q = 18.98 +/- 0.09 +/- 0.05 (T0+35h30m)
2022-10-11 00:50UT z = 16.92 +/- 0.05 +/- 0.03 (T0+35h33m)
2022-10-11 00:54UT i = 17.92 +/- 0.06 +/- 0.02 (T0+35h37m),
where the first uncertainty is the statistical uncertainty and the
second is the uncertainty on the zeropoint photometric calibration. T0
is taken as the Fermi/GBM trigger time 2022-10-09 13:17UT (Lesage et
al., GCN 32642). All magnitudes are in the AB system.

BlackGEM is an array of wide-field telescopes designed, built and
operated by a consortium consisting of Radboud University, the
Netherlands Research School for Astronomy NOVA, KU Leuven, the
University of Manchester, Tel Aviv University, the Weizmann Institute,
the Hebrew University of Jerusalem, the University of Potsdam, Texas
Tech University, the University of California at Davis, the Danish
Technical University and the Armagh Observatory and Planetarium.

GCN Circular 32679

Subject
GRB 221009A (Swift J1913.1+1946): iTelescope optical observation
Date
2022-10-11T10:03:35Z (3 years ago)
From
Filipp Dmitrievich Romanov at Amateur astronomer <filipp.romanov.27.04.1997@gmail.com>
I observed the optical afterglow of the extremely bright GRB 221009A =
Swift J1913.1+1946 (Dichiara et al., GCN Circ. 32632) remotely using
telescope T24 (0.61-m f/6.5 reflector + CCD) of iTelescope.Net in
Sierra Remote Observatory (Auberry, California, USA) on 2022-10-11.

Two images (exposures 300 seconds, BINx1) were obtained with Ic
filter, midtime of the stacked image is 06:12:42 UT (1d16h02m after
the trigger).

I clearly detected the afterglow and measured (aperture photometry,
without deblending) following magnitude: 17.1 Ic +/- 0.2 from
comparison to transformed (from Lupton 2005) magnitudes of nearby
stars from the Pan-STARRS DR1 catalogue (Chambers et al., 2016).

Magnitude was not corrected for the Galactic extinction.

Stacked image available here:
https://www.flickr.com/photos/filipp-romanov/52419866941

F. D. Romanov (AAVSO member, observer code: RFDA).

GCN Circular 32680

Subject
Swift/XRT discovery of multiple dust-scattering X-ray rings around GRB 221009A
Date
2022-10-11T10:37:56Z (3 years ago)
From
Sandro Mereghetti at IASF-Milano/INAF <sandro.mereghetti@inaf.it>
Andrea Tiengo (IUSS Pavia), Fabio Pintore (INAF IASF Palermo), Sandro
Mereghetti, Ruben Salvaterra (INAF IASF Milano)  on behalf of a larger
collaboration report:





Swift/XRT observed GRB221009A (GCN #32632, #32635, GCN #32636, #32637) in
PC mode three times (Obs.ID: 01126853004, 01126853005, 01126853006) between
2022-10-10 14:08:49 UT  and 2022-10-11 01:22:52 UT, for a net exposure time
of 7464.5 s.


The stacked Swift/XRT image in the 0.3-10 keV energy band shows the
presence of a complex system of at least 9 bright expanding rings with
radii from about 2.5 to 7.5 arcmin. We adopted the method described in
Tiengo & Mereghetti (2006, A&A 449, 203) to derive the following distances
of the dust clouds: 179.3 +/- 0.7 pc, 290 +/- 5 pc, 406.2 +/- 0.9 pc, 467.6
+/- 1.5 pc, 554 +/- 2 pc, 714 +/- 1 pc, 1094 +/- 24 pc,  2092 +/- 22 pc and
3635 +/- 36 pc.

GCN Circular 32683

Subject
GRB 221009A: Upper limits from HAWC 8 hours after trigger
Date
2022-10-11T12:04:14Z (3 years ago)
From
Hugo Ayala at Pennsylvania State University <hgayala@psu.edu>
Hugo Ayala  (PSU) reports on behalf of the HAWC
collaboration (http://www.hawc-observatory.org/collaboration)
reports observations of GRB 221009A which was detected by
Swift (Kennea et al. GCN #32635), Fermi-GBM (Veres et al. GCN #32636,
Lesage et al. GCN #32642), Fermi-LAT (Bissaldi et al. GCN #32637),
and the IPN (Svinkin et al. GCN #32641).

We use the position measured by Fermi LAT (GCN #32658), located at:
RA = 288.282, Dec = 19.495 (0.027 deg 90% containment radius)

This position started transiting over HAWC at 21:19:57 UTC on 2022/10/09
(~8 hours after the trigger time)  and ended at 03:42:07 UTC on 2022/10/10.

Assuming a power law spectra with index of -2.0 we found no significant
detection in the region. We proceeded to calculate the 95% upper limit on
the flux at 1 TeV: 4.16e-12 (TeV cm2 s)^-1

HAWC is a very-high-energy gamma-ray observatory operating in Central
Mexico at latitude 19 deg. north. Operating day and night with over
95% duty cycle, HAWC has an instantaneous field of view of 3.14 sr and
surveys <5/6 of the sky every day. It is sensitive to gamma rays from
300 GeV to 100 TeV.

GCN Circular 32684

Subject
GRB 221009A: Sintez-Newton/CrAO optical observations
Date
2022-10-11T13:01:20Z (3 years ago)
From
Alexei Pozanenko at IKI, Moscow <apozanen@iki.rssi.ru>
S. Belkin (IKI, HSE), S. Nazarov (CrAO), A. Pozanenko (IKI),  N. Pankov 
(HSE)  report on behalf of IKI GRB FuN:

We observed GRB 221009A/Swift J1913.1+1946 (Dichiara et al., GCN 32632; 
Kennea and Williams, GCN  32635; Veres et al., GCN  32636; Bissaldi et 
al., GCN  32636; Svinkin et al., GCN 32641; Piano et al., GCN 32657; 
Pillera et al., GCN 32658;  Gotz et al., GCN 32660;  Frederiks et al., 
GCN 32668)  with Sintez-Newton 350mm f/5 telescope equipped with QHY600M 
camera and g'r'i'z' filters.  Observation started on 2022-10-10 (UT) 
17:24:54. The series consists of images with an exposure of 120 s in 
r'-filter.

In the stacked image we clearly detect the optical afterglow (e.g. 
Dichiara et al., GCN 32632; Lipunov et al., GCN 32634; Perley GCN 32638; 
Hu et al., GCN 32644; Belkin  et al., GCN 32645; Kuin et al., GCN 32656; 
Kim et al., GCN 32670). Preliminary photometry of the afterglow is following


Preliminary photometry of the stacked images is following

Date       UT start   t-T0    Filter Exp.    OT    err   UL(3)
                      (mid, days)       (s)
2022-10-10 17:24:54   1.16293  r'    40*120  18.43 0.10  20.9

The photometry is based on nearby PS1 stars

GCN Circular 32685

Subject
GRB 221009A: Detection by GRBAlpha
Date
2022-10-11T13:24:38Z (3 years ago)
From
Jakub Ripa at Masaryk University <245487@mail.muni.cz>
J. Ripa (Masaryk U.), A. Pal (Konkoly Observatory), N. Werner (Masaryk 
U.), M. Ohno, H. Takahashi (Hiroshima U.), L. Meszaros, B. Csak (Konkoly 
Observatory), M. Dafcikova, F. Munz, N. Husarikova, J.-P. Breuer, M. 
Topinka, F. Hroch (Masaryk U.), T. Urbanec, M. Kasal,�� A. Povalac (Brno 
U. of Technology), J. Hudec, J. Kapus, M. Frajt (Spacemanic s.r.o), R. 
Laszlo, M. Koleda (Needronix s.r.o), M. Smelko, P. Hanak, P. Lipovsky 
(Technical U. of Kosice), G. Galgoczi (Wigner Research Center/Eotvos 
U.), Y. Uchida, H. Poon, H. Matake (Hiroshima U.), N. Uchida 
(ISAS/JAXA), T. Bozoki (Eotvos U.), G. Dalya (Eotvos U.), T. Enoto 
(Kyoto U.), Zs. Frei (Eotvos U.), G. Friss (Eotvos U.), Y. Fukazawa, K. 
Hirose (Hiroshima U.), S. Hisadomi (Nagoya U.), Y. Ichinohe (Rikkyo U.), 
K. Kapas (Eotvos U.), L. L. Kiss (Konkoly Observatory),�� T. Mizuno 
(Hiroshima U.), K. Nakazawa (Nagoya U.), H. Odaka (Univ of Tokyo), J. 
Takatsy (Eotvos U.), K. Torigoe (Hiroshima U.), N. Kogiso, M. Yoneyama 
(Osaka Metropolitan U.), M. Moritaki (U. Tokyo), T. Kano (U. Michigan) 
-- the GRBAlpha collaboration.

The extraordinarily bright long-duration GRB 221009A (Swift/BAT 
detection: Kennea et al., GCN 32635; Fermi-GBM detection: Veres et al., 
GCN 32636; Fermi-LAT detection: Pillera et al., GCN 32658; INTEGRAL 
SPI/ACS detection: Gotz et al., GCN 32660; Konus-Wind detection: 
Frederiks et al., GCN 32668; IPN triangulation: Svinkin et al., GCN 
32641; LHAASO detection: Huang et al., GCN 32677) at a redshift of z = 
0.151 (de Ugarte Postigo et al., GCN 32648) was detected by the GRBAlpha 
1U CubeSat (Pal et al. Proc. SPIE 2020).

The GRB did not saturate our detector and the peak count rate reached 
~22 000 count/s in the ~70-890 keV energy band (for a 50 cm^2 detector) 
at 2022-10-09 13:20:52 UTC. The duration of the GRB was >250s. GRBAlpha 
was flying above the northern polar region with elevated background 
levels. The end part of the GRB was recorded while passing the outer Van 
Allen radiation belt.

The light curve obtained by GRBAlpha is available here:
https://grbalpha.konkoly.hu/static/share/GRB221009A_GCN_GRBAlpha.pdf

GRBAlpha, launched on 2021 March 22, is a demonstration mission for a 
future CubeSat constellation (Werner et al. Proc. SPIE 2018). Its 
detector consists of a 75 x 75 x 5 mm^3 CsI(Tl) scintillator read out by 
a SiPM array, covering the energy range from ~50 keV to ~1000 keV. To 
increase the duty cycle and the downlink rate, we are continuously 
upgrading the on-board data acquisition software stack. The ground 
segment is also supported by the radio amateur community and it takes 
advantage of the SatNOGS network for increased data downlink volume.

GCN Circular 32686

Subject
GRB 221009A: 10.4m GTC spectroscopic redshift confirmation
Date
2022-10-11T13:37:44Z (3 years ago)
From
Alberto J. Castro-Tirado at IAA-CSIC <ajct@iaa.es>
A. J. Castro-Tirado, R. Sanchez-Ramirez, Y.-D. Hu, M.D. 
Caballero-Garcia, M. A. Castro Tirado, E. Fernandez-Garcia, I. 
Perez-Garcia (IAA-CSIC), G. Lombardi (GTC, IAC), S. B. Pandey (ARIES), 
J. Yang (NJU) and B.-B. Zhang (NJU) on behalf of a larger collaboration, 
report:

Following the detection of the extraordinarily bright GRB 221009A 
detected by Swift, Fermi, MAXI/GSC, INTEGRAL (SPI-ACS), Konus-Wind, the 
IPN, AGILE/MCAL, SolO/STIX, SRG/ART-XC, CALET and GRBAlpha (Dichiara et 
al. GCNC 32632, Veres et al. GCNC 32636, Bissaldi et al. GCNC 32637, 
Svinkin et al. GCNC 32641, Negoro et al. ATEL 15651, Ursi et al. GCNC 
32650, Xiao et al GCNC 32661, Lapshov et al. GCNC 32663, Cannady et al. 
GCNC 32674, Ripa et al. GCNC 32685), we triggered the 10.4m Gran 
Telescopio de Canarias (GTC) equipped with Optical System for Imaging 
and low-Intermediate-Resolution Integrated Spectroscopy (OSIRIS) in La 
Palma (Spain), starting on Oct 9, 22:19 UT (~9 hrs after the GBM 
trigger). Spectroscopy was obtained with both the R1000B (2x900s) and 
R1000R (2x300s) grisms, covering the 363-1000 nm spectral range. A red 
continuum is noticeable, in agreement with earlier reports by Perley 
(GCNC 32638) and Xu et al. (GCNC 32647). The GTC spectrum clearly shows 
the Ca II H & K absorption doublet implying a redshift of z=0.1505, 
consistent the value derived from X-shooter/VLT (de Ugarte Postigo et 
al. GCNC 32648). ��With this redshift of z= 0.1505, a time-averaged peak 
energy of 2.52 MeV and a total fluence of 2.6e-2 erg cm^-2, ��we found 
that the main emission episode (between 174 and 700 s post trigger) of 
GRB 221009A is consistent with the Type II (collapsar origin; Zhang et 
al, 2007, 2009) bursts in the Ep-Eiso diagram (Amati et al. 2002).

We thank the staff at GTC for their excellent support.

GCN Circular 32688

Subject
GRB 221009A (Swift J1913.1+1946): Swift-BAT refined analysis
Date
2022-10-11T14:12:57Z (3 years ago)
From
Amy Lien at GSFC <amy.y.lien@nasa.gov>
H. A. Krimm (NSF), S. D. Barthelmy (GSFC),
S. Dichiara (PSU), S. Laha (GSFC/UMBC),
A. Y. Lien (U Tampa), C. B. Markwardt (GSFC),
D. M. Palmer (LANL), T. Parsotan (GSFC/UMBC),
T. Sakamoto (AGU), M. Stamatikos (OSU)
(i.e. the Swift-BAT team):

Using the data set from T-239 to T+1371 sec from the recent
telemetry downlink, we report further analysis of BAT GRB 221009A
(trigger #1126853 and #1126854) (Dichiara et al., GCN Circ. 32632).
The BAT ground-calculated position is
RA, Dec = 288.254, 19.809 deg which is
   RA(J2000)  =  19h 13m 00.9s
   Dec(J2000) = +19d 48' 34.1"
with an uncertainty of 2.4 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 9%.

The mask-weighted light curve shows a flat and long-lasting emission
that may have started before the burst came into the BAT FOV at T-26 s.
The burst emission seems to end at ~T+1320 s, however, we cannot rule
out the possibility that the emission extends beyond the available
event data that end at T+1371 s. The lower limit of T90 (15-350 keV)
is 1068.40 +- 13.34 sec (estimated error including systematics).

The time-averaged spectrum from T+103.3 s to T+1338.7 s sec is best fit
by a simple power-law model.  The power law index of the time-averaged
spectrum is 2.08 +- 0.03.  The fluence in the 15-150 keV band
is 7.4 +- 0.1 x 10^-5 erg/cm2. The 1-sec peak photon flux measured
from T+776.47 sec in the 15-150 keV band is 1.9 +- 0.3 ph/cm2/sec.
All the quoted errors are at the 90% confidence level.

The results of the batgrbproduct analysis are available at
http://gcn.gsfc.nasa.gov/notices_s/1126853/BA/

GCN Circular 32690

Subject
GRB 221009A: planned observation with the Imaging X-ray Polarimetry Explorer (IXPE)
Date
2022-10-11T15:56:24Z (3 years ago)
From
Michela Negro at CREST/NASA-GSFC/UMBC <mnegro1@umbc.edu>
Michela Negro, Alberto Manfreda and Nicola Omodei on behalf

of the IXPE Collaboration report that:


IXPE will begin observing GRB 221009A on 2022-10-11 at

23:34:28.40 UTC and will observe for 100k s.

The detailed weekly timeline for IXPE observations (which

currently includes the slew to GRB 221009A) can be found here:

https://ixpe.msfc.nasa.gov/for_scientists/weekly.html


The Imaging X-ray Polarimetry Explorer, commonly known as IXPE

is a space observatory with three identical telescopes designed

to measure the polarization of cosmic X-rays. The observatory,

which was launched on 9 December 2021, is an international

collaboration between NASA and the Italian Space Agency (ASI).

GCN Circular 32691

Subject
GRB221009A: INTEGRAL detection of Hard X-ray emission up to 38 hours after trigger
Date
2022-10-11T16:05:23Z (3 years ago)
From
Volodymyr Savchenko at ISDC,U of Geneve <savchenk@in2p3.fr>
Volodymyr Savchenko (UNIGE, EPFL), Carlo Ferrigno, Enrico Bozzo (UNIGE), 
D. Gotz (CEA Paris Saclay), S. Mereghetti (INAF/IASF Milano),�� Antonio 
Martin Carrillo, Lorraine Hanlon (UCD), Elisabeth Jourdain, Jean-Pierre 
Roques (IRAP), Thomas Siegert (University of W��rzburg), Erik Kuulkers, 
Celia Sanchez (ESA)


Following the detection of the record-breaking GRB221009A by Swift/BAT 
(GCN #32632,#32635), Fermi/GBM (GCN #32636),
INTEGRAL/SPI-ACS (GCN #32660), we have performed INTEGRAL pointed 
observations of the GRB221009A location.

INTEGRAL pointed observation lasted from 2022-10-10T14:31:40 (T0 + 25.2 
hours, where T0 is 2022-10-09T13:17:00) to 2022-10-11T03:18:20 (T0 + 
38.0 hours) with a total exposure time of 30.2 ks (for ISGRI).

In the complete observation, the source is clearly detected in JEM-X1, 
JEM-X2 (3-30 keV), and ISGRI (28 - 80 keV), with S/N of 27.8, 27.3, 15.0 
respectively.

The joint JEM-X and ISGRI spectra can be satisfactorily modeled between 
3 and 80 keV with a single powerlaw of slope 2.15 +/- -0.07 (90% 
confidence) with a flux of 4.4e-10 +/- -2.1e-11 erg/cm2/s (3 - 80 keV).
This might indicate a single spectral component spanning from from hard 
X-ray to Fermi/LAT (GCN #32658).

Combination of bright Hard X-ray afterglow with gamma-ray emission was 
also found in GRB120711A (Martin-Carrillo et al. 2014 A&A 567, 84) and 
GRB130427A (Kouveliotou et al. 2013 ApJ 779L, 1K)
- in fact GRB221009A appears rather similar to GRB120711A, but at 10 
times smaller distance.

Within the relatively short JEM-X not ISGRI lightcurves, we do not 
observe any evidence for flux decrease.

Further INTEGRAL observations are scheduled between 2022-10-11 13:52:21 
and 2022-10-13 00:58:26. These observations will overlap with the 
planned observation of IXPE (GCN #32690).

We are grateful to the INTEGRAL Ground Segment team for quickly 
scheduling the observations.

Images and reduced data related to this publication can be found here: 
https://zenodo.org/record/7186289

GCN Circular 32692

Subject
GRB 221009A: COATLI Detection of the Afterglow
Date
2022-10-11T16:41:09Z (3 years ago)
From
Alan M Watson at UNAM <alan@astro.unam.mx>
Alan M. Watson (UNAM), Nat Butler (ASU), Simone Dichiara (PSU), Rosa L.
Becerra (UNAM), Tzveti Dimitrova (ASU), Oc��lotl L��pez (UNAM), Diego
Gonz��lez (UNAM), Alexander Kutyrev (GSFC), William H. Lee (UNAM),
Margarita Pereyra (UNAM), Eleonora Troja (UTV/ASU) and report:

We observed the field of the bright GRB 220930A (Dichiara et al., GCN
Circ. 32632, Veres et al., GCN Circ. 32636) with the COATLI 50-cm
telescope and HUITZI f/8 imager at the Observatorio Astron��mico Nacional
on the Sierra de San Pedro M��rtir (http://coatli.astroscu.unam.mx) from
2022-10-11 06:05 UTC to 06:39 UTC (40.2 hours after the trigger),
obtaining a total of 405 seconds of exposure in each of the g, r, i, and
z filters.

At the position of the UVOT afterglow (Dichiara et al., GCN Circ.
32632), we detect a source with the following magnitudes and 3-sigma
upper limit:

g > 20.27

r = 19.48 +/- 0.13

i = 18.49 +/- 0.07

z = 17.92 +/- 0.08

Our photometry is calibrated against the Pan-STARRS1 catalog, is on an
approximate AB system, and is not corrected for Galactic extinction in
the direction of the GRB.

We thank the COATLI/HUITZI technical team and the staff of the
Observatorio Astron��mico Nacional.

GCN Circular 32693

Subject
GRB 221009A: LCOGT Optical Afterglow Detection
Date
2022-10-11T17:04:03Z (3 years ago)
From
Robert Strausbaugh at University of Minnesota <rstrausb@umn.edu>
R. Strausbaugh (University of Minnesota), A. Cucchiara (NASA) report on
behalf of a larger collaboration:

We observed the GRB 221009A/Swift J1913.1+1946 (Dichiara et al., GCN 32632)
field with the LCOGT 1-meter Sinistro instrument at the Teide Observatory,
on Tenerife, on October 10, from 19:33 to 19:50 (corresponding to 29.38 to
29.66 hours from the GRB trigger time) with the SDSS g, r and i filters.

We performed a series of 3x100s exposures in each band.  We clearly detect
the optical transient at the UVOT coordinates (Dichiara et al., GCN 32632),
in r and i bands, and marginally in g-band (2-sigma detection), consistent
with other optical detections.

The following magnitudes are calculated using the Pan-STARRS catalog as
reference:

g = 20.87 +/- 0.36
r = 18.80 +/- 0.21
i = 17.77 +/- 0.20

These magnitudes are not corrected for galactic extinction.  Further
observations are planned.

GCN Circular 32694

Subject
GRB 221009A: NICER follow-up observations
Date
2022-10-11T18:41:54Z (3 years ago)
From
George A. Younes at George Washington U <gyounes@email.gwu.edu>
W. Iwakiri (Chuo U.), G. K. Jaisawal (DTU Space), G. Younes
(NASA/GSFC/GWU), Z. Wadiasingh (UMCP, NASA/GSFC), S. Guillot (IRAP/CNRS),
K. C. Gendreau (NASA/GSFC), Z. Arzoumanian (NASA/GSFC), E. C. Ferrara
(UMCP, NASA/GSFC), T. Mihara (RIKEN), D. Pasham (MIT), J. M. Miller (Univ.
of Michigan), A. Sanna (Univ. of Cagliari), C. Malacaria (ISSI), C. B.
Markwardt (NASA/GSFC)

We report on initial NICER observations of the exceptionally bright GRB
221009A, at a redshift of 0.1505 (GCN #32648, #32686) and observed from
radio to TeV energies (GCNs #32632, #32635, #32636, #32641, #32658, #32661,
#32668, #32677, and ATels #15653, #15655, #15656, #15660, #15661). NICER
observed GRB 221009A intermittently from 2022 Oct 9 17:11 to Oct 11 00:12
UT, or 14.7 ksec to 126 ksec after the Fermi/GBM trigger time (GCN #32636).
During this period, NICER made 12 observations with exposure times ranging
from 40 to 400 sec each. The initial count rate registered with NICER is
1400 counts/s which declined to about 38 counts/s at the time of the last
observation reported here. From a preliminary analysis, we find that the
decline follows a power law with an index of -1.6. The 1-10 keV spectrum of
each observation is well reproduced by an absorbed power-law model with a
spectral index of about 2.0. We used the tbabs model with wilms abundance
in XSPEC (Wilms, Allen & McCray 2000) for an assumed Galactic absorption of
5.4 x 10^21 cm^-2 (Willingale et al. 2013; GCN #32651). The average column
density of these observations with the ztbabs model is 1.1 x 10^22 cm^-2 at
a redshift of 0.151 (GCN #32648). The absorbed (unabsorbed) flux in the 0.3
- 10 keV band declined from 6.1 x 10^-9 (1.3 x 10^-8) to 1.8 x 10^-10 (3.3
x 10^-10) erg/sec/cm^2.

NICER initially received notification of the GRB through OHMAN (On-orbit
Hookup of MAXI and NICER) at 14:10:57 UT on Oct 9, but poor visibility
delayed a prompt follow-up.  OHMAN is software on an International Space
Station laptop computer that provides a new automated triggering
capability, monitoring live MAXI data and communicating new transient
alerts to NICER for follow-up within minutes, visibility permitting. NICER
is continuing to monitor GRB 221009A.  Detailed temporal and spectral
analysis is ongoing.

The NICER schedule can be found at
https://heasarc.gsfc.nasa.gov/docs/nicer/schedule/nicer_sts_current.html.

NICER is a 0.2-12 keV X-ray telescope operating on the International Space
Station. The NICER mission and portions of the NICER science team
activities are funded by NASA.

GCN Circular 32695

Subject
GRB 221009A: NuSTAR Detection
Date
2022-10-11T19:38:52Z (3 years ago)
From
Ryan Chornock at UC Berkeley <chornock@berkeley.edu>
Daniel Brethauer (UC Berkeley), Brian Grefenstette (Caltech), Judith Racusin (NASA/GSFC), Raffaella Margutti (UC Berkeley), Kate D. Alexander (Arizona), Tom Barclay (NASA/GSFC), Edo Berger (Harvard), Eric Burns (LSU), Brad Cenko (NASA/GSFC), Yvette  Cendes (Harvard), Ryan Chornock (UC Berkeley), Tarraneh Eftekhari (Northwestern), Jamie Kennea (PSU), and Tanmoy Laskar (Utah) report:

NuSTAR began a Target of Opportunity observation of GRB 221009A (GCN #32632) on October 11, 2022 at 03:10:07 UTC, approximately 38 hours after the GBM Trigger (GCN #32642), with an exposure of 23.4 ks (PIs Racusin and Margutti).

The 3-79 keV spectrum is well fit by a power law with a photon index of Gamma= 1.81 +/- 0.01, which is consistent with the value inferred from Swift-XRT observations acquired during the same time window.  The corresponding unabsorbed flux is (3.37 +/- 0.02) e-10 erg/cm2/s (3-79 keV). Over the NuSTAR observation, the source X-ray flux declines by about 30%. However, preliminary analysis does not indicate a significant evolution of the 10-20 keV / 3-6 keV hardness ratio.

These findings are consistent with the hard X-ray afterglow observed by INTEGRAL JEM-X and ISGRI (GCN #32691) and support an absorbed simple power-law spectrum extending from soft X-ray to hard X-ray energies. 

Three additional NuSTAR monitoring observations are planned and are anticipated to occur on October 15th, 20th, and November 2nd.  We thank the NuSTAR SOC for promptly implementing these observations.

GCN Circular 32700

Subject
GRB 221009A/Swift J1913.1+1946: eMERLIN observations
Date
2022-10-12T12:47:01Z (3 years ago)
From
Lauren Rhodes at Oxford <lauren.rhodes@physics.ox.ac.uk>
L. Rhodes, J. Bright, R. Fender (Oxford), and D.R.A. Williams (JBCA) report:



We observed the position of GRB 221009A (Swift J1913.1+1946; ATel #15650, ATel #15651) with the eMERLIN at 1.51GHz beginning at 17:55UT on 11th October for a total of 6 hours. OQ208 was used as the flux and bandpass calibrator while J1905+1943 was used as the complex gain calibrator.



We detect an unresolved source at a position consistent with the one reported in ATel #15651 with a (preliminary) flux density of ~4mJy.



We are in the process of obtaining further radio observations. We thank the e-MERLIN staff for the time allocation and their assistance with the observations.

GCN Circular 32705

Subject
GRB 221009A: COATLI Continued Monitoring of the Afterglow
Date
2022-10-12T15:23:25Z (3 years ago)
From
Alan M Watson at UNAM <alan@astro.unam.mx>
Nat Butler (ASU), Alan M. Watson (UNAM), Simone Dichiara (PSU), Rosa L.
Becerra (UNAM), Tzveti Dimitrova (ASU), Oc��lotl L��pez (UNAM), Diego
Gonz��lez (UNAM), Alexander Kutyrev (GSFC), William H. Lee (UNAM),
Margarita Pereyra (UNAM), Eleonora Troja (UTV/ASU) and report:

We observed the field of the bright GRB 221009A (Dichiara et al., GCN
Circ. 32632, Veres et al., GCN Circ. 32636) with the COATLI 50-cm
telescope and HUITZI f/8 imager at the Observatorio Astron��mico Nacional
on the Sierra de San Pedro M��rtir (http://coatli.astroscu.unam.mx) from
2022-10-12 04:00 UTC to 06:34 UTC (63.1 hours after the trigger),
obtaining a total of 7560 seconds of exposure in the i filter.

At the position of the UVOT afterglow (Dichiara et al., GCN Circ.
32632), we detect a source with the following magnitude:

i = 19.10 +/- 0.02

Our photometry is calibrated against the Pan-STARRS1 catalog, is on an
approximate AB system, and is not corrected for Galactic extinction in
the direction of the GRB.

Compared to our observations on the previous night (Watson et al., GCN
Circ. 32692), the decay has a power-law index of 1.24 +/- 0.13.

Further observations are planned.

We thank the COATLI/HUITZI technical team and the staff of the
Observatorio Astron��mico Nacional.

GCN Circular 32707

Subject
GRB 221009A/Swift J1913.1+1946: SMA observations
Date
2022-10-12T18:54:52Z (3 years ago)
From
Lauren Rhodes at Oxford <lauren.rhodes@physics.ox.ac.uk>
Lauren Rhodes (University of Oxford), Kuiyun Huang (CYCU/PCCU) and Yvette Cendes (Harvard) report on behalf of a larger collaboration:


We observed the field of the candidate gamma-ray burst GRB 221009A (Swift J1913.1+1946; ATel#15650, ATel#15651) with the Submillimeter Array (SMA) at 230.7GHz beginning at 03:27UT on 12 October 2022 for a total of 3.3 hours. Uranus was used as the flux calibrator, while 3c84 was used to calibrate the bandpass response. 1925+211 and mwc349a were used as interleaved complex gain calibrators.



We detect an unresolved source at a position consistent with the UVOT position reported in ATel #15650 at a (preliminary) flux density of 9.30 +/- 0.75mJy. Further observations are planned.



We thank the staff at the SMA for carrying out these observations.

GCN Circular 32709

Subject
GRB221009A: optical afterglow measurements from Konkoly Observatory
Date
2022-10-12T22:29:55Z (3 years ago)
From
Jozsef Vinko at Konkoly Observator <vinko@konkoly.hu>
J. Vinko, A. Bodi, A. Pal, L. Kriskovics, R. Szakats, K. Vida
(Konkoly Observatory, Hungary) report:

We observed the field of the bright GRB221009A (Dichiara et al., GCN #32632, Veres et al., GCN #32636)
with the RC80 robotic telescope at Piszkesteto Station of Konkoly Observatory on 2022 Oct 10.81 UT 
and Oct 12.85 UT, during inferior sky conditions. A series of 300 sec frames were collected through 
Sloan r'- and i' bands. The bright optical afterglow
(Lipunov et al. GCN #32634; Perley et al. GCN #32638; Broens GCN #32640; Hu et al. GCN #32644;
Belkin et al. GCN #32645; Wet et al. GCN #32646; Xu et al. GCN #32647; de Ugarte Postigo et al.
GCN #32648; Odeh GCN #32649; Brivio et al. GCN #32652; Kuin et al. GCN #32656;
Paek et al. GCN #32659; Kumar et al. GCN #32662; Romanov GCN #32664; Odeh GCN #32666;
Chen et al. GCN #32667; Vidal et al. GCN #32669; Kim et al. GCN #32670; Groot et al. GCN #32678;
Romanov GCN #32679; Castro-Tirado et al. GCN #32686; Watson et al. GCN #32692; Strausbaugh et al.
GCN #32693; Butler et al. GCN #32705)
was clearly detected on the stacked frames with the following magnitudes, calibrated
via nearby PS1 stars:

Date        UT-middle   t-T0(hr)  Exp(s)   r'(AB-mag)       i'(AB-mag)
2022-10-10  19:26:51    30.16     600      18.74 (0.12)     17.50 (0.08)
2022-10-12  20:18:24    79.02     300      20.58 (0.70)     18.74 (0.18)

These magnitudes are not corrected for galactic extinction.

GCN Circular 32727

Subject
GRB 221009A: GMG observation
Date
2022-10-13T03:01:54Z (3 years ago)
From
Jirong Mao at Yunnan Obs <jirongmao_obs@ynao.ac.cn>
J. Mao, K.-X. Lu, X.-H. Zhao, and J.-M. Bai (YNAO) report:




We observed the field of GRB 221009A (Dichiara et al. GCN 32632) with the 2.4-meter optical

telescope at Gao-Mei-Gu (GMG) station of Yunnan Observatories. The observation began at

UT 14:34:40, 12, Oct. 2022, about 3 days after the trigger. We marginally detected the

afterglow. The preliminary magnitude was measured to be z~18.9. We caution that the magnitude

has a relatively large uncertainty due to the very poor seeing.

GCN Circular 32729

Subject
GRB 221009A: Sayan observatory 1.6-m telescope observations
Date
2022-10-13T07:08:22Z (3 years ago)
From
Rodion Burenin at IKI, Moscow <rodion@hea.iki.rssi.ru>
I. Zaznobin, R. Burenin (IKI), M. Eselevich (ISTP SB RAS)

report:

The field of an extraordinarily bright GRB 221009A, detected by Swift
(Kennea et al., GCN 32635), Fermi GBM (Veres et al., GCN 32636),
SRG/ART-XC (Lapshov, et al., GCN 32663), Konus-Wind (Frederiks et al.,
GCN 32668), and others, was observed with the Sayan observatory
(Mondy) 1.6-m telescope AZT-33IK, using a CCD photometer, starting at
2022/10/10 13:38 UT, i.e. approximately 24.4 hours after the burst.

The optical transient found earlier (Dichiara et al., GCN 32632,
Lipunov et al., GCN 32634, Perley et al., GCN 32638, Belkin et al.,
GCN 32645, and others), was observed in griz filters with the
following magnitudes:

g = 20.57 +- 0.08
r = 18.84 +- 0.02
i = 17.80 +- 0.02
z = 16.99 +- 0.02

The decay in OT brigtness in all filters is observed during
approximately 2 hours of our observations.

Spectra of the OT in 3700--10000A wavelength range were also obtained
using ADAM low and medium resolution spectrograph. The analysis of
these data is underway.

GCN Circular 32730

Subject
GRB 221009A: MITSuME Okayama optical observation
Date
2022-10-13T07:58:56Z (3 years ago)
From
Yuri Imai at Tokyo Inst of Tech <imai@hp.phys.titech.ac.jp>
M. Sasada, Y. Imai, K. L. Murata, R. Hosokawa, M. Niwano, I.Takahashi,
M. Tateda, N. Ito, S. Sato, N. Higuchi, Y. Yatsu, and N. Kawai (Tokyo
Tech) report on behalf of the MITSuME collaboration:

We observed the field of GRB 221009A (Dichiara et al. #32632, Kennea
et al. #32635, Veres et al. #32636, Bissaldi et al. #32637, Perley et
al. #32638, Broens et al. #32640, Svinkin et al. #32641, Lesage et al.
#32642, Karambelkar et al. #32643, Hu et al. #32644, Belkin et al.
#32645, Wet et al. #32646, Xu et al. #32647, Postigo et al. #32648,
Ursi et al. #32650, Kennea et al. #32651, Brivio et al. #32652, Bright
et al. #32653, Durbak et al. #32654, Farah et al. #32655, Piano et al.
#32657, Pillera et al. #32658, Paek et al. #32659, Gotz et al. #32660,
Xiao et al.#32661, Kumar et al. #32662, Lapshov et al. #32663, Romanov
et al. #32664, The IceCube Collaboration et al. #32665, Odeh et al.
#32666, Chen et al. #32667, Frederiks et al. #32668, Vidal et al.
#32669, Kim et al. #32670, Tohuvavohu et al. #32671, Postigo et al.
#32676, Huang et al. #32677, Groot et al. #32678, Romanov et al.
#32679, Tiengo et al. #32680, Ayala et al. #32683, Belkin et al.
#32684, Ripa et al. #32685, Castro-Tirado et al. #32686, Krimm et al.
#32688, Negro et al. #32690, Savchenko et al. #32691, Watson et
al.#32692, Strausbaugh et al. #32693, Iwakiri et al. #32694, Brethauer
et al. #32695, Rhodes et al. #32700, Butler et al. #32705, Rhodes et
al. #32707, Vinko et al. #32709, Mao et al. #32727, Zaznobin et al.
#32729) with the optical three color (g', Rc, and Ic) CCD cameras
attached to the MITSuME 50 cm telescope Okayama.

The observation with a series of 60 sec exposures started at
2022-10-09 9:51:38 UT (0.857 day after the Swift detection). We
stacked the images with good conditions. Here we report a Ic-band
magnitude by the forced-photometry at the Swift/UVOT position
(Dichiara et al. GCN Circular #32632), and the 5-sigma limits of the
stacked images in the g' and Rc bands.

T0+[day] |MID-UT | T-EXP[sec] | magnitudes of forced-photometry
------------------------------------------------------------------------------------------------
0.9320 | 2022-10-10 11:39:09| 8340 | g'>18.3, Rc>17.0, Ic=17.1+/-0.2
------------------------------------------------------------------------------------------------
T0+ : Elapsed time after the burst
T-EXP: Total Exposure time

We used PS1 catalog for flux calibration. The magnitudes are expressed
in the AB system. The images were processed in real-time through the
MITSuME GPU reduction pipeline (Niwano et al. 2021, PASJ, Vol.73,
Issue 1, Pages 4-24; https://github.com/MNiwano/Eclaire).

GCN Circular 32736

Subject
GRB 221009A/Swift J1913.1+1946: low-frequency ASKAP observations
Date
2022-10-13T10:48:46Z (3 years ago)
From
James Leung at U of Sydney/VAST <jleu9465@uni.sydney.edu.au>
James Leung (University of Sydney/CSIRO), Emil Lenc (CSIRO), 
Tara Murphy (University of Sydney)

The Australian Square Kilometre Array Pathfinder (ASKAP) observed 
the field of GRB 221009A/Swift J1913.1+1946 (Dichiara et al., GCN
32632; Kennea & Williams., GCN 32635; Veres et al., GCN 32636) at 
888 MHz on 2022 October 12 from 07:00 to 13:00 UTC (2.70 to 2.95d
after the Swift/BAT trigger).

We detect an unresolved radio source at a position consistent with
the Swift/UVOT position (Dichiara et al., GCN 32632) with a 
preliminary flux density measurement of 2.2 +/- 0.1 mJy/beam.

We thank CSIRO staff for rapidly scheduling and supporting these
observations.

GCN Circular 32738

Subject
GRB221009A: LCOGT Continued Observations - Optical Upper Limits
Date
2022-10-13T16:00:24Z (3 years ago)
From
Robert Strausbaugh at University of Minnesota <rstrausb@umn.edu>
R. Strausbaugh (University of Minnesota), A. Cucchiara (NASA) report on
behalf of a larger collaboration:

We observed the GRB 221009A/Swift J1913.1+1946 (Dichiara et al., GCN 32632)
field with the LCOGT 1-meter Sinistro instrument at the McDonald
Observatory, Texas, USA site, on October 13, from 03:34 to 04:18
(corresponding to 84.60 to 85.50 hours from the GRB trigger time) with the
SDSS g, r, and i filters.

We performed a series of 3x300s exposures in each band.  We do not detect
the optical transient at the UVOT coordinates (Dichiara et al., GCN 32632),
in any bands.

The following upper limits are calculated using the Pan-STARRS catalog as
reference:

g > 22.3
r > 21.4
i > 20.5

These magnitudes are not corrected for galactic extinction.

GCN Circular 32739

Subject
GRB 221009A: Lowell Discovery Telescope Afterglow Detection
Date
2022-10-13T17:07:17Z (3 years ago)
From
Brendan O'Connor at UMD <oconnorb@umd.edu>
B. O'Connor (UMD/GWU), S. B. Cenko (NASA/GSFC), E. Troja (UTV/ASU),
S. Dichiara (PSU), A. Kutyrev (NASA/GSFC), S. Veilleux (UMD),
J. Durbak (UMD), on behalf of a larger collaboration:

We performed target of opportunity observations of GRB 221009A
(Dichiara et al., GCN 32632, Veres et al., GCN 32636)
with the 4.3m Lowell Discovery Telescope in Happy Jack, AZ.
Observations began on October 13, 2022 at 03:09:27 UT corresponding
to ~3.6 d after the GRB. We obtained images in the griz filters at
an airmass ~1.2 with seeing ~1.2".

The afterglow is clearly detected in all filters. We obtain the
following magnitudes calibrated against the PS1 catalog:

r = 20.44 +/- 0.02 AB mag
i = 19.37 +/- 0.01 AB mag

Compared to observations at 63 hr (Watson et al., GCN 32705)
the temporal decay has a power-law index of about -0.9,
shallower than observed in X-rays.

These magnitudes are not corrected for Galactic extinction.

We thank the staff of the Lowell Observatory for assistance
with these observations.

GCN Circular 32740

Subject
GRB 221009A: MeerKAT detection
Date
2022-10-13T17:34:58Z (3 years ago)
From
Tanmoy Laskar at U of Bath <tanmoylaskar@gmail.com>
T. Laskar (University of Utah), K. D. Alexander (Arizona), E. Ayache
(Stockholm), E. Berger (Harvard), S. Bhandari (ASTRON/JIVE), J. Bright
(Oxford), R. Chornock (UC Berkeley), D. Coppejans (Warwick), H. van Eerten
(Bath), W. Fong (Northwestern), P. Groot (Radboud), R. Margutti (UC
Berkeley), C.G. Mundell (Bath), P. Schady (Bath), G. Schroeder
(Northwestern), and S. de Wet (Cape Town) report:

"We observed GRB 221009A (Dichiara et al. GCN 32632) with the MeerKAT radio
telescope array beginning on 2022 October 10 19:10 UTC (1.3 d after the
burst). Preliminary analysis reveals a radio counterpart with 1.284 GHz
flux density of ~ 2.1 mJy at position:

RA (J2000) = 19:13:03.47 +/- 0.04"
Dec (J2000) = 19:46:25.08 +/- 0.06"

This position is consistent with the optical position (Dichiara et al., GCN
32632; Lipunov et al., GCN 32634). Further observations are planned.

The MeerKAT telescope is operated by the South African Radio Astronomy
Observatory, which is a facility of the National Research Foundation, an
agency of the Department of Science and Innovation."

GCN Circular 32741

Subject
GRB 221009A: search for neutrinos with KM3NeT
Date
2022-10-13T18:57:37Z (3 years ago)
From
Damien Dornic at CPPM,France <dornic@cppm.in2p3.fr>
The KM3NeT Collaboration (https://www.km3net.org/) reports:<br><br>
 
Using the data from the online fast processing chain, the KM3NeT Collaboration has performed a dedicated search for track-like muon neutrino events arriving from the direction of GRB 221009A (Dichiara et al. GCN 32632 (Swift);  Veres et al. GCN 32636 (Fermi-GBM)). The search covers the time range of [T0-50s, T0+5000s], with T0 being the trigger time reported by Fermi-GBM (T0=2022-10-09 13:16:59.00 UTC), during which both KM3NeT detectors were collecting good quality data. However, the GRB location was above the KM3NeT horizon (mean elevation of about ~40deg) during the search time window, significantly reducing the point-like source sensitivity. In both detectors, zero events were observed in the search window, while o(0.1) were expected from the background. The online fast processing uses preliminary calibrations and detector alignment, which will be superseded in a future elaborated analysis.<br><br>
 
A parallel search has been performed in the MeV range (Eur.Phys.J.C 82 (2022) 4, 317) without any significant neutrino coincidence.<br><br>
 
KM3NeT is a large undersea (Mediterranean Sea) infrastructure hosting two neutrino detectors, sensitive to burst of supernova neutrinos in the MeV range and to astrophysical neutrinos in the GeV-PeV energy range: ARCA at high energy and ORCA at low energy. A total of 21 and 11 detection lines are currently in operation in ARCA and ORCA, respectively.

GCN Circular 32743

Subject
GRB221009A: RTT-150 optical observations
Date
2022-10-13T20:12:07Z (3 years ago)
From
Rodion Burenin at IKI, Moscow <rodion@hea.iki.rssi.ru>
Ilfan Bikmaev (KFU, AST, Kazan), Irek Khamitov (TUG, Antalya, KFU, Kazan),
Eldar Irtuganov (KFU, AST, Kazan), Mark Gorbachev (KFU, AST, Kazan),
Nail Sakhibullin (KFU, AST, Kazan), Rodion Burenin (IKI, Moscow)

report:

We have performed optical observations of the OT GRB221009A (Dichiara
et al., GCN 32632, GCNs 32635, 32636,32636, 32641, 32657, 32658,
32660, 32666, 32668, 32670, 32671, 32676, 32677, 32678, 32679, 32680,
32683, 32684, 32685, 32686, 32691, 32692, 32693, 32694, 32695, 32700,
32705, 32707, 32709, 32727, 32729, 32730, 32736, 32738, 32739) by
using 1.5-meter joint Russian-Turkish telescope (RTT-150, TUBTAK
National Observatory, Antalya, Turkey) in October 10-12, 2022. We
used TFOSC instrument for photometry in griz filters and low
resolution spectroscopy in the 3800 - 8870 A range. During 3
consecutive nights starting 27.6 hours since the trigger we make
series of images in griz with 600 sec exposures each.

We clearly see the OT in all frames. Photometric data were calibrated
using nearby PS1 star. Results of our photometry are given in the
Table.

JD               T-T0    Filter  mag   merr
                 (hours)   
2459863.2056537  27.653  g      20.13  0.08
2459863.2131298  27.832  r      18.65  0.02
2459863.2205018  28.009  i      17.52  0.01
2459863.2278493  28.185  z      16.81  0.01
2459863.3452805  31.004  g      20.44  0.25
2459863.3681597  31.553  r      18.81  0.05
2459863.3760363  31.742  i      17.69  0.02
2459863.3840870  31.935  z      16.99  0.01   
2459864.1923863  51.334  r      19.53  0.04
2459864.2002009  51.522  i      18.40  0.02
2459864.2076914  51.702  z      17.69  0.02
2459864.2153146  51.884  g      21.15  0.21
2459864.3645166  55.465  r      19.67  0.11
2459864.3728065  55.664  i      18.49  0.04
2459864.3804310  55.847  z      17.72  0.03
2459865.2047148  75.630  i      18.82  0.03
2459865.2122502  75.811  r      20.03  0.06
2459865.2198393  75.993  z      18.20  0.04
2459865.2273203  76.173  i      19.02  0.07
2459865.2347618  76.351  r      19.97  0.08
2459865.2422699  76.531  z      18.19  0.05
2459865.2497386  76.711  i      19.09  0.10
2459865.2571590  76.889  r      20.07  0.19
2459865.2646685  77.069  z      18.40  0.08
2459865.2720521  77.246  i      18.95  0.07
2459865.2795044  77.425  r      20.32  0.17
2459865.2869724  77.604  z      18.26  0.03
2459865.2943683  77.782  i      18.93  0.04
2459865.3092743  78.140  z      18.23  0.03
2459865.3167266  78.318  i      18.93  0.04
2459865.3241129  78.496  r      20.17  0.12
2459865.3315775  78.675  z      18.23  0.04
2459865.3389639  78.852  i      18.92  0.04
2459865.3507442  79.135  r      20.26  0.16
2459865.3583217  79.317  z      18.30  0.04
2459865.3733491  79.677  r      20.24  0.19
2459865.3809028  79.859  z      18.18  0.04

Two series of low resolution (12 A) spectra were obtained in October
10, UT = 17:43 - 19:54 and in October 11, UT = 17:24 - 20:32.  Their
analysis is underway.

GCN Circular 32744

Subject
GRB221009A: Detection as sudden ionospheric disturbances (SID)
Date
2022-10-13T21:42:27Z (3 years ago)
From
Doug Welch at McMaster University <welch@physics.mcmaster.ca>
P.W. Schnoor (Kiel Longwave Monitor, Germany), P. Nicholson
(Todmorden, UK), D.L. Welch (McMaster University, Canada)

A sudden disturbance of the Earth's ionosphere (SID) was observed by the
Kiel Longwave Monitor (Germany) and a VLF-Monitor at Todmorden (near
Manchester, UK) coincident with the detection of GRB221009A (SWIFT, 
#32635).

This SID was seen as a sudden increase or decrease in the signal strengths
from radio transmitters below 100 kHz (19.6 to 63.9 kHz; VLF/LF) received
at Kiel and Todmorden.

These naval transmitting stations are located at France, Germany, Iceland,
Israel, Italy, Japan (Okinawa), United Kingdom and United States.

Note: This is not a radio detection of GRB221009A; this disturbance was
caused by the prompt X-rays and/or gamma-rays from GRB221009A
ionizing the upper atmosphere and modifying the radio propagation
properties of the waveguide between ground and ionosphere.

According to the SWIFT-BAT refined analysis (RA, Dec = 288.254, 19.809 deg,
GCN #32688) GRB221009A was above local horizon at both receiving sites
(2022-10-09, 13:16:59 UT).

Kiel:���������� az = 101.8, el = 32.9 deg
Todmorden: az = 94.6,�� el = 28.3 deg

Plots of the SID detection are available at the following URLs:

Kiel
https://www.qsl.net/df3lp/grb221009/KLM_grb221009a_magnitudes.png

Todmorden
http://abelian.org/vlf/grb221009a-DHO.png
http://abelian.org/vlf/grb221009a-NAA.png
http://abelian.org/vlf/grb221009a-NSY.png

The Kiel Longwave Monitor consists of a set of very low frequency radio
receivers attached to a crossed pair of loop antennas (16m^2 each),
monitoring the radio spectrum from 1.0 to 96.0 kHz at 50Hz-steps.

The VLF-monitor at Todmorden consists of a set of very low frequency radio
receivers attached to a crossed pair of loop antennas (20m^2 each) and a
vertical antenna, monitoring the radio spectrum below 100 kHz.

GCN Circular 32745

Subject
GRB221009A: Ionospheric disturbance observed in India
Date
2022-10-13T21:48:26Z (3 years ago)
From
Doug Welch at McMaster University <welch@physics.mcmaster.ca>
Authors: A. Guha (Centre for Lightning and Thunderstorm Studies (CeLTS), 
Department of Physics, Tripura University, India.), P. Nicholson 
(Todmorden, UK)

We report the observation of a sudden disturbance of radio propagation 
in the very low frequency (VLF) band between 18kHz and 23kHz coincident with
GRB221009A. Affected were phase and amplitude of MSK ("Minimum Shift 
Keying") signals from naval transmitters monitored by the Indian 
Lightning Detection Network.

The GRB221009A exceeded 70 degrees elevation at all receiver sites.

https://ildn.in/gallery/ILDN-GRB221009A-VTX3.png
https://ildn.in/gallery/ILDN-GRB221009A-NWC.png
https://ildn.in/gallery/ILDN-GRB221009A-NDT.png

The Indian Lightning Detection Network (ILDN) is an experimental network 
of 10 VLF receivers operated by collaborating institutions for lightning 
location and observation of other VLF phenomena on the Indian subcontinent.

GCN Circular 32746

Subject
GRB 221009A: Gamma-ray Detection by SIRI-2
Date
2022-10-14T00:18:42Z (3 years ago)
From
Lee Mitchell at Naval Research Laboratory <lee.mitchell@nrl.navy.mil>
L. J. Mitchell, B. F. Phlips, (Naval Research Laboratory), W.N. Johnson (Technology Service Corporation)



The SIRI-2 gamma-ray spectrometer (Mitchell et al. 2019, Proc. SPIE 11118) detected the bright long-duration GRB 221009A detected by Swift/BAT (Dichiara et al., GCN 32632, Kennea et al., GCN 32635), Fermi-GBM (Lesage et al., GCN 32642, Veres et al., GCN 32636), Fermi-LAT (Bissaldi et al. GCN 32637, Pillera et al., GCN 32658), AGILE-MCAL (Ursi et al., GCN 32650), AGILE-GRID (Piano et al. GCN 32657), INTEGRAL SPI/ACS (Gotz et al., GCN 32660), Konus-Wind (Frederiks et al., GCN 32668), at a redshift of z = 0.151 (de Ugarte Postigo et al., GCN 32648; Castro-Tirado et al., GCN 32686).



The GRB was 19.9 degrees off-axis from the un-collimated instrument. With 10-second binning, the background-subtracted peak count rates in the 300-7000 keV energy range were ~65e3 count/s and ~24e3 count/s from 2022-10-09 13:20:51-13:21:11  and 13:21:11-13:21:41 UTC, respectively, coinciding with the previously-reported brightest two gamma-ray peaks.  De-convolving the instrument response for the incident angle, the photon spectra for both peaks are consistent with a power law slope of -1.7 +/- 0.1.





SIRI-2 (Mitchell et al. 2019, Proc. SPIE 11118) was launched on 2021 DATE aboard the DoD Space Test Program's STPSat-6. It consists of seven hexagonal europium-doped strontium iodide (SrI2:Eu) scintillation detectors (each 3.81 cm by 3.81 cm), with a frontal area of 66 cm2, and read out by a SiPM array, covering the energy range of ~300 keV to ~7000 keV.

GCN Circular 32748

Subject
GRB 221009A: a 397.7 GeV photon observed by Fermi-LAT at 0.4 day after the GBM trigger
Date
2022-10-14T01:09:54Z (3 years ago)
From
Zi-Qing Xia at Purple Mountain Observatory <xiazq@pmo.ac.cn>
Zi-Qing Xia, Yun Wang, Qiang Yuan and Yi-Zhong Fan (Purple Mountain Observatory) report:

We have analyzed the long-term (MET: 687014224, 687139205) Fermi-LAT gamma-ray observations above 100 MeV of GRB 221009A, a burst characterized by its huge power, a low redshift as well as the highest energy photons (Kennea et al. GCN #32635, Veres et al. GCN #32636, Lesage et al. GCN #32642, Bissaldi et al. GCN #32637, Svinkin et al. GCN #32641, Huang et al. GCN #32677).

We find a 397.7 GeV photon at 0.27 degree from the LAT localization of GRB 221009A (RA = 288.282, Dec = 19.495, from Pillera et al. GCN #32658), arriving at 33554 seconds after the Fermi-GBM trigger. The location of this event is RA = 288.252, Dec = 19.763, which is close to the LHAASO localization of GRB 221009A (RA = 288.3, Dec = 19.7, from Huang et al. GCN #32677).

From a preliminary analysis, the 397.7 GeV event is found to be associated with GRB 221009A at a significance level of >3 sigma, which would be the most energetic GRB photon detected by Fermi-LAT so far (The previous records are a 99.3 GeV photon from GRB 221009A at an early time and a 95 GeV photon from GRB 130427A). Pre-GRB 221009A, just two photon events around 100 GeV had been observed by Fermi-LAT within 0.5 degree of GRB 221009A, suggesting a rather low chance coincidence probability of being a background. Furthermore, the GeV emission of GRB 221009A lasted more than one day.

The detection of such a high energy photon at t~0.4 day after the GRB trigger seems to favor the inverse compton origin rather than the synchrotron radiation (Fan et al. 2013 ApJ, 776, 95; https://arxiv.org/abs/1305.1261), which can reach very-high-energy domain in particular for the nearby luminous GRBs (Xue et al. 2009 ApJ, 703, 60; https://arxiv.org/abs/0907.4014).

GCN Circular 32749

Subject
GRB221009A: Gemini-South Optical Afterglow Detection
Date
2022-10-14T01:58:41Z (3 years ago)
From
Jillian Rastinejad at Northwestern Univ. <jillianrastinejad2024@u.northwestern.edu>
J. Rastinejad and W. Fong (Northwestern) report on behalf of a larger collaboration:

We observed the location of GRB 221009A (Dichiara et al. GCN 32632) with the Gemini Multi-Object Spectrograph (GMOS) mounted on Gemini-South under Program GS-2022B-DD-103 (PI: Rastinejad). We obtained 7x60-sec imaging in i-band at a mid-time of 2022 October 14 00:40:12 UT  (4.437 days post-burst), at a median airmass of 1.9. We clearly detect the optical afterglow. Calibrated to Panstarrs, we measure a brightness of i ~ 19.8 AB mag at seeing < 0.8'', not corrected for Galactic extinction. This is consistent with recently reported measurements (e.g. Bikmaev et al. GCN 32743) and indicates significant fading from the i-band measurement of 15.58 +/- 0.03 AB mag reported by de Wet et al. (GCN 32646) at 0.178 days. 

Further observations are planned to monitor the variability of the source. We thank Jennifer Andrews, Janice Lee, and additional Gemini staff for the rapid DDT approval, as well as the planning and execution of these observations.

GCN Circular 32750

Subject
GRB 221009A: Gemini-South Infrared Afterglow Detection
Date
2022-10-14T03:46:29Z (3 years ago)
From
Brendan O'Connor at UMD <oconnorb@umd.edu>
B. O'Connor (UMD/GWU), E. Troja (UTV/ASU), S. Dichiara (PSU),
J. Gillanders (UTV), S. B. Cenko (NASA/GSFC):

We performed target of opportunity observations of GRB 221009A
(Dichiara et al., GCN 32632, Veres et al., GCN 32636)
with the FLAMINGOS-2 spectrograph mounted on the Gemini-South
telescope. Observations began on October 13, 2022 at 23:58:42 UT
corresponding to ~4.4 d after the GRB. We obtained images in the
JHK filters with a total exposure of 60 s in each. The target
was at airmass 1.75 under seeing of ~0.7".

The afterglow is clearly detected in the JHK filters. We obtain
the following magnitudes calibrated against the 2MASS catalog:

J = 17.93 +/- 0.03 AB mag
H = 17.23 +/- 0.05 AB mag
K = 16.69 +/- 0.02 AB mag

Compared to previous nIR photometry (Brivio et al., GCN 32652,
Durbak et al. GCN 32654), our observation yields a power-law
decay with index ~ -1.4. This is steeper than reported in the
optical (O'Connor et al., GCN 32739) and consistent with that
observed in X-rays.

These magnitudes are not corrected for Galactic extinction.

Further infrared observations are planned.

We thank the staff (Janice Lee, Jennifer Andrews, and Jeong-Eun Heo)
of the Gemini Observatory for rapidly  approving and scheduling
these observations.

GCN Circular 32751

Subject
GRB 221009A: HEBS detection
Date
2022-10-14T10:09:17Z (3 years ago)
From
Dong Xu at NAOC/CAS <dxu@nao.cas.cn>
J. C. Liu, Y. Q. Zhang, S. L. Xiong, C. Zheng, C. W. Wang, W. C. Xue, R. 
Qiao, W. J. Tan, D. L. Zhang, X. Q. Li, X. Y. Wen, W. X. Peng, L. M. 
Song, S. J. Zheng, D. Y. Guo, X. B. Li, X. Ma, Y. Huang, X. Y. Zhao, P. 
Wang, J. Wang, Z. Zhang, Y. Q. Du, J. Liang, Y. Q. Lu, H. Wu, W. H. Yu, 
S. Xiao, C. Cai, P. Zhang, B. Li, Z. H. An, M. Gao, K. Gong, X. J. Liu, 
Y. Q. Liu, X. L. Sun, Y. B. Xu, S. Yang, P. Y. Feng, J. Z. Wang, F. 
Zhang, G. Chen, F. J. Lu, S. N. Zhang (IHEP) report on behalf of GECAM 
and HEBS teams:

During the commissioning phase, HEBS detected the prompt emission of the
extraordinarily bright burst GRB 221009A, which was also observed by
Fermi/GBM (Lesage et al., GCN 32642, Veres et al., GCN 32636),
Swift/BAT (Dichiara et al., GCN 32632, Kennea et al., GCN 32635)
Insight-HXMT/HE (Tan et al., Atel 15660),
Fermi/LAT (Bissaldi et al. GCN 32637, Pillera et al., GCN 32658),
AGILE/MCAL (Ursi et al., GCN 32650), AGILE/GRID (Piano et al. GCN 32657),
INTEGRAL SPI/ACS (Gotz et al., GCN 32660),
Konus-Wind (Frederiks et al., GCN 32668), SIRI-2 (Mitchell et al., GCN 
32746),
and LHAASO (Huang et al., GCN 32677).

At the beginning of the burst (2022-10-09T13:17:00.050 UTC, denoted as 
T0), HEBS was in the high latitude region where the in-flight triggering 
of HEBS was disabled to eliminate false triggers caused by particle 
background. However, one gamma-ray detector (i.e. GRD01) and one charged 
particle detector (i.e. CPD02) are set to collect data normally during 
this region. The full burst of GRB 221009A prompt emission was well 
monitored by HEBS. The incident angle to GRD01 is about 70 deg during 
the prompt emission.

Despite of the extreme brightness, the GRB 221009A main burst (T0+180s 
to T0+270s) was clearly observed by HEBS without data saturation. The 
dead-time is reasonable and the pulse pileup effect is negligible for 
the low gain readout channel of GRD01.

The dead-time corrected light curves of HEBS could be found at:
http://twiki.ihep.ac.cn/pub/GECAM/GRBList/HEBS-GRB221009A.png

 From the 50 ms light curve, we note that there are complicated spiky 
structures during the main peaks. All results above are preliminary. 
Refined analysis is ongoing and will be reported later.

HEBS is an all-sky monitor for gamma-ray transients in 10 keV to 5 MeV 
aboard the Space advanced technology demonstration satellite (SATech-01) 
satellite, which is funded and built by Chinese academic of sciences, 
and was launched on July 27, 2022. Both the payload and the science 
operation of HEBS are inherited from GECAM mission (made of two 
mini-satellites, GECAM-A and GECAM-B), and thereafter HEBS is also 
called GECAM-C.

GCN Circular 32752

Subject
GRB221009A: RTT-150 optical observations
Date
2022-10-14T11:03:17Z (3 years ago)
From
Rodion Burenin at IKI, Moscow <rodion@hea.iki.rssi.ru>
Ilfan Bikmaev (KFU, AST, Kazan), Irek Khamitov (TUG, Antalya, KFU, Kazan),
Eldar Irtuganov (KFU, AST, Kazan), Mark Gorbachev (KFU, AST, Kazan),
Nail Sakhibullin (KFU, AST, Kazan), Rodion Burenin (IKI, Moscow)

report:

We have performed additional optical observations of the OT GRB221009A
(Dichiara et al., GCN 32632, GCNs 32635, 32636,32636, 32641, 32657,
32658, 32660, 32666, 32668, 32670, 32671, 32676, 32677, 32678, 32679,
32680, 32683, 32684, 32685, 32686, 32691, 32692, 32693, 32694, 32695,
32700, 32705, 32707, 32709, 32727, 32729, 32730, 32736, 32738, 32739,
32740, 32743, 32746, 32749, 32750) by using 1.5-meter joint
Russian-Turkish telescope (RTT-150, TUBITAK National Observatory,
Antalya, Turkey) and TFOSC instrument in October 13, 2022. We made
series of images in riz filters with 600 sec exposures each.

We clearly see the OT in all frames. Photometric data were calibrated
using nearby PS1 star. Results of our photometry are given in the
Table:

JD                T-T0    Filter  mag   merr
                 (hours)   
2459866.2034967   99.601  r      20.53  0.09
2459866.2115203   99.793  i      19.51  0.06
2459866.2189183   99.971  z      18.63  0.05
2459866.2263488  100.149  r      20.63  0.09
2459866.2339414  100.332  i      19.41  0.05
2459866.2413937  100.510  z      18.76  0.05
2459866.2488331  100.689  r      20.71  0.15
2459866.2562889  100.868  i      19.52  0.05
2459866.2636921  101.046  z      18.69  0.04
2459866.2711805  101.225  r      20.54  0.10
2459866.2786139  101.404  i      19.44  0.04
2459866.2862528  101.587  z      18.75  0.04
2459866.2937201  101.766  r      20.55  0.12
2459866.3010995  101.943  i      19.45  0.05
2459866.3088004  102.128  z      18.74  0.05
2459866.3162909  102.308  r      20.74  0.16
2459866.3238331  102.489  i      19.43  0.05
2459866.3314625  102.672  z      18.83  0.05
2459866.3389523  102.852  r      20.90  0.23
2459866.3464004  103.031  i      19.48  0.06
2459866.3558217  103.257  z      18.74  0.05
2459866.3633150  103.437  r      20.86  0.27
2459866.3707428  103.615  i      19.50  0.07
2459866.3798291  103.833  z      18.71  0.06

RTT-150 light curves for 4 nights observations are shown in the Figure:

https://www.srg.cosmos.ru/static/images/grb/lc_grb221009A_RTT150.jpg


Power law decay indexes based on RTT-150 griz observations, taking in
account our data obtained earlier (Bikmaev et al., GCN 32743) are as
follows:

g:   -1.42 +- 0.20
r:   -1.47 +- 0.07
i:   -1.40 +- 0.04
z:   -1.38 +- 0.04

Our measurements of the OT power law decay agree well with that
measured in infrared bands (O'Connor et al., GCN 32750, Brivio et al.,
GCN 32652, Durbak et al. GCN 32654), obtained during nearly the same
periods of OT observations.

The mean value of (r - z) color indicates no any significant changes
in the optical spectrum slope during four nights of our observations.

GCN Circular 32753

Subject
GRB 221009A: OHP optical observations
Date
2022-10-14T12:40:52Z (3 years ago)
From
Benjamin Schneider at CEA <benjamin.schneider@cea.fr>
B. Schneider (CEA Paris-Saclay), C. Adami (LAM), E. Le Floc'h, 
D. Turpin, D. G��tz (CEA Paris-Saclay) S. D. Vergani, A. Saccardi 
(GEPI, Observatoire de Paris), S. Basa, A. Le Van Suu (LAM) report 
on behalf of a larger collaboration:

We observed the field of GRB 221009A (Dichiara et al., GCN 32632; 
Veres et al., GCN 32636) using the T120cm telescope at Observatoire 
de Haute-Provence (France). Four exposures were obtained in the 
r band (2x300s + 2x600s), three exposures in the i band (3x600s) 
and the z band (1x300s + 2x900s) from 2022 12 Oct 19:11:05 UT to 
2022 12 Oct 20:41:23 UT (mid time ~78h after trigger). In the 
combined frame, we clearly detect the source in the three filters 
and obtain the following magnitudes:

r = 20.23 �� 0.09 mag (AB)
i = 18.91 �� 0.11 mag (AB)
z = 18.35 �� 0.13 mag (AB)

The photometric calibration was performed using nearby stars from 
the PanSTARRS catalog and magnitudes are not corrected for Galactic 
extinction.

These values are consistent with observations obtained at a similar 
time by Bikmaev et al. (GCN 32743).

Further observations using the MISTRAL instrument mounted on the 
T193-OHP are planned for the coming nights.

We acknowledge the excellent support from Observatoire de Haute Provence, 
in particular Fran��ois Huppert and J��rome Schmitt.

GCN Circular 32754

Subject
GRB 221009A: IXPE preliminary upper limits of X-ray polarization
Date
2022-10-14T12:58:40Z (3 years ago)
From
Michela Negro at CRESST/NASA-GSFC/UMBC <mnegro1@umbc.edu>
Michela Negro, Alberto Manfreda, Nicola Omodei and 
Fabio Muleri report on behalf of the IXPE Collaboration 

IXPE performed the first observation of X-ray polarization of a 
GRB afterglow in the 2 ��� 8 keV energy range.
IXPE observed GRB 221009A from 2022-10-11T23:34:28UTC to 
2022-10-14T00:45:31UTC  for an effective exposure of 100 ks. 

From a quick-look analysis of the *image-, time- and energy- averaged
low-level instrument data (prior to pipeline processing at the IXPE
SOC), we report:

Polarization degree (PD) < 11.1% upper limits are derived with 99% C.L.

These results are preliminary. The IXPE Collaboration will report 
the final results in a forthcoming publication.

The Imaging X-ray Polarimetry Explorer, commonly known as IXPE 
is a space observatory with three identical telescopes designed 
to measure the polarization of cosmic X-rays. X-ray polarimetry 
enabled by IXPE can be performed in energy-, time-, and 
angle-resolved fashions. The observatory, which was launched 
on 9 December 2021, is an international collaboration between 
NASA and the Italian Space Agency (ASI).

[Editor's note: Reformatted at the request of the submitter.]

GCN Circular 32755

Subject
GRB 221009A: continued REM optical/NIR observations and evidence for an achromatic steepening in the afterglow light curve
Date
2022-10-14T14:29:16Z (3 years ago)
From
Paolo D'Avanzo at INAF-OAB <pda.davanzo@gmail.com>
P. D���Avanzo, M. Ferro, R. Brivio, M. G. Bernardini, D. Fugazza, S. Campana, S. Covino (INAF-OAB), V. D���Elia (ASI/SSDC), 
M. De Pasquale (Messina Univ.), D. B. Malesani (Radboud Univ. and DAWN/NBI), A. Melandri (INAF-OAR), E. Palazzi (INAF-OAS), 
S. Piranomonte (INAF-OAR), A. Rossi (INAF-OAS), B. Sbarufatti, G. Tagliaferri (INAF-OAB) on behalf of the REM team and of the 
CIBO collaboration, report:

We continued to observe the field of GRB 221009A (Dichiara et al., GCN 32632; Kennea & Williams, GCN 32635; Veres et al., GCN 32636; 
Bissaldi et al., GCN 32637; Svinkin et al., GCN 32641; Ursi et al., GCN Circ. 32650) with the REM 60cm robotic telescope located at the ESO 
premises of La Silla (Chile). The observations were carried in the optical and NIR bands, from about 0.4 to 3.5 days after the GBM trigger, 
with a nightly cadence. 

A refined analysis of the first REM epoch reveals that the H-band photometry reported in Brivio et al. (GCN Circ. 32652) is affected from 
contamination from a field star located at an angular separation of about 5" from the NIR afterglow. 
We report here an updated value of H = 12.62 +/- 0.02 mag (Vega, calibrated against the 2MASS catalogue) at 0.4 days after the GBM trigger. 

Inspection of the H- and z-band afterglow light curves obtained with REM reveals evidence for a steepening in the decay after about 1 day. 
We carried out a fit of the 0.3 - 10 keV Swift/XRT afterglow light curve (https://www.swift.ac.uk/xrt_curves/01126853/ <https://www.swift.ac.uk/xrt_curves/01126853/>), rescaling the t-t0 with 
respect to the time of the GBM trigger, and find statistical evidence that a broken power-law decay provides a better fit with respect to a single 
power-law decay, with a break time at about 1 day. 

By performing a joint fit to the H, z and X-ray bands, with a broken power-law model we find the the overall dataset is best fit with a broken 
power-law with decay indices alpha1_X ~ 1.5, alpha2_X ~ 1.9, alpha1_NIR = alpha1_opt ~ 0.8, alpha2_NIR = alpha2_opt ~ 1.6 with a break 
time (forced to be equal in all light curves) t_b ~ 0.98 days. 

Under the assumption that such an achromatic break is the GRB jet-break, starting from the computed GRB Eiso (Frederiks et al., GCN Circ. 32668) 
we obtain a jet half-opening angle theta_jet ~ 3.5 deg and a beaming-corrected energy for the GRB of ~ 6e51 erg (using efficiency 0.2 and density
 n = 1 cm^(-3); Sari et al., 1999, ApJ, 519, L17; Rhoads, 1999, ApJ, 525, 737 ).

GCN Circular 32756

Subject
MAXI/GSC refined analysis of the bright X-ray afterglow of GRB 221009A/Swift J1913.1+1946
Date
2022-10-14T14:29:30Z (3 years ago)
From
Hitoshi Negoro at Nihon U <negoro.hitoshi@nihon-u.ac.jp>
K. Kobayashi, H. Negoro, M. Nakajima, M. Tanaka, Y. Soejima (Nihon U.), 
T. Mihara, T. Kawamuro, S. Yamada, T. Tamagawa, M. Matsuoka (RIKEN), 
T. Sakamoto, M. Serino, S. Sugita, H. Hiramatsu, A. Yoshida (AGU), 
Y. Tsuboi, W. Iwakiri, J. Kohara (Chuo U.), M. Shidatsu, M. Iwasaki (Ehime U.),
N. Kawai, M. Niwano, R. Hosokawa, Y. Imai, N. Ito, Y. Takamatsu (Tokyo Tech), 
S. Nakahira,  S. Ueno, H. Tomida, M. Ishikawa,  T. Kurihara (JAXA), 
Y. Ueda, S. Ogawa, K. Setoguchi, T. Yoshitake, K. Inaba (Kyoto U.), 
M. Yamauchi, T. Sato, R. Hatsuda, R. Fukuoka, Y. Hagiwara, Y. Umeki (Miyazaki U.), 
K. Yamaoka (Nagoya U.), Y. Kawakubo (LSU), and M. Sugizaki (NAOC) 

We reported the MAXI/GSC detection of the bright X-ray emission 
from GRB 221009A/Swift J1913.1+1946 (GCN 32632/ATel #15650) 
at 13:58 (T0+2.5 ks, where T0 is the Fermi GBM trigger time, GCN 32642), 
15:31 (T0+8.0 ks), and 17:04 (T+13.6 ks) (ATel #15651).

Fitting GSC energy spectra at these scans with an absorbed power-law model 
gives a photon index of 1.93 +/- 0.09, 2.1 +/- 0.3, and 2.1 +/- 0.5, respectively. 
All the errors quoted are at the 90% confidence level. Here we fixed 
the column densities at 6.75e21 cm^-2 at z = 0.151 and 5.4e21 cm^-2 at z = 0 
obtained with the Swift XRT (GCN 32651). Unabsorbed 2-10 keV fluxes are 
(6.1 +/- 0.3)e-8 erg cm^-2 s^-1, (1.1 +/- 0.1)e-8 erg cm^-2 s^-1, and 
(0.7 +/- 0.1)e-8 erg cm^-2 s^-1, respectively.

We also note that the source was not detected in the transit at 12:25 UT 
on October 9 (T0-3.1 ks) with an upper limit of 20 mCrab.

We crosspost this report to the ATel and the GCN because we initially 
regarded this event as a galactic transient, and posted the preliminary results 
only to the ATel.

GCN Circular 32757

Subject
GRB 221009A: VLA detection
Date
2022-10-14T20:44:52Z (3 years ago)
From
Tanmoy Laskar at U of Bath <tanmoylaskar@gmail.com>
T. Laskar (Utah), K. D. Alexander (Arizona), E. Ayache (Stockholm), E.
Berger (Harvard), R. Chornock (Berkeley), H. van Eerten (Bath), W. Fong
(Northwestern), R. Margutti (Berkeley), C.G. Mundell (Bath), and P. Schady
(Bath) report:

"We observed GRB 221009A (Dichiara et al. GCN 32632) with the Karl G.
Jansky Very Large Array (VLA) beginning on 2022 October 12 23:08 UTC at
multiple frequencies (3.5 d after the burst). In preliminary analysis, we
detect the radio counterpart (Trushkin et al., ATEL 15671; Bright et al.,
GCN 32653; Farah et al., GCN 32655; Rhodes et al., GCN 32700; Leung et al.,
GCN 32836; Laskar et al., GCN 32740) with a flux density of ~ 9.2 mJy at 11
GHz, and position:

RA (J2000) = 19:13:03.50
Dec (J2000) = 19:46:24.23

with a (statistical) uncertainty of 0.01" in each coordinate. This position
is consistent with the optical position (Dichiara et al., GCN 32632;
Lipunov et al., GCN 32634) and the radio position (Laskar et al., GCN
32740). Further observations are planned.

We thank the VLA staff for scheduling and executing these observations"

GCN Circular 32758

Subject
GRB 221009A: Pan-STARRS optical photometry
Date
2022-10-14T21:35:08Z (3 years ago)
From
Ken Smith at Queen's University Belfast <k.w.smith@qub.ac.uk>
M. Huber, A. Schultz, K. C. Chambers (IfA, Hawaii), K. W. Smith,
M. Fulton, S. J. Smartt (QUB), T.-W. Chen (Stockholm), M. Nicholl
(Birmingham), D. R. Young, L. J. Shingles, S. Srivastav, S. Sim (QUB),
T. de Boer, J. Bulger, J. Fairlamb, C.-C. Lin, T. Lowe, E. Magnier,
R. J. Wainscoat, H. Gao (IfA), C. Stubbs (Harvard), A. Rest (STScI)

Daily imaging has been acquired (weather permitting) of the optical
counterpart of Swift J1913.1+1946 (Dichiara et al., GCN 32632;
Lipunov et al.,GCN 32634), the optical afterglow of GRB 221009A
(Kennea & Williams, GCN 32635; Veres et al., GCN 32636) with
Pan-STARRS2 since MJD 59863 (2022-10-11).  The following table
shows the most recent observations.

MJD          filter mag    dmag
59866.22756  r      20.92  0.05
59866.22504  i      19.88  0.02
59866.22371  z      19.21  0.02
59866.22239  y      18.77  0.03

We observed an initial fade of approximately 0.9 mags per day in
i, z and y, slowing to about 0.4 mags per day in these filters
over the last 2 days.

GCN Circular 32759

Subject
GRB 221009A: Large Binocular Telescope Observatory optical afterglow detection
Date
2022-10-15T00:09:35Z (3 years ago)
From
Manisha Shrestha at University of Arizona <mshrestha1@arizona.edu>
GRB 221009A: Large Binocular Telescope Observatory optical afterglow detection



M. Shrestha (Univ. of Arizona),  D. Sand (Univ. of Arizona), K. D. Alexander (Univ. of Arizona), J. Andrews (Gemini), J. Pearson (Univ. of Arizona), N. Smith (Univ. of Arizona), K. Bostroem (Univ. of Arizona)  report on behalf of a wider collaboration:


We observed the field of Swift GRB 221009A (Dichiara et al. GCN 32632 ) with the Large Binocular Telescope Observatory, located in Mount Graham, Arizona, on 2022 October 12 starting at 02:40:10.027 UT (~2.5 days after the trigger) using the MODS instrument in imaging mode in the g, i and z bands.  Data were calibrated with respect to nearby PanSTARRS catalog stars.



We clearly detect the optical counterpart in the i and z bands and obtain an upper limit on the g band. The magnitudes are as follows:

g    > 23

i  = 19.00 +- 0.02 mag

z = 18.26 +- 0.01 mag



These values are not corrected for galactic extinction and are consistent with (Butler et al. GCN 32705, Bikmaev et al. GCN 32743) which were obtained in similar time.



We would like to thank A Cardwell and LBTO staff for obtaining the observations.

GCN Circular 32760

Subject
GRB 221009A: Fermi LAT data rate effects due to extremely high flux
Date
2022-10-15T07:21:01Z (3 years ago)
From
Elisabetta Bissaldi at INFN,Bari <elisabetta.bissaldi@ba.infn.it>
N. Omodei (Stanford Univ.), P. Bruel (CNRS/IN2P3),
J. Bregeon (CNRS/IN2P3),  M. Pesce-Rollins (INFN Pisa),
D. Horan (CNRS/IN2P3),  E. Bissaldi (Politecnico and INFN Bari),
and R. Pillera (Politecnico and INFN Bari)
report on behalf of the Fermi-LAT team:


We report updated observations of GRB 221009A which was detected by
Swift (Kennea et al. GCN #32635), Fermi-GBM (Veres et al. GCN #32636,
Lesage et al. GCN #32642), Fermi-LAT (Bissaldi et al. GCN #32637,
Pillera et al. #32658), and the IPN (Svinkin et al. GCN #32641).

GRB 221009A triggered Fermi-GBM on October 9, 2022, at 13:16:59.99 UT
(T0, trigger 687014224/221009553).

During some time periods of the main emission episode of GRB 221009A
as seen in GBM, the LAT gamma-ray flux was so high that
more than one photon was recorded at the same time,
which strongly affected event reconstruction.
We are currently investigating the consequences of such a pile-up but,
until further notice, we discourage the use of LAT data in the time
intervals T0+225 to T0+236 seconds and T0+257 to T0+265 seconds
with respect to the GBM trigger time.

The photon with 99 GeV observed 240 seconds
after the GBM trigger is not affected by thesedata rate effects.

The Fermi-LAT point of contact for this burst is
Elisabetta Bissaldi (elisabetta.bissaldi@ba.infn.it).

The Fermi-LAT is a pair conversion telescope designed to
cover the energy band from 20 MeV to greater than 300 GeV.
It is the product of an international collaboration
between NASA and DOE in the U.S. and many scientific
institutions across France, Italy, Japan and Sweden.

GCN Circular 32761

Subject
GRB 221009A: ALMA and ACA detections
Date
2022-10-15T10:52:14Z (3 years ago)
From
Kuiyun Huang at CYCU <kuiyun@gmail.com>
Y. Urata, K.Y. Huang, S. Covino, K. Wiersema, K. Asada, H. Nagai,S.
Takahashi, K. Yamaoka, M. Tashiro, K.Toma, J. Shimoda, A. Kuwata and J.
Shimoda

We observed the field of GRB 221009A (Dichiara GCN 32632) with ALMAand ACA
at 97.5, 145, and 203 GHz.  The afterglow is significantly detected at all
bands, and the flux at 97.5 GHz was ~7 mJy at 4.3 days after the burst.
Together with the SMA measurements at the
similar epoch (Rhodes et al. GCN 32707), the spectrum seems to be flat
around the mm/submm band.

We thank ALMA staff for rapidly scheduling and supporting these
observations.

GCN Circular 32762

Subject
GRB 221009A: Armchair Energetics
Date
2022-10-15T13:52:06Z (3 years ago)
From
Alexander Kann at IAA-CSIC <kann@iaa.es>
D. A. Kann (Goethe Univ.) and J. F. Agui Fernandez (IAA) report:

The ultra-bright, nearby (de Ugarte Postigo et al., GCN #32648) GRB 
221009A (Swift (afterglow) discovery: Dichiara et al., GCN #32632) was 
so intense, it saturated multiple sensitive satellite detectors that 
registered the prompt emission (Fermi GBM: Veres et al., GCN #32636, 
Lesage et al., GCN #32642; Konus-Wind: Frederiks et al., GCN #32668; 
Fermi LAT: Omodei et al. GCN #32760; Agile/MCAL: Ursi et al. GCN #32650; 
INTEGRAL SPI/ACS, Gotz et al., GCN #32660; Insight-HXMT, Tan et al., 
ATel #15660).

Some missions detected GRB 221009A without saturation effects, because 
they are either smaller and less sensitive (GRBAlpha: Ripa et al., GCN 
#32685; SIRI-2: Mitchell et al., GCN #32746) or the burst was off-axis 
and passed through the spacecraft body (SRG ART-XC, Lapshov et al., GCN 
#32663). An especially interesting detection was made by HEBS (Liu et 
al., GCN #32751), which was also not saturated owing to its orbital 
position and environment.

Konus-Wind determined the energetics and spectrum of the first ("onset") 
pulse of the main emission episode (unsaturated, preceding the two 
brightest pulses), from T_0+180 - 200 s, finding a fluence of 8.8E-04 
erg cm^-2 (even this episode alone would be one of the brightest GRBs 
ever detected) and a peak energy of ~1 MeV. Using this spectrum and the 
raw, preliminarily corrected count rates of the other episodes, they 
determined a total fluence of 5.2E-02 erg cm^-2 (Frederiks et al., GCN 
#32668).

We take the count-rate light curve linked in the Konus-Wind GCN and 
determine the counts of the "onset" pulse, thereby determining a 
"fluence per count" conversion. With this value, and assuming the third 
episode of the GRB (from 380 to 610 s) is unsaturated (or corrected 
successfully) and has the same spectrum, we find a fluence of 1.28E-02 
erg cm^-2 for this episode. This is probably an overestimate, as the 
final episode of the GRB is likely softer (see the similar GRB 160625B, 
e.g., B.-B. Zhang et al. 2018, Nature Astronomy, 2, 69). For the HEBS 
data, we derive a significantly lower fluence of ~3E-03 erg cm^-2. A 
potential explanation is that the high background during the time of the 
GRB led to the softer bands being discarded, losing a lot of counts for 
the softer episode.

For the main episode (200 - 300 s), we derive a fluence of 7.65E-02 erg 
cm^-2 from the HEBS light curve, a value somewhat higher than the one 
derived for the entire burst from Konus-Wind. Again, this is dependent 
on the spectrum being the same as during the "onset" pulse. If it is 
even harder, the fluence would increase correspondingly.

Summing all together (the precursor is negligible), we derive, in a 
broad bolometric band from 0.1 keV to 100 MeV (see Agui Fernandez et 
al., 2021, MNRAS, submitted, arXiv:2109.13838), an isotropic energy 
release of log E_iso = 54.77, a value in perfect agreement with GRB 
160625B in the same band. This places GRB 221009A within the very 
highest isotropic energy releases measured so far. On the one hand, this 
implies the GRB is extreme but not an outlier, whereas, on the other 
hand, combined with the very low distance, it makes it an even rarer 
event.

GCN Circular 32763

Subject
GRB 221009A: ATCA detection
Date
2022-10-15T15:37:33Z (3 years ago)
From
Tanmoy Laskar at U of Bath <tanmoylaskar@gmail.com>
S. Bhandari (ASTRON/JIVE), T. Laskar (Utah), K. D. Alexander (Arizona), E.
Berger (Harvard), R. Chornock (Berkeley), D. Coppejans (Warwick), M. Drout
(Toronto), H. van Eerten (Bath), W. Fong (Northwestern), C. Guidorzi
(Ferrara), R. Margutti (Berkeley), C.G. Mundell (Bath), P. Schady (Bath)
and G. Schroeder (Northwestern) report:

"ATCA observed GRB 221009A (Dichiara et al. GCN 32632) beginning on 2022
October 15 05:00 UTC (5.7 d after the burst) at multiple frequencies. In a
preliminary analysis, we detect the radio counterpart (Trushkin et al.,
ATEL 15671; Bright et al., GCN 32653; Farah et al., GCN 32655; de Ugarte
Postigo et al., GCN 32676; Rhodes et al., GCN 32700; Rhodes et al., GCN
32707; Leung et al., GCN 32836; Laskar et al., GCN 32740; Laskar et al.,
GCN 32757; Urata et al., GCN 32761) with a flux density of ~ 6.8 mJy at
16.7 GHz at a position consistent with the optical position (Dichiara et
al., GCN 32632; Lipunov et al., GCN 32634) and the radio position (Laskar
et al., GCN 32740, Laskar et al., GCN 32757). Further observations are
planned.

We thank the CSIRO staff for approving and carrying out these observations.

The Australia Telescope Compact Array is part of the Australia Telescope
National Facility which is funded by the Australian Government for
operation as a National Facility managed by CSIRO. We acknowledge the
Gomeroi people as the traditional owners of the Observatory site."

GCN Circular 32765

Subject
GRB 221009A: VLT spectroscopic detection of the host galaxy
Date
2022-10-15T16:56:06Z (3 years ago)
From
Daniele B Malesani at Radboud U <d.malesani@astro.ru.nl>
L. Izzo (DARK/NBI), A. Saccardi (GEPI, Observatoire de Paris), J. P. U. 
Fynbo (DAWN/NBI), J. Palmerio (GEPI, Paris obs.), D. B. Malesani 
(Radboud Univ. and DAWN/NBI), J. F. Agui Fernandez (IAA/CSIC), D. A. 
Kann (Goethe Univ.), A. Melandri (INAF/OAR), S. D. Vergani (GEPI, Paris 
obs.), K. Wiersema (Lancaster univ.), report on behalf of the Stargate 
consortium:

We observed the optical counterpart of GRB 221009A (Dichiara et al., GCN 
32632; Veres et al., GCN 32636; and very many other GRB satellites) 
using the ESO VLT UT3 (Melipal) equipped with the X-shooter 
spectrograph. A 40-min spectrum was secured covering the wavelength 
range 3000-25000 AA, with a mean time 2022 October 14.02 UT (4.46 days 
after the Fermi/GBM trigger).

 From the acquisition image, we measure for the optical counterpart a 
magnitude i = 19.89 +- 0.05 (AB; calibrated against Pan-STARRS), 4.45 
days after the Fermi/GBM trigger.

The continuum is still dominated by the afterglow. However, narrow 
emission lines can be seen from the host galaxy. We identify H alpha in 
the optical and Pa alpha in the near-infrared, at redshift z = 0.151, 
consistent with the one measured from the afterglow absorption features 
(de Ugarte Postigo et al., GCN 32648).

The H alpha FWHM is about 110 km s^-1. From the H alpha flux, corrected 
for Galactic extinction (A_V = 4.2 mag), we infer a SFR > 0.25 M_Sun 
yr^-1 (this value is a lower limit due to unaccounted host extinction 
and slit losses).

We acknowledge expert support from the ESO observing staff in Paranal, 
in particular Zahed Wahhaj and Matias Jones.

GCN Circular 32766

Subject
GRB 221009A: ATCA radio spectrum
Date
2022-10-15T23:15:43Z (3 years ago)
From
James Leung at U of Sydney/VAST <jleu9465@uni.sydney.edu.au>
James Leung (University of Sydney/CSIRO), Tara Murphy (University of 
Sydney), Emil Lenc (CSIRO), Gemma Anderson (Curtin)

We report the radio spectrum for the Australia Compact Telescope Array 
(ATCA) observations (Bhandari et al., GCN 32763) taken on 2022 October
15 from 05:00 to 11:30 UTC (5.6 to 5.9d after the Swift/BAT trigger).

ATCA observed at 16.7, 21.2, 33, 35, 45 and 47 GHz. In our preliminary
analysis, we detect the radio counterpart at each frequency (Trushkin 
et al., ATel 15671; Bright et al., GCN 32653; Farah et al., GCN 32655; 
de Ugarte Postigo et al., GCN 32676; Rhodes et al., GCN 32700; Leung
et al., GCN 32836; Laskar et al., GCN 32740; Laskar et al., GCN 32757;
Urata et al., GCN 32761; Bhandari et al., GCN 32763) at a position 
consistent with the Swift/UVOT position (Dichiara et al., GCN 32632). 

The preliminary flux density measurements are reported below, with 
uncertainties being purely statistical:

7.1 +/- 0.1 mJy/beam at 16.7 GHz
6.1 +/- 0.1 mJy/beam at 21.2 GHz
4.8 +/- 0.1 mJy/beam at 33 GHz
4.4 +/- 0.1 mJy/beam at 35 GHz
3.6 +/- 0.2 mJy/beam at 45 GHz
3.5 +/- 0.2 mJy/beam at 47 GHz

Ongoing observations are planned. 

We thank CSIRO staff for rapidly scheduling, supporting and executing
these observations.

The Australia Telescope Compact Array is part of the Australia Telescope
National Facility which is funded by the Australian Government for
operation as a National Facility managed by CSIRO. We acknowledge the
Gomeroi people as the traditional owners of the Observatory site.

GCN Circular 32767

Subject
GRB 221009A: LEIA X-ray Afterglow Detection
Date
2022-10-16T02:21:05Z (3 years ago)
From
LEIA Team at NAOC/CAS <ep_ta@bao.ac.cn>
Y. Liu, C. Zhang, Z.X. Ling, H.Q. Cheng, C.Z. Cui, D.W. Fan, H.B. Hu,

M.H. Huang, C.C. Jin, D.Y. Li, H.Y. Liu, H. Sun, H.W. Pan, W.X. Wang,

Y.F. Xu, M. Zhang, W.D. Zhang, D.H. Zhao, and W. Yuan (NAOC, CAS),

report on behalf of the LEIA and Einstein Probe team:

 

LEIA (Lobster Eye Imager for Astronomy) has performed one

follow-up observation of GRB 221009A detected by Swift/BAT

(Dichiara et al., GCN 32632, Kennea et al., GCN 32635), Fermi-GBM

(Lesage et al., GCN 32642, Veres et al., GCN 32636), Fermi-LAT

(Bissaldi et al. GCN 32637, Pillera et al., GCN 32658), AGILE-MCAL

(Ursi et al., GCN 32650), AGILE-GRID (Piano et al. GCN 32657),

INTEGRAL SPI/ACS (Gotz et al., GCN 32660), Konus-Wind

(Frederiks et al., GCN 32668), HEBS (Liu et al., GCN 32751), at a 

redshift of z = 0.151 (de Ugarte Postigo et al., GCN 32648; 

Castro-Tirado et al., GCN 32686).

 

The pointed observation was conducted from 2022-10-12T05:31:48

to 2022-10-12T05:51:39 with a net exposure of 1012 s. The X-ray

afterglow of GRB 221009A is detected at a significance of 4.9 sigma.

Assuming an absorbed power-law model with a photon index of 2.0,

a Galactic absorption of 5.4 x 10^21 cm^-2 (Willingale et al. 2013;

GCN #32651), and an intrinsic absorption of 1.1 x 10^22 cm^-2 at a

redshift of 0.151 (GCN #32648), the unabsorbed flux in the 0.5 - 4.0 keV

band is (1.8+/-0.4) x 10^-10 ergs/cm^2/s.

 

LEIA (Zhang et al, ApJL submitted) is a soft X-ray monitor (0.5 - 4.0 keV)

with a FoV of 340 square degrees aboard the SATech-01 satellite of the CAS,

launched on July 27, 2022. The above result is preliminary and the final

result will be published elsewhere.

GCN Circular 32769

Subject
GRB 221009A: continued Assy optical afterglow observations, possible SN evidence
Date
2022-10-16T15:33:29Z (3 years ago)
From
Alexei Pozanenko at IKI, Moscow <apozanen@iki.rssi.ru>
S. Belkin (IKI, HSE), V. Kim (FAI), A. Pozanenko (IKI),  M. Krugov 
(FAI), Y. Aimuratov (FAI), N. Pankov (HSE) report on behalf of GRB IKI FuN:

We continue observations of GRB 221009A (Swift J1913.1+1946) (Dichiara 
et al., GCN 32632; Kennea and Williams, GCN  32635; Veres et al., GCN 
32636; Bissaldi et al., GCN  32636; Svinkin et al., GCN 32641; Piano et 
al., GCN 32657; Pillera et al., GCN 32658;  Gotz et al., GCN 32660; 
Frederiks et al., GCN 32668)  with AZT-20 telescope of Assy-Turgen 
observatory.  The observations were carried out  on 2022-10-11 -- 
2022-10-15. The optical afterglow ( GCNs 32632,  32635, 32636, 32641, 
32657, 32658, 32660, 32666, 32668, 32670, 32671, 32676, 32677, 32678, 
32679, 32680, 32683, 32684, 32685, 32686, 32691, 32692, 32693, 32694, 
32695, 32700, 32705, 32707, 32709, 32727, 32729, 32730, 32736, 32738, 
32739, 32740, 32743, 32746, 32749, 32750; 32752; 32753; 32755; 32758; 
32765).

Preliminary photometry of the afterglow on 2022-10-15 is following

Date       UT start  t-T0       Exp.   Filter  OT    Err.   UL(3sigma)
                     (mid, days)  (s)
2022-10-15 15:29:43  6,10259    30*60  g'      22.60  0.12  23.4
2022-10-15 14:25:00  6,05765    30*60  r'      20.96  0.05  22.9
2022-10-15 14:56:19  6,07939    30*60  i'      20.00  0.04  23.2 
2022-10-15 16:01:07  6,11918    15*60  z'      19.31  0.08  21.0
The photometry is based on the nearby PS1 stars.

The light curve based in our photometry can be found in 
http://grb.rssi.ru/GRB221009A/GRB221009A_lc_cc_7_cut.png

The power law (PL) fit parameters are also shown in the figure and do 
not include photometry on 2022-10-15. It can be seen that the color 
change g-i and photometry g, r on October 15, 2022 deviate significantly 
from the PL approximation. We hypothesize that this behaviour may 
indicate a supernova rise.

GCN Circular 32771

Subject
GRB 221009A: Faulkes Telescope North continued optical afterglow follow-up
Date
2022-10-16T21:35:11Z (3 years ago)
From
Manisha Shrestha at University of Arizona <mshrestha1@arizona.edu>
M. Shrestha (Univ. of Arizona), K. Bostroem (Univ. of Arizona),  D. Sand (Univ. of Arizona), K. D. Alexander (Univ. of Arizona), J. Andrews (Gemini), J. Pearson (Univ. of Arizona), G. Hosseinzadeh (Univ. of Arizona), N. Smith (Univ. of Arizona), D. A. Howell (LCO/UCSB), C. McCully (LCO/UCSB), M. Newsome (LCO/UCSB), E Padilla Gonzalez (LCO/UCSB), C. Pellegrino (LCO/UCSB), G. Terreran (LCO/UCSB), J. Farah (LCO/UCSB) report on behalf of a wider Global Supernova Project collaboration:



We observed the field of Swift GRB 221009A (Dichiara et al. GCN 32632 ) with Faulkes Telescope North, on 2022 October 15 starting at 6:34:12.198 UT (~5.7 days after the trigger) using the MuSCAT3 imager in the r, i, and z bands.  Data were calibrated with respect to nearby PanSTARRS sources for r, i, and z bands .



We clearly detect the optical counterpart in the r, i and z bands and obtain an upper limit on the g band. The magnitudes are as follows:



r  = 21.13 +- 0.06

i  = 20.01 +- 0.05

z = 19.39 +- 0.05



These values are not corrected for galactic extinction and are consistent with the magnitudes reported in Belkin et al. GCN 32769 observed in a similar time frame.

GCN Circular 32780

Subject
GRB 221009A: A type I BdHN of exceptional energetics
Date
2022-10-17T11:16:22Z (3 years ago)
From
Remo Rufinni at ICRA <ruffini@icra.it>
Y. Aimuratov, L. Becerra, C.L. Bianco, C. Cherubini, S. Filippi, M.
Karlica, Liang Li, R. Moradi, F. Rastegar Nia, J.A. Rueda, R. Ruffini, N.
Sahakyan, Y. Wang, S.S. Xue, on behalf of the ICRANet team, report:


GRB221009A detected by Swift (Kennea et al. 2022 GCN32635), Fermi-GBM
(Veres et al. 2022, GCN32636, Lesage et al. 2022, GCN32642), Fermi-LAT
(Bissaldi et al. 2022, GCN32637), with redshift of z=0.151 and an isotropic
equivalent energy of Eiso=2x10^54 erg (de Ugarte Postigo et al. 2022,
GCN32648 and GCN32642) is a typical Binary driven Hypernova of type I
(BdHNI), originating from the collapse of a carbon-oxygen core (CO-core) in
presence of a companion neutron star (NS) with common feature with three
BdHNeI: GRB130427A with "pile up" in the prompt phase (Ruffini et al. 2013,
GCN14526); GRB190114C (Ruffini et al. 2019, GCN23715); and GRB180720B
(Ruffini et al. 2018, GCN23019). As the above three sources, GRB221009A
presents: 1) the optical (Lipunov et al. 2022, GCN32634 and GCN32639;
Perley. 2022 GCN32638; Broens. 2022, GCN32640; Hu et al. 2022, GCN32644;
Mondy: Belkin et al. 2022, GCN32645; de Wet et al.2022, GCN32646; Xu et al.
2022 GCN32647; Odeh 2022, GCN32649; Brivio et al. 2022, GCN32652; Izzo et
al. 2022, GCN32765), radio (Bright et al. 2022, GCN32653 and Farah et al.
2022, GCN32655) and X-ray (Kennea et al, 2022, GCN32635, and GCN32651)
synchrotron afterglow emissions as well as the TeV emission (Yong Huang et
al. 2022, GCN32677), which in BdHNI originate from accreting millisecond
spinning newborn NS (Rueda et al. 2022, e-Print: 2204.00579 [astro-ph.HE]);
2) the ultra-relativistic prompt emission (UPE) phase (Moradi et al. 2021,
PRD 104, 063043 and Rastegarnia et al. 2022, EPJC 82, 778) and GeV emission
(Rueda et al 2022 ApJ 929 56) originated from the black hole formed by
hypercritical accretion of the supernova ejecta on the NS companion; and 3)
the optical emission of the nickel decay of the supernova (SN), created by
the collapse of the CO-core. The first evidence of the supernova rise is
reported by S. Belkin et al. 2022, (GCN32769). In this GRB the bolometric
optical peak of SN is expected to be observed at 15.57+/-2.0 days after the
Fermi-GBM trigger (October 24th 2022, uncertainty from October 22nd 2022 to
October 26th 2022, with the bolometric optical luminosity of
L=(9.45+/-2.8)x10^42 erg/s; Aimuratov et al. in preparation).

GCN Circular 32788

Subject
GRB 221009A: Second epoch of NuSTAR data
Date
2022-10-18T03:28:57Z (3 years ago)
From
Daniel Brethauer at UC Berkeley <daniel_brethauer@berkeley.edu>
Daniel Brethauer (UC Berkeley), Raffaella Margutti (UC Berkeley), Judith
Racusin (NASA/GSFC), Brian Grefenstette (Caltech), Kate D. Alexander
(Arizona), Tom Barclay (NASA/GSFC), Edo Berger (Harvard), Eric Burns (LSU),
Brad Cenko (NASA/GSFC), Yvette Cendes (Harvard), Ryan Chornock (UC
Berkeley), Tarraneh Eftekhari (Northwestern), Jamie Kennea (PSU), Tanmoy
Laskar (Utah)


A second epoch of NuSTAR observations of GRB221009A was obtained on October
15, 2022 starting at 05:21:09 UTC (~5.6 days since trigger; Dichiara et
al., GCN 32632; Veres et al., GCN 32636) with an exposure time of 25 ks
(PIs Racusin and Margutti).


The 3-79 keV spectrum is well fit by a power law with a photon index of
Gamma = 1.91 +/- 0.02 (1 sigma c.l.), which suggests spectrally softer
emission than observed during the first NuSTAR epoch (Brethauer et al., GCN
32695). The inferred NuSTAR power-law index is consistent with the value
inferred from contemporaneous Swift-XRT observations, which indicate Gamma=
1.79 +/- 0.11 and a best-fitting intrinsic absorption NHint=(0.46 +/-
0.10)e22 cm-2 at z=0.151 for an assumed Galactic neutral hydrogen column
density NH_mw=0.563e22 cm-2 (Willingale et al., 2013). The corresponding
unabsorbed flux is ~4.5e-11 ergs/cm^2/s  (3-79 keV), indicating a factor
~10 fading with respect to the previous epoch of NuSTAR data (Brethauer et
al., GCN 32695).


Additional epochs of NuSTAR monitoring are planned on October 20th, and
November 2nd. We thank the entire NuSTAR SOC for promptly implementing
these observations.

GCN Circular 32791

Subject
GRB 221009A: Medicina Radio Telescope observations
Date
2022-10-18T14:16:50Z (3 years ago)
From
Marco Marongiu at Ferrara U <marco.marongiu@unife.it>
M. Marongiu, E. Egron, A. Pellizzoni (INAF/OAC), S. Righini (INAF/IRA), 
C. Guidorzi (UniFe), and S. Mulas (UniCa), report:

We observed GRB 221009A (Dichiara et al. GCN 32632) with the Medicina 
Radio Telescope (www.radiotelescopes.inaf.it) through single-dish 
imaging in X-band (central frequency 8.2 GHz, bandwidth 0.3 GHz) in two 
time intervals: (1) 13:30-19:30 UTC on October 14, 2022 (4.97-5.22 days 
after the burst), and (2) 11:30-19:30 UTC on October 17, 2022 (7.89-8.22 
days after the burst).

In our analysis, at 5.1 days (after the burst) we detected a faint radio 
emission at 8.2 GHz with a flux density of 26 +- 5 mJy at a position 
consistent with the optical position (Dichiara et al., GCN 32632) and 
the radio position (Laskar et al., GCN 32740, Laskar et al., GCN 32757).

We did not detect any significant signal with a 2-sigma upper limit of 
20 mJy at 8.1 days.


We acknowledge the scheduler and the staff of the Medicina Radio 
Telescope for approving and executing these observations.

GCN Circular 32793

Subject
The probability of observing GRB 221009A at z = 0.151
Date
2022-10-18T14:47:32Z (3 years ago)
From
Jean-Luc Atteia at IRAP <jean-luc.atteia@irap.omp.eu>
The prompt emission of the extraordinarily bright GRB 221009A was detected in space by Swift (Dichiara et al. GCNC 32632, Krimm et al. 32688), Fermi (Veres et al. GCNC 32636, Bissaldi et al. GCNC 32637, Lesage et al. GCNC 32642, Pillera et al. GCNC 32658, Omodei et al. GCNC 32760), AGILE (Ursi et al. GCNC 32650, Piano et al. GCNC 32657), INTEGRAL (Gotz et al. GCNC 32660), Solar Orbiter (Xiao et al. GCNC 32661), SRG (Lapshov et al. GCNC 32663), Konus (Frederiks et al. GCNC 32668), GRBAlpha (Ripa 
et al. GCNC 32685), STPSat-6 (Mitchell et al. GCNC 32746), HEBS (Liu et al. GCNC 32751). Various estimates of its prompt isotropic energy ranks it among the most energetic GRBs (Cenko et al. 2011, Atteia et al. 2017):
Gotz et al. GCNC 32660 -���������� Eiso = 8e53 ergs in [75 keV 1 MeV] ;
Frederiks et al. GCNC 32668 - Eiso = 3e54 ergs in [20 keV - 10 MeV ?] ;
Kann et al. GCNC 32762 -���������� Eiso = 6e54 ergs in [0.1 keV - 100 MeV] ;

We discuss here the chance to observe such an energetic GRB at redshift z = 0.151 (de Ugarte Postigo GCNC 32648, Castro-Tirado et al. GCNC 32686), considering the rate of such extremely energetic GRBs observed at higher redshifts.

Considering a flat cosmology with H0 = 67.4 km/s/Mpc and Omegam = 0.315 (Planck Collaboration et al. 2020), we extrapolate the rate of ���4 extremely energetic GRBs per year derived by Atteia et al. (2017) in the redshift range [1,5], to the volume of the nearby universe enclosed within z = 0.151.

- Assuming a constant GRB formation rate, we obtain 1 extremely energetic GRB per ~130 yr.
- Assuming the GRB formation rate of Palmerio & Daigne (2021), we obtain 1 extremely energetic GRB per ~520 yr.

We conclude that there is a ~10% probability to observe an event like GRB 221009A about 50 years after the discovery of the first GRB.

Bibliography :
- Cenko, S. B., Frail, D. A., Harrison, F. A., et al. 2011, ApJ, 732, 29
- Atteia, J.-L., Heussaff, V., Dezalay, J.-P., et al. 2017, ApJ, 837, 119
- Palmerio, J.T. & Daigne, F. 2021, A&A, 649, 166
- Planck Collaboration, Aghanim, N., Akrami, Y., et al. 2020, A&A, 641, A6

GCN Circular 32795

Subject
GRB 221009A: GRANDMA observations
Date
2022-10-18T15:32:46Z (3 years ago)
From
Sarah Antier at OCA <sarah.antier@oca.eu>
Y. Rajabov, T. Sadibekova (UBAI), Y. Tillayev (UBAI, NUUz),
C. Rinner, Z. Benkhaldoun (OUCA), X. F. Wang (THU/BJP),
J. Zhu (BJP), X. Y. Zeng (CGTU), L. T. Wang, A. Iskandar (XAO),
A. M. Fouad, A. Takey A. Shokry, M. Soliman (NRIAG), P. Hello,
T. Hussenot (IJCLAB), M. Boer, A. de Ugarte Postigo, S. Antier (OCA/Artemis)
D. A. Kann (Goethe Univ.), E. Burns (LSU), A. Simon, A. Baransky
(Kyiv Univ), L. Abe, Ph. Bendjoya, J.-P. Rivet (Lagrange-OCA),
D. Vernet (Galilee-OCA), S. Brunier (KNC), R. Inasaridze, R. Natsvlishvili,
N. Kochiashvili (AbAO), S.Beradze, V. Aivazyan, G. Kapanadze, O.Burkhonov,
J. G. Ducoin (IAP), S.Ehgamberdiev (UBAI, NUUz), A. Klotz (OMP/IRAP),
I. Tosta e Melo (INFN-LNS) report on behalf of GRANDMA collaboration:

The GRANDMA telescope network responded to the alert of the ultra-bright
GRB 221009A (Swift detection: Dichiara et al., GCN 32632; Fermi
GBM detection: Veres et al., GCN 32636).

The first observations started 2.30 h after the Fermi/GBM trigger time
with TAROT-TRE without filter.

Below, we report select observations. We also report our 5-sigma upper
limits. Magnitudes are given in the AB system.

T-T0 (day)| MJD���� | Obser.���� |Exposure| Filter | Mag +/- err |Upp.Lim. (AB)
___________________________________________________________________________
1.069 |59862.622720|UBAI-ST| 6x180s |R-Bessel| 18.3�� +/- 0.1 | 19.2
1.136 |59862.689664| KAO���� | 11x100s| sdssr�� | 18.57 +/- 0.05| 20.5
1.134 |59862.687523| KAO���� | 2x120s | sdssg�� | 20.43 +/- 0.2 | 19.8
1.154 |59862.707801| KAO���� | 9x80s�� | sdssi�� | 17.56 +/- 0.05| 20.3
1.166 |59862.719039| KAO���� | 2x120s | sdssz�� | 16.93 +/- 0.05| 19.7
1.223 |59862.776151|Lisnyky| 10x30s |R-Bessel| 18.15 +/- 0.1 | 19.6
1.258 |59862.811817| MOSS�� | 20x60s | clear�� | 18.5�� +/- 0.1 | 20.3
1.301 |59862.854179|C2PU-O | 2x300s | sdssr�� | 18.96 +/- 0.1 | 20
3.027 |59864.580925| SNOVA | 10x150s| clear�� |�������������� -���������� | 19.7
3.047 |59864.600648|UBAI-ST| 5x240s |R-Bessel| 19.85�� +/- 0.1| 19.3
4.191 |59865.743981| KAO���� | 21x110s| sdssz�� | 18.8���� +/- 0.1| 19.7

These detections and limits are consistent with the detections and limits
previously reported in Lipunov et al., GCN 32634; Perley, GCN 32638;
Broens, GCN 32640; Hu et al., GCN 32644; Belkin et al., GCN 32645; GCN 32769
; Wet et al., GCN 32646; Xu et al., GCN 32647; de Ugarte Postigo et al., GCN
32648; Odeh, GCN 32649; GCN 32666; Brivio et al., GCN 32652; Kuin et al.,
GCN 32656; Paek et al., GCN 32659; Kumar et al., GCN 32662; Romanov, GCN
32664; 32679; Chen et al., GCN 32667; Vidal et al., GCN 32669; Kim et al.,
GCN 32670; Groot et al., GCN 32678; Castro-Tirado et al., GCN 32686;
Watson et al., GCN 32692; Strausbaugh et al. GCN 32693; Butler et al., GCN
32705; Vinko et al., GCN 32709; Mao et al., GCN 32727; Zaznobin et al.,
GCN 32729; Sasada et al., GCN 32730; Strausbaugh & Cucchiara, GCN 32738;
O'Connor et al., GCN 32739; GCN 32750; Bikmaev et al., GCN 32743; GCN
32752; Rastinejad & Fong, GCN 32749; Schneider et al., GCN 32753;
D���Avanzo et al., GCN 32755; Huber et al., GCN 32758; Shrestha et al.,
GCN 32759; 32771; Izzo et al., GCN 32765.

The observations were contaminated by the nearly full Moon.

Further analysis are ongoing in GRANDMA especially on
TAROT, ShAO-T60, AbAO-T70 and C2PU-O.

The KAO, UBAI-ST have been calibrated using nearby
stars from the Pan-STARRS catalog in sdss r, g, i and z, measured with
STDpipe (Karpov 2022). Lisnyky-AZT has been calibrated using field
stars from the PanSTARRS-DR1 catalog, measured with the MUPHOTEN pipeline
(Duverne et al. 2022). MOSS and SNOVA data have been calibrated with
Gaia DR2.

We advocate a joint multi-wavelength publication for this event and we are
happy to collaborate with teams that have the same spirit,
to be able to explore the best astrophysical scenario.

GRANDMA is a worldwide telescope network (grandma.ijclab.in2p3.fr)
devoted to the observation of transients in the context of multi-messenger
astrophysics (Antier et al. 2020 MNRAS 497, 5518). Kilonova-Catcher (KNC) is
the citizen science program of GRANDMA (http://kilonovacatcher.in2p3.fr/).

GCN Circular 32799

Subject
GRB 221009A: Continued LDT Afterglow Monitoring
Date
2022-10-19T03:59:58Z (3 years ago)
From
Brendan O'Connor at UMD <oconnorb@umd.edu>
B. O'Connor (UMD/GWU), S. B. Cenko (NASA/GSFC), E. Troja (UTV/ASU),
S. Dichiara (PSU), A. Kutyrev (NASA/GSFC), S. Veilleux (UMD),
J. Durbak (UMD), on behalf of a larger collaboration:

We performed target of opportunity observations of GRB 221009A
(Dichiara et al., GCN 32632, Veres et al., GCN 32636)
with the 4.3m Lowell Discovery Telescope (LDT) in Happy Jack, AZ.
Observations began on October 13, 2022 at 02:05:29 UT corresponding
to ~9.5 d after the GRB. We obtained images in the riz filters at
an airmass ~1.1 with seeing ~1.7".

The afterglow is clearly detected in each filter. We obtain the
following magnitudes calibrated against the PS1 catalog:

r = 21.68 +/- 0.07 AB mag
i = 20.72 +/- 0.05 AB mag

These magnitudes are not corrected for Galactic extinction.

We thank the staff of the Lowell Observatory for assistance
with these observations.

GCN Circular 32800

Subject
GRB 221009A: Spectroscopic detection of emerging SN features
Date
2022-10-19T11:23:30Z (3 years ago)
From
Antonio de Ugarte Postigo at OCA <deugarte@oca.eu>
A. de Ugarte Postigo (OCA), L. Izzo (DARK/NBI), C. C. Thoene
 (ASU-CAS), J. P. U. Fynbo (DAWN/NBI), D. A. Kann (Goethe Univ.), 
J. F. Agui Fernandez (IAA-CSIC), N. R. Tanvir (Leicester Univ.) report:

We have been spectroscopically monitoring the evolution of the 
extremely bright GRB 221009A (Swift detection: Dichiara et al., 
GCN 32632; Fermi GBM detection: Veres et al., GCN 32636) using 
OSIRIS at the 10.4m GTC telescope. In a spectrum combining data 
taken on 16 and 17 October (at an average time of ~8 days after the 
burst), covering the spectral range between 3700 and 10000 AA, the 
emission is still clearly dominated by the afterglow. However, after 
subtracting a model of the continuum, the spectrum shows undulations 
characteristic of a GRB-SN. In particular we identify broad features at 
similar wavelengths (after correcting for the redshift difference) as 
those present in SN 1998bw, with somewhat larger velocities. This is 
indicative of the emergence of the associated supernova. Further 
follow-up observations are planned.

GCN Circular 32802

Subject
GRB 221009A X-ray light-curve and the indication of TeV light-curve
Date
2022-10-19T15:28:45Z (3 years ago)
From
Remo Rufinni at ICRA <ruffini@icra.it>
Y. Aimuratov, L. Becerra, C.L. Bianco, C. Cherubini, S. Filippi, M.
Karlica, Liang Li, R. Moradi, F. Rastegar Nia, J.A. Rueda, R. Ruffini, N.
Sahakyan, Y. Wang, S.S. Xue, on behalf of the ICRANet team, report:

LHAASO observed more than 5000 very high energy (VHE) photons in GRB
221009A, with the highest energy reaching 18 TeV (GCN 32677). Previously,
high energy TeV emissions were also observed in GRB 180720B (Abdalla et al.
2019), 190114C (MAGIC Collaboration 2019), 190829A (H.E.S.S. Collaboration
2021) and 201216C (Blanch et al. GCN 29075). A common feature of these
bursts is that the TeV light-curve follows a power-law decay with a similar
index as the X-ray light-curve, and the TeV luminosity is tens of percent
of the X-ray luminosity (see attached figure 1 and the references of
Abdalla et al. 2019, MAGIC Collaboration 2019 and H.E.S.S. Collaboration
2021, Ruffini et al. 2021, Rueda et al. 2022, Rastegarnia et al. 2022, Wang
et al. 2022). Here we present the X-ray light-curve of GRB 221009A observed
by Swift-XRT (GCN 32651), and the t0 is taken from the Fermi-GBM trigger
time (GCN 32636), see attached figure 2, a power-law of index -1.58 is
fitted. The shadow region shows 20%-60% of the X-ray luminosity, which is
expected to be the 0.3-1 TeV luminosity (17% less luminous for 0.5-18 TeV
assuming a power-law spectrum of photon index -2) of this new burst if it
shares the same behavior as the previous ones. We encourage further
observations, especially the VHE observations, because this burst probably
is more luminous than the previous ones, and it will be precious to have a
late time (after days) VHE luminosity which was never achieved before, as
well as the optical observations for the supernova appearance (GCN 32670,
GCN 32780).

Figure 1: http://www.icranet.org/docs/fig1.png
Figure 2: http://www.icranet.org/docs/fig2.png



http://www.icranet.org

http://www.icranet.org

GCN Circular 32803

Subject
GRB 221009A: BOAO NIR detections
Date
2022-10-19T15:52:11Z (3 years ago)
From
Myungshin Im at Seoul Nat U <mim@astro.snu.ac.kr>
Myungshin Im, Gregory S.-H. Paek, Gu Lim, Hyeonho Choi, Sophia Kim (SNU),
Hyun-Il Sung (KASI), Yuji Urata (NCU) on behalf of a larger collaboration

We observed the field of GRB 221009A (Swift detection: Dichiara et al., GCN
32632; Fermi GBM detection: Veres et al., GCN 32636), in J and K filters
with the KASINICS instrument on the 1.8 m telescope of the Bohyunsan
Optical Astronomy Observatory (BOAO), Korea. The observation started at
2022-10-18-11:34 (UT) or JD=2459870.98230324, taking a series of images for
about 1.25 hrs.

We identify the afterglow in the KASINICS images, with a rough photometry
of K ~ 18.6 AB mag. Further observations and analysis are being carried out
to obtain more data and refine the photometry.

We thank the staff of BOAO for carrying out the observation.

GCN Circular 32804

Subject
GRB 221009A: TNG NIR detection
Date
2022-10-19T16:28:04Z (3 years ago)
From
Paolo D'Avanzo at INAF-OAB <pda.davanzo@gmail.com>
M. Ferro, R. Brivio, P. D���Avanzo (INAF-OAB), S. Piranomonte (INAF-OAR), V. Lorenzi, G. Mainella (INAF-TNG), 
on behalf of the CIBO collaboration report:

We observed the field of GRB 221009A (Dichiara et al., GCN 32632; Kennea & Williams, GCN 32635; Veres et al., 
GCN 32636; Bissaldi et al., GCN 32637; Svinkin et al., GCN 32641; Ursi et al., GCN Circ. 32650) with the Italian 3.6m 
TNG telescope equipped with the near-infrared camera NICS. A series of images were obtained with the J, H and K filters 
on 2022-01-16 at a mid time of about 7.3 days after the GBM trigger time. 

The NIR afterglow (Brivio et al., GCN Circ. 32652) is clearly detected in all bands. From preliminary photometry we derive 
the following magnitude:

H = 16.45 +/- 0.04

(Vega; calibrated against the 2MASS catalogue).


We acknowledge the TNG visiting astronomers B. Lakeland and B. Nicholson for their support.

GCN Circular 32805

Subject
Improved IPN localization for GRB 221009A (BepiColombo-MGNS light curve)
Date
2022-10-19T16:43:28Z (3 years ago)
From
Dmitry Svinkin at Ioffe Institute <svinkin@mail.ioffe.ru>
A.S. Kozyrev, D.V. Golovin, M.L. Litvak, I.G. Mitrofanov, and A.B. Sanin
on behalf of the MGNS/BepiColombo team,

J. Benkhoff on behalf of the BepiColombo team,

D. Svinkin, D. Frederiks, A. Ridnaia, A. Lysenko,
and T. Cline on behalf of the Konus-Wind team,

A. Goldstein, M. S. Briggs, C. Wilson-Hodge,
and E. Burns on behalf of the Fermi GBM team,

E. Bozzo and C. Ferrigno, on behalf of the INTEGRAL SPI-ACS GRB team,

and

S. Barthelmy, J. Cummings, H. Krimm, D. Palmer, and A. Tohuvavohu
on behalf of the Swift-BAT team, report:

The extremely bright, long-duration GRB 221009A
(GCNs 32632, 32635, 32636, 32637, 32641, 32642, 32650, 32657,
32658, 32668, 32685, 32751; ATels 15650, 15656, 15660)
was detected by the MGNS/BepiColombo interplanetary gamma-ray detector. 
The burst light curves in the energy range 280-460 keV exhibit a 
multi-peaked pulse structure with a total duration of ~6.6 min. The 
source of GRB 221009A was obscured for MGNS by spacecraft structure that 
have limited transparency in the specified above energy range.

The link below provides a plot of the time profile of the gamma-ray 
count rate. The GRB221009A.TXT file, also available at this link,
contains light curve data in three columns: time in UTC, accumulated 
count and accumulation time.

http://l503.iki.rssi.ru/owncloud/index.php/s/HZtqdQ1b9QW3ojv

Using the BepiColombo (MGNS) data we have triangulated GRB 221009A
to the 3 sigma error box whose coordinates are:
---------------------------------------------
   RA(2000), deg                 Dec(2000), deg
  ---------------------------------------------
  Center:
   287.761 (19h 11m 03s) +20.670 (+20d 40' 11")
  Corners:
   283.599 (18h 54m 24s) +27.415 (+27d 24' 54")
   283.634 (18h 54m 32s) +28.133 (+28d 08' 00")
   291.780 (19h 27m 07s) +12.770 (+12d 46' 14")
   291.767 (19h 27m 04s) +11.822 (+11d 49' 20")
  ---------------------------------------------
The error box area is 6.63 sq. deg, and its maximum
dimension is 18 deg (the minimum one is 23 arcmin).
The Sun distance was 92 deg.

This box may be further improved.

The Swift-XRT source (GCN 32632) is inside the box.
The distance between the source and
the Konus-MGNS annulus center line is 1.7 arcmin.

An updated triangulation map and HEALPix FITS file are posted at
http://www.ioffe.ru/LEA/GRBs/GRB221009_T47819/IPN/

GCN Circular 32808

Subject
GRB 221009A: Peak luminosity of the supernova vs. synchrotron afterglow
Date
2022-10-20T14:57:47Z (3 years ago)
From
Remo Rufinni at ICRA <ruffini@icra.it>
Y. Aimuratov, L. Becerra, C.L. Bianco, C. Cherubini, S. Filippi, M.
Karlica, Liang Li, R. Moradi, F. Rastegar Nia, J.A. Rueda, R. Ruffini, N.
Sahakyan, Y. Wang, S.S. Xue, on behalf of the ICRANet team, report:

GRB 221009A appears to be a rare example (Jean-Luc Atteia et al. 2022, GCN
32793) of a particularly energetic and close GRB (de Ugarte Postigo et al.
2022, GCN 32648 and Lesage et al. 2022, GCN 32642 and N.P.M. Kuin et al.
2022, GCN 32656). Within the BdHN model, we have followed the X-ray,
optical, and radio afterglows originating from synchrotron emission powered
by fast spinning newborn neutron stars (vNS) with initial periods of
fraction of a millisecond, accreting the supernova ejecta, created by the
collapse of a carbon-oxygen core (Rueda et al. 2022, arXiv:2204.00579).
Figures 1, 2 and 3 show the afterglows of three type I BdHNe, namely GRB
180720B (Ruffini et al. 2018, GCN 23019), GRB 190114C (Ruffini et al. 2019,
GCN 23715), and GRB 211023A (Aimuratov et al. 2021, GCN 31056), and the
prediction of their associated supernova.
We have indicated the expected time of the occurrence of the supernova in
GRB 221009A (Aimuratov et al. 2022, GCN 32780). The ongoing observations in
optical, radio, and X-ray bands are strongly recommended for allowing the
determination of the spin and magnetic field of the vNS. This will probe as
well if the optical synchrotron emission, at ~ 10^6 s from the Fermi-GBM
trigger, impedes the observations of the optical emission of the supernova
originating from nickel decay (Aimuratov et al. in preparation, see also
data from Ilfan Bikmaev et al. 2022, GCN 32752, and Jia. Ren et al. 2022,
arXiv:2210.10673, reproduced in Fig. 4).

Fig1: http://www.icranet.org/docs/Fig1.pdf
Fig2: http://www.icranet.org/docs/Fig2.pdf
Fig3: http://www.icranet.org/docs/Fig3.pdf
Fig4: http://www.icranet.org/docs/Fig4.pdf

GCN Circular 32809

Subject
GRB221009A: LBT optical imaging
Date
2022-10-20T15:24:03Z (3 years ago)
From
Andrea Rossi at INAF <andrea.rossi@inaf.it>
A. Rossi, E. Maiorano (INAF-OAS), D. B. Malesani (Radboud Univ. and 
DAWN/NBI)on behalf of the CIBO collaboration, F. Cusano (INAF-OAS),��and 
D. Paris (INAF-OA Roma), report:

We observed the field of GRB 221009A (Dichiara et al., GCN 32632; Kennea 
& Williams, GCN 32635; Veres et al.,��GCN 32636; Bissaldi et al., GCN 
32637; Svinkin et al., GCN 32641; Ursi et al., GCN Circ. 32650) 
simultaneously in the blue and red arms with the g'+r' and g'+i'��bands 
with the MODS instrument mounted on LBT (Mt Graham, AZ, USA). We 
observed for 22 min per arm at the midtime 03:11 UT on 2022-10-18, 8.58 
days after the burst trigger. Observations were performed under modest 
weather conditions with an average seeing of ~1" but high humidity and 
passing cirrus.

We clearly detect the afterglow and we preliminary measure

r=21.63+-0.02 (AB system),

calibrated against Pan-STARRS field stars.

We acknowledge the excellent support from the LBTO and LBT-INAF staff, 
particularly A. Becker and D. G. Huerta in obtaining these observations.

GCN Circular 32811

Subject
GRB 221009A: 1.3m DFOT Optical Observations
Date
2022-10-21T07:11:24Z (3 years ago)
From
Rahul Gupta at ARIES, India <rahulbhu.c157@gmail.com>
Rahul Gupta, Amit Kumar Ror, S. B. Pandey, A. Aryan, A. Ghosh, Dimple, and
K. Misra (ARIES) report as a part of a larger international collaboration:


We performed target of opportunity observations of the extremely bright GRB
221009A (Dichiara et al., GCN 32632; Kennea and Williams, GCN 32635; Veres
et al., GCN 32636; Bissaldi et al., GCN 32637; Svinkin et al., GCN 32641; Ursi
et al., GCN 32650; Piano et al., GCN 32657; Pillera et al., GCN 32658; Gotz
et al., GCN 32660; Xiao et al., GCN 32661; Frederiks et al., GCN 32668; Ripa
et al., GCN 32685) using the 2Kx2K CCD Imager mounted at the 1.3m Devasthal
Fast Optical Telescope (DFOT) located at the Devasthal observatory of
Aryabhatta Research Institute of Observational Sciences (ARIES), India. The
observations were started on 2022-10-16 at 14:41:41 UT, i.e., ~ 7.06 days
after the detection. We have taken multiple frames in the R filter at
different epochs. We clearly detected the optical afterglow of GRB
221009A (GCNs
32632, 32635, 32636, 32641, 32657, 32658, 32660, 32666, 32668, 32670,
32671, 32676, 32677, 32678, 32679, 32680, 32683, 32684, 32685, 32686,
32691, 32692, 32693, 32694, 32695, 32700, 32705, 32707, 32709, 32727,
32729, 32730, 32736, 32738, 32739, 32740, 32743, 32746, 32749, 32750;
32752; 32753; 32755; 32758; 32765; 32769; 32771; 32795; 32799; 32800;
32803; 32804; 32809) in our stacked image. The preliminary photometric
estimate of the afterglow is the following :

Date Start UT   T-T0 (mid, days) Filter  Exp time (sec)   Magnitude

=========================================================
2022-10-16 14:41:41   ~7.09       R           200*25          21.30 +/- 0.04


Further follow-up observations are planned. The magnitude is not corrected
for the Galactic extinction in the direction of the burst. Photometric
calibration is performed using the standard stars from the USNO-B1.0
catalog.

This circular may be cited.

GCN Circular 32818

Subject
GRB 221009A: optical observations, SN photometric evidence
Date
2022-10-22T22:47:16Z (3 years ago)
From
Alexei Pozanenko at IKI, Moscow <apozanen@iki.rssi.ru>
S. Belkin (IKI, HSE), A. Moskvitin (SAO RAS), V. Kim (FAI), A. Pozanenko 
(IKI),  M. Krugov (FAI), R. Uklein (SAO RAS), N. Pankov (HSE) report on 
behalf of GRB IKI FuN:

We continue observations of GRB 221009A (Swift J1913.1+1946) (Dichiara 
et al., GCN 32632; Kennea and Williams, GCN  32635; Veres et al., GCN 
32636; Bissaldi et al., GCN  32636; Svinkin et al., GCN 32641; Piano et 
al., GCN 32657; Pillera et al., GCN 32658;  Gotz et al., GCN 32660; Xiao 
et al., GCN 32661; Frederiks et al., GCN 32668; GCN 32668; Ripa
et al., GCN 32685; Kozyrev et al., GCN 32805).  Observations  with 
AZT-20 telescope of Assy-Turgen observatory obtained on  October 20, 21 
and TOO photometry with BTA SAO RAS telescope equipped with SCORPIO-2 
was obtained on  October 16 and 18.  The optical afterglow (GCNs 32632, 
  32635, 32636, 32641, 32657, 32658, 32660, 32666, 32668, 32670, 32671, 
32676, 32677, 32678, 32679, 32680, 32683, 32684, 32685, 32686, 32691, 
32692, 32693, 32694, 32695, 32700, 32705, 32707, 32709, 32727, 32729, 
32730, 32736, 32738, 32739, 32740, 32743, 32746, 32749, 32750; 32752; 
32753; 32755; 32758; 32765; 32769; 32771; 32795; 32799; 32803; 32804; 
32809; 32811) is detected in combined images of g',r',i' filters.

Preliminary photometry of the afterglow on 2022-10-20/21 obtained in 
Assy observatory with  AZT-20 telescope is following

Date       UT start  t-T0       Exp.   Filter  OT    Err.   UL(3sigma)
                     (mid, days)  (s)           (AB)
2022-10-20/21 n/d   11.55024    59*60  g'      23.7   0.2   24.5
2022-10-21 14:18:18 12.05299    30*60  r'      21.94  0.07  23.9
2022-10-21 14:49:37 12.08516    30*60  i'      20.72  0.11  23.3

The photometry is based on nearby PS1 stars.

The light curve based on our observations can be found in 
http://grb.rssi.ru/GRB221009A/GRB221009A_lc_cc_15_cut.png

We observe a bump in the light curve starting on 6th days since trigger. 
The light curve is clearly chromatic at the bump. We  can assume that 
the chromatic bump is a supernova over an afterglow of GRB 221009A 
(Belkin et al., GCN 32769).

GCN Circular 32819

Subject
GRB 221009A: Analysis of the initial episode using data of GBM/Fermi and SPI-ACS/INTEGRAL
Date
2022-10-22T23:05:12Z (3 years ago)
From
Alexei Pozanenko at IKI, Moscow <apozanen@iki.rssi.ru>
P. Minaev (IKI), A. Pozanenko (IKI), I. Chelovekov (IKI) report on 
behalf of GRB IKI FuN:

We analyze the first episode of GRB 221009A (Dichiara et al., GCN 32632; 
Kennea and Williams, GCN  32635; Veres et al., GCN 32636; Bissaldi et 
al., GCN  32636; Svinkin et al., GCN 32641; Piano et al., GCN 32657; 
Pillera et al., GCN 32658;  Gotz et al., GCN 32660; Xiao et al., GCN 
32661; Frederiks et al., GCN 32668; GCN 32668; Ripa et al., GCN 32685; 
Kozyrev et al., GCN 32805) not affected by dead time and pile-up 
instrumental effects, using publicly available data of GBM/Fermi and 
SPI-ACS/INTEGRAL.

We investigate energy spectrum of the time interval (T0-1, T0+55) s, 
where T0 = 13:16:59 UTC 2022-10-09 is a time of  GBM/Fermi trigger.  The 
spectrum can be fitted by a simple power law model with the spectral 
index of gamma = -1.68 +/- 0.01.

See the spectrum in http://grb.rssi.ru/GRB221009A/GRB221009A_1st_episode.png

It is in a contradiction with CPL (power law with exponential cutoff) 
spectral model for the episode, obtained by Lesage et al., GCN 32642 
using GBM/Fermi data (Epeak = 375 +/- 87 keV) and by Frederiks et al., 
GCN 32668 using Konus/WIND data (Epeak = 975 (-332, +712) keV). The 
value of spectral index is not typical for indexes before the break (in 
CPL or Band model), but it is a rather typical for the index after the 
break in Band model. We hypothesize the actual break to be placed at low 
energies (Epeak < 20 keV). The hypothesis could be supported by placing 
Eiso parameter into Amati correlation diagram.   The Eiso = (3.2 +/- 
0.1)E51 erg is calculated  within our power law model with gamma = -1.68 
and using redshift value of z = 0.151 (de Ugarte Postigo et al., GCN 
32648; Castro-Tirado et al., GCN 32686). The Eiso value corresponds to 2 
sigma range of possible Epeak value of (20, 315) keV for type II (long) 
GRBs (Minaev et al., MNRAS, 492, 2, 1919, 2020).

See the correlation diagram in
http://grb.rssi.ru/GRB221009A/GRB221009_Amati_1st_episode.png

The softness of the spectrum is also confirmed by our analysis of 
SPI-ACS/INTEGRAL data: assuming high values of Epeak (e.g. Epeak = 975 
keV) and using SPI-ACS - GBM cross-calibration method to convert SPI-ACS 
count fluxes to energy units (Minaev et al., in preparation) we obtain 
underestimated value of fluence F_ACS = (1.3 +/- 0.3)E-5 erg/cm^2  for 
Epeak = 975 keV, which is less than reference value of F_GBM = (2.38 +/- 
0.04)E-5 erg/cm^2 in (10, 1000) keV range, calculated within our power 
law model with gamma = -1.68.
Using data of GBM/Fermi we perform cross-correlation analysis of the 
initial episode and find significant spectral lags, typical for type II 
(long) GRBs (e.g. Minaev et al., Astronomy Letters, 40, 5, 235, 2014). 
Spectral lag ��� energy dependence is fitted satisfactory by logarithmic 
function lag ~ A*log(E) with spectral lag index A = 0.11 +/- 0.03.

The spectral lag and its parameter can be found in 
http://grb.rssi.ru/GRB221009A/GRB221009_GBM_lags_1st_episode.png

GCN Circular 32821

Subject
GRB 221009A: James Webb Space Telescope Observations
Date
2022-10-22T23:17:34Z (3 years ago)
From
Andrew Levan at U.of Leicester <a.levan@astro.ru.nl>
A.J. Levan (Radboud Univ.), T. Barclay (NASA/GSFC), E. Burns (LSU), S. B. Cenko (NASA/GSFC), A. A. Chrimes (Radboud Univ.), P. D���Avanzo (INAF/OABr), V. D���Elia (INAF/OAR and ASI/SSDC), M. Della Valle (INAF/OAC), A. de Ugarte Postigo (Obs. Cote d���Azur), W. Fong (Northwestern), A. S. Fruchter (STScI), B. P. Gompertz (Birmingham), C. L. Hedges (NASA/GSFC), K. E. Heintz (DAWN/NBI), L. Izzo (DARK/NBI), D. A. Kann (Goethe Univ.), J. A. Kennea (PSU), E. Le Floc���h (CEA Paris-Saclay), D. B. Malesani (Radboud Univ. and DAWN/NBI), A. Melandri (INAF/OAR), B. D. Metzger (Columbia and Flatiron/CCA), S. E. Mullally (STScI), S. Piranomonte (INAF/OAR), M. E. Ravasio (Radboud Univ and INAF/OABr), J. L. Racusin (NASA/GSFC), J. C. Rastinejad (Northwestern), R. Salvaterra (INAF/IASF Milan), B. Sbarufatti (INAF/OABr), B. Schneider (CEA Paris-Saclay), R. L. C. Starling (U. Leicester), N. R. Tanvir (U. Leicester), C. C. Thoene (ASU-CAS), R. A. M. J. Wijers (Amsterdam), D. Xu (NAOC) report:

We observed the afterglow of GRB 221009A (Dichiara et al., GCN 32632; Kennea & Williams, GCN 32635; Bissaldi et al., GCN 32637; Veres et al., GCN 32636) with the James Webb Space Telescope on 22 October 2022, approximately 13 days after the Fermi/GBM trigger. Observations were obtained with the NIRSpec prism, spanning the range 0.6-5.3 microns at low resolution (exposure time 1803 s starting at 13:50 UT), and with MIRI using the Low Resolution Spectroscopy mode, spanning the range 5-12 microns (exposure time 555 s starting at 14:51 UT).

The optical/IR counterpart is well detected in both acquisition and spectral series, providing high signal to noise across the window. Based on provisional NIRSpec data the afterglow appears to be reasonably well described by an absorbed power-law (MW absorption, A_V = 4.2 mag), with a relatively blue spectral slope (nu^-0.4), although we caution that the uncertainty in foreground absorption and photometric calibration means strong statements cannot be made at this stage. 

Further analysis is ongoing. 

We thank the staff of STScI for the rapid assessment of our DDT proposal (GO 2782, PI Levan) and in particular Alison Vick, Greg Sloan and Patrick Ogle for their work to get the observations rapidly into the schedule.

GCN Circular 32828

Subject
GRB 221009A: Determination of the black holes mass and spin
Date
2022-10-24T15:43:08Z (3 years ago)
From
Remo Rufinni at ICRA <ruffini@icra.it>
Y. Aimuratov, L. Becerra, C.L. Bianco, C. Cherubini, S. Filippi, M.
Karlica, Liang Li, R. Moradi, F. Rastegar Nia, J.A. Rueda, R. Ruffini, N.
Sahakyan, Y. Wang, S.S. Xue, on behalf of the ICRANet team, report:

In GRB 221009A, as in GRB 130427A (Ackermann et al. 2014, Science, 343, 42;
and Ruffini et al. 2019, ApJ, 886, 82), the Fermi-GBM data in the prompt
phase are piled up (Lesage et al. 2022, GCN 32642). In both cases there are
missing the ultra-relativistic prompt emission (UPE) phases originating
from quantum electrodynamical process around a Kerr BH (Ruffini et al.
2019, ApJ, 886, 82; and Rueda et al. 2022, ApJ, 929, 56), which were well
observed in GRB 190114C (Moradi et al. 2021, Phys Rev D 104, 063043) and
GRB 180720B (Rastegarnia et al. 2022, EPJC 82, 77). Under these conditions,
for GRB 130427A the 0.1-100 GeV data of Fermi-LAT had allowed to determine
only the lower limit on the BH mass, M>2.31 solar masses, and the upper
limit of its spin parameter, ��<0.4 (Ruffini et al. 2019, ApJ, 886, 82). For
the BDHNI GRB 190114C (Ruffini et al. 2019, GCN 23715), the values of the
BH mass and spin had been determined by taking into account the UPE
contribution: M=4.53 solar masses, ��=0.54 (Moradi et al. 2021, Phys Rev D
104, 063043). The analysis of GRB 130427A applied to GRB 221009A gives for
the BH mass and spin parameters: M>2.36 solar masses and ��<0.5.

We identify the spike at 500s as the X-ray flare (see e.g. Ruffini et al.
2021 MNRAS 504, 5301���5326 for similar GRBs). We also identify the trigger
in the 10 keV-10 MeV data of Fermi-GBM as the dawn of the supernova
(SN-rise), associated with the gravitational collapse of the progenitor
CO-core. The SN ejecta, accreting on the binary NS companion, give origin
to the BH (BH rise, Rueda & Ruffini 2012, ApJL, 758, L7) and accreting on
the vNS they originate the afterglow (vNS rise, Ruffini et al. 2018, ApJ,
869.101; Becerra, et al. 2022, Phys Rev D 106, 083002).

Additional data analysis from AGILE (GCN 32650), Fermi (GCN 32636, 32637,
32642, 32819), Swift (GCN 32635), LHAASO (GCN 32677), HXMT (Atel 15660) are
needed to relate the SN-rise to the first appearance of the vNS (the
vNS-rise) by the TeV radiation (GCN 32780, 32820, 32808), and also to
relate the appearance of the BH (BH-rise) to the identification of the
first GeV emission.

GCN Circular 32850

Subject
GRB 221009A: spectroscopic confirmation of SN in LBT spectra
Date
2022-10-25T16:50:09Z (3 years ago)
From
Andrea Rossi at INAF <andrea.rossi@inaf.it>
E. Maiorano, E. Palazzi, A. Rossi (INAF-OAS), V. D'Elia (SSDC & 
INAF-OAR), and A. Melandri (INAF-OAR) on behalf of the CIBO 
collaboration, and F. Cusano (INAF-OAS), L. Izzo (DARK/NBI) report:

We report the results of the spectroscopic follow-up observations of the 
afterglow of GRB 221009A (Dichiara et al., GCN 32632; Fermi GBM 
detection: Veres et al., GCN 32636). The optical spectra were obtained 
with the Multi-Object Double Spectrographs (MODS) instrument mounted on 
the 2x8.4-m LBT telescope (Mt. Graham, AZ, USA) at 3 UT on 2022-10-18, 
8.56 days after the burst trigger. The spectra cover the wavelength 
range 3200-10000 AA, and we obtained a total of 6 exposures of 900 s.

After correction for the foreground Galactic extinction (E(B-V)=1.324, 
Schlafly & Finkbeiner 2011), we find that the resulting spectrum is 
clearly dominated by the afterglow. We subtracted the afterglow 
contribution assuming a spectral slope -0.7 (using the convention F_nu ~ 
nu^-beta), anchored to the simultaneous NIR flux. This value has been 
obtained modeling the NIR light curve of the afterglow (Ferro et al., 
GCN 32804; D'Avanzo et al., GCN 32755). The remaining low S/N spectrum 
shows features typical of type Ic-BL supernovae. Therefore, we confirm 
the emerging contribution of SN 2022xiw (de Ugarte Postigo et al. et al. 
TNSCR, 2022-3047) as reported by de Ugarte Postigo et al. (GCN 32800).

We acknowledge the excellent support from the LBTO and LBT-INAF staff, 
particularly A. Becker and D. G. Huerta, in obtaining these observations.

GCN Circular 32852

Subject
GRB 221009A: SARA-RM 1m Optical Afterglow Detection
Date
2022-10-26T03:04:37Z (3 years ago)
From
Kyle Pellegrin at Clemson University <pelleg2@g.clemson.edu>
K. Pellegrin, K. Rumstay, and D. Hartmann report:


We observed the field of GRB 221009A detected by Swift(Kennea & Williams,
GCN 32635; Veres et al., GCN 32636) Swift BAT (Dichiara et al., GCN 32632),
Fermi LAT (Bissaldi, GCN 32637), Liverpool Telescope (Perley, GCN 32638),
Vereniging Voor Sterrenkunde (Broens, GCN 32640), IPN (Svinkin, GCN 32641),
BOOTES-2/TELMA (Hu et al., GCN 32644), Mondy (Belkin, GCN 32645), MeerLICHT
(Wet et al., GCN 32646), Nanshan/NEXT (Xu et al., GCN 32647), ESO X-shooter
(de Ugarte Postigo, GCN 32648), Al Khatim Observatory M44 (Odeh, GCN 32649
& GCN 32666), AGILE/MCAL (Ursi et al, GCN 32650), REM (Brivio et al., GCN
32652), AMI-LA (Bright et al., GCN 32653), SAAO (Durbak et al., GCN 32654),
ATA (Farah et al., GCN 32655), Swift UVOT (Kuin and Dichiara, GCN 32656),
AGILE/GRID (Piano et al., GCN 32657), LOAO (Paek et al., GCN 32659),
INTEGRAL SPI/ACS (Gotz et al., GCN 32660), GIT (Kumar et al., GCN 32662),
Burke-Gaffney Observatory (Romanov, GCN 32664), SLT-40cm (Chen et al., GCN
32667), Lick/Nickel Telescope (Vidal et al., GCN 32669), Assy (Kim et al.,
GCN 32670 & Belkin et al., GCN 32769), Global MASTER-Net (Lipunov et al.
GCN 32672 & GCN 32673), BlackGEM (Groot et al., GCN 32678), iTelescope
(Romanov, GCN 32679), Sintez-Newton/ CrAO (Belkin et al., GCN 32684),
COATLI (Watson et al. GCN 32692), LCOGT (Strausbaugh et al., GCN 32693 &
GCN 32738), COATLI (Butler et al., GCN 32705), Konkoly Observatory (Vinko
et al., GCN 32709), GMG (Mao et al., GCN 32727), Sayan Observatory
(Zaznobin et al., GCN 32729), MITSuME Okayama (Sasada et al., GCN 32730),
Lowell Discovery Telescope (O���Connor et al., GCN 32739 & GCN 32799),
RTT-150 (Bikmaev et al., GCN 32743 & GCN 32752), Gemini-South (Rastinejab
and Fong, GCN 32749), Gemini-South (O���Connor et al., GCN 32750), OHP
(Schneider et al., GCN 32753), REM (D���Avanzo et al., GCN 32755), Pan-STARRS
(Huber et al., GCN 32758), Large Binocular Telescope (Shrestha et al., GCN
32759), Faulkes Telescope North (Shrestha et al., GCN 32771), GRANDMA
(Rajabov et al., GCN 32795), BOAO (Im et al., GCN 32803), TNG (Ferro et
al., GCN 32804), LBT (Rossi et al., GCN 32809), DFOT (Gupta et al., GCN
32811), AZT-20 (Belkin et al., GCN 32818), and James Webb (Levan et al.,
GCN 32821) using the SARA 1m optical telescope located at the Roque de los
Muchachos Observatory on La Palma, Canary Islands, Spain, equipped with the
Andor Ikon-L camera.



Observations started at 20:50:13 UTC on 2022-10-23 and ended at 22:29:27
UTC on 2022-10-23. We obtained a series of 90 images with an exposure time
of 60s each in the Johnson-Cousins R filter. The afterglow is faintly seen
after stacking all 90 images together. Photometry on the stacked image
found the afterglow to be R=22.19 +/= 0.07 mag at 14.90190 days (midpoint
of stacked observations) after the Swift trigger (GCN 32632).



Photometry based on the PanSTARRS catalog.



The Southeastern Association for Research in Astronomy (SARA) consortium

operates three telescopes: the 0.9-m SARA-KP at Kitt Peak in Arizona,

the 0.6-m SARA-CT at Cerro Tololo in Chile, and the 1.0-m SARA-RM (formerly

the JKT) telescope at Roque de los Muchachos Observatory in the Canary

Islands. For more information see: Keel et al. (2016):

https://iopscience.iop.org/article/10.1088/1538-3873/129/971/015002

GCN Circular 32860

Subject
GRB 221009A: Further Gemini-South Infrared Observations
Date
2022-10-27T01:33:55Z (3 years ago)
From
Brendan O'Connor at UMD <oconnorb@umd.edu>
B. O'Connor (UMD/GWU), E. Troja (UTV/ASU), S. Dichiara (PSU),
J. Gillanders (UTV), S. B. Cenko (NASA/GSFC):

We performed target of opportunity observations of GRB 221009A
(Dichiara et al., GCN 32632, Veres et al., GCN 32636)
with the FLAMINGOS-2 spectrograph mounted on the Gemini-South
telescope. Observations began on October 26, 2022 at 23:40:44 UT
corresponding to ~17.4 d after the GRB. We obtained images in
JHK with a total exposure of 75 s in each filter.

The afterglow is clearly detected in each filter. We obtain
the following magnitudes calibrated against the 2MASS catalog:

J = 20.1 +/- 0.2 AB mag
H = 19.43 +/- 0.15 AB mag
K = 18.94 +/- 0.08 AB mag

These magnitudes are not corrected for Galactic extinction.

Further infrared observations are planned.

We acknowledge the staff of the Gemini Observatory for assistance
with these observations.

GCN Circular 32877

Subject
LIGO-Virgo-KAGRA and GEO600 statement on GRB 221009A
Date
2022-10-28T15:30:08Z (3 years ago)
From
Francesco Pannarale at LIGO-Virgo-KAGRA Collaboration <francesco.pannarale@ligo.org>
None of the LIGO, Virgo, or KAGRA detectors were in observing operation
at the time of GRB 221009A. The detectors are currently being prepared
for the O4 observing run, which is expected to begin in March 2023. The
observing run planning can be viewed here:
https://observing.docs.ligo.org/plan/

GEO600 was taking data at the time of GRB 221009A. However, its
sensitivity is insufficient to detect any viable GRB progenitor at the 
estimated z=0.151 (de Ugarte Postigo et al. GCNC 32648), and the data
show no evidence of an astrophysical transient at the time of GRB 221009A.

GCN Circular 32907

Subject
High-precision position of the compact radio counterpart to GRB221009A
Date
2022-11-03T15:45:05Z (3 years ago)
From
Dr. Pikky Atri at ASTRON <atri@astron.nl>
P. Atri (ASTRON), T. An (SHAO), M. Giroletti (INAF-IRA), Y.-K. Zhang (SHAO), J. Bright (Oxford), W. Farah (SETI Institute), Rob Fender (Oxford, UCT), J.-J. Geng (PMO), G. Ghirlanda (INAF - OAB), S. Giarratana (University of Bologna, INAF-IRA), Alexander van der Horst (GWU), Y. Li (PMO), Y. Liu (SHAO), B. Marcote (JIVE), J. C. A. Miller-Jones (ICRAR-Curtin), Sara E. Motta (INAF-OAB, Oxford), M. P�rez-Torres (IAA-CSIC), L. Rhodes (Oxford), O.S. Salafia (INAF - OAB), A. Wang (SHAO), X.-F. Wu (PMO), Z. Xu (SHAO), J. Yang (OSO)

The Very Long Baseline Array (VLBA) observed GRB221009A on 14-15th October 2022 at 2cm (15.2 GHz) to measure the position of the radio counterpart of the GRB with high accuracy (Project code TG015). These were done ~5 days after the GRB was first reported by the Swift Burst Alert Telescope on 9th October 2022 (ATel #15650).

A compact radio source was detected with a >10sigma significance (rms of 0.06 mJy/beam). Fitting a Gaussian elliptical model to the target shows that the peak emission is from the position:

RA 19h13m03s.500792 (2)
Dec 19d46m24s.22891 (7)

Note that the uncertainties here are purely from a fit to the image plane. Due to a 2 arcminutes offset between the pointing position of the VLBA and the position of the GRB, there was a ~25% drop in sensitivity at the location of the GRB. The systematic uncertainties could be of the order of ~0.1mas based on the beamsize of the VLBA and the uncertainties due to the target-calibrator throw are smaller than this. Follow-up observations of GRB221009A will be conducted with the VLBA.

We would like to thank the VLBA schedulers for conducting these service observations for a quick first-epoch look at the GRB.

GCN Circular 32912

Subject
Correction to GCN 32852 (GRB 221009A: SARA-RM 1m Optical Afterglow Detection)
Date
2022-11-05T19:13:51Z (3 years ago)
From
Kyle Pellegrin at Clemson University <pelleg2@g.clemson.edu>
K. Pellegrin,  K. Rumstay, and D. Hartmann report:

The midpoint of observations since the swift trigger stated in GCN 32852
was incorrectly stated at 14.90190 days. The midpoint of observations
occurred on 2022-10-23 at 21:38:42 UTC which makes it 14.3114 days since
the swift trigger on 2022-10-09 at 14:10:17 UTC.

We apologize for any inconvenience this may have caused.

GCN Circular 32916

Subject
GRB 221009A: Extended Bad Time Intervals for Fermi LAT data
Date
2022-11-07T17:38:36Z (3 years ago)
From
Nicola Omodei at Stanford U. <nicola.omodei@slac.stanford.edu>
N. Omodei (Stanford Univ.), P. Bruel (CNRS/IN2P3), J. Bregeon (CNRS/IN2P3), M. Pesce-Rollins (INFN Pisa), D. Horan (CNRS/IN2P3),  E. Bissaldi (Politecnico and INFN Bari), and R. Pillera (Politecnico and INFN Bari) 
report on behalf of the Fermi-LAT team: 

Further investigation of the low-level data has shown that X-ray and soft gamma-ray pile-up, multiple photons being recorded at the same time, impacted a larger time interval than reported in the first GCN (Omodei et al. GCN #32760). 
This very high level of pile-up means that the LAT data cannot be analyzed with the standard tools. 
We have thus extended the Bad Time Interval (BTI) to cover the time between T0+203 and T0+294, where T0 is the Fermi-GBM trigger time, October 9, 2022, at 13:16:59.99 UT.

We are currently working on analysis methods that would allow us to reduce the duration of these BTIs.

The signals in the instrument produced by the 99 GeV photon observed 240 seconds after the GBM trigger were well above the noise due to the GRB induced pile-up. Because the extra energy deposited in the instrument at that time was much less than 99 GeV, we are confident that the photon energy was well reconstructed.

The Fermi-LAT point of contact for this burst is 
Elisabetta Bissaldi (elisabetta.bissaldi@ba.infn.it).

The Fermi-LAT is a pair conversion telescope designed to cover the energy band from 20 MeV to greater than 300 GeV.
It is the product of an international collaboration between NASA and DOE in the U.S. and many scientific institutions across France, Italy, Japan and Sweden.

GCN Circular 32921

Subject
GRB 221009A: Hubble Space Telescope observations
Date
2022-11-08T21:17:06Z (3 years ago)
From
Andrew Levan at U.of Leicester <a.levan@astro.ru.nl>
A.J. Levan (Radboud Univ.), T. Barclay (NASA/GSFC), K. Bhirombhakdi (STScI), E. Burns (LSU), S. B. Cenko (NASA/GSFC), A. A. Chrimes (Radboud Univ.), P. D���Avanzo (INAF/OABr), V. D���Elia (INAF/OAR and ASI/SSDC), M. Della Valle (INAF/OAC), A. de Ugarte Postigo (Obs. Cote d���Azur), W. Fong (Northwestern), A. S. Fruchter (STScI), B. P. Gompertz (Birmingham), D. Hartmann (Clemson University), C. L. Hedges (NASA/GSFC), K. E. Heintz (DAWN/NBI), L. Izzo (DARK/NBI), P. Jakobsson (U. Iceland), P.G. Jonker (Radboud Univ. & SRON), D. A. Kann (Goethe Univ.), J. A. Kennea (PSU), E. Le Floc���h (CEA Paris-Saclay), D. B. Malesani (Radboud Univ. and DAWN/NBI), A. Melandri (INAF/OAR), B. D. Metzger (Columbia and Flatiron/CCA), S. E. Mullally (STScI), E. Pian (INAF, Bologna), S. Piranomonte (INAF/OAR), G. Pugliese (Amsterdam Univ.), J. L. Racusin (NASA/GSFC), J. C. Rastinejad (Northwestern), M. E. Ravasio (Radboud Univ and INAF/OABr), A. Rossi (INAF/OAS), R. Salvaterra (INAF/IASF Milan), B. Sbarufatti (INAF/OABr), B. Schneider (CEA Paris-Saclay), R. L. C. Starling (U. Leicester), N. R. Tanvir (U. Leicester), C. C. Thoene (ASU-CAS), S. D. Vergani (CNRS - Paris Obs.), R. A. M. J. Wijers (Amsterdam), D. Xu (NAOC) report:

We observed the afterglow of GRB 221009A (Dichiara et al., GCN 32632; Kennea & Williams, GCN 32635; Bissaldi et al., GCN 32637; Veres et al., GCN 32636) with the Hubble Space Telescope on 8 November 2022, approximately 30 days after the Fermi/GBM trigger. Observations were obtained in five filters spanning the optical and NIR region (F625W, F775W, F098M, F125W and F160W). 

The optical/IR counterpart is well detected in all images, with provisional AB magnitudes of F625W = 23.61 +/- 0.04, F775W = 22.43 +/- 0.04, F098M = 21.21 +/- 0.01, F125W = 20.63 +/- 0.01, F160W = 20.37 +/- 0.01 mag, based on small apertures around the source location (errors statistical only). After correction for foreground extinction the spectral shape is indicative of a peak around 1 micron, which could be due to the contribution from the associated supernova (de Ugarte Postigo et al. GCN 32800, Belkin et al. GCN 32818, Maiorano et al. GCN 32850).

Inspection of the images reveals faint emission to the NE which is only visible in the NIR bands, and which extends for approximately 1" (2.6 kpc at z = 0.151; de Ugarte Postigo et al., GCN 32648; Castro-Tirado et al. GCN 32686). We suggest this extension is the host galaxy of GRB 221009A and is only visible in the NIR due to foreground extinction. 

Analysis is ongoing, and further observations are planned in late November and early December. 

We thank the staff of STScI, in particular Claus Leitherer, William Januszewski and Joel David Green for their work in rapidly implementing the related DDT proposal (GO 17264, PI Levan).

GCN Circular 32934

Subject
GRB 221009A: GRANDMA/Kilonova-Catcher observations
Date
2022-11-11T17:01:38Z (3 years ago)
From
Damien Turpin at NAOC (CAS) <dturpin-astro@hotmail.com>
O. Aguerre, F. Bayard, E. Broens, H-B. Eggenstein, M. Freeberg, 
R. Kneip (KNC), A. Lekic, B. Delaveau, E. Durand (KNC/IPSA), 
S. Leonini, D. Marchais, E. Maris, R. M�nard, G. Parent, 
M. Richmond, F. Romanov, �M. Serrau, S. Vanaverbeke (KNC), 
S. Antier (OCA/Artemis), D. A. Kann (Goethe Univ.),
S. Karpov (FZU), A. Klotz (OMP/IRAP), T. Midavaine (SAF),
D. Turpin (CEA) report on behalf of GRANDMA and
Kilonova-Catcher collaborations:

The Kilonova-Catcher telescope network responded to the alert of 
the ultra-bright GRB 221009A (Swift detection: Dichiara et al.,
GCN 32632; Fermi GBM detection: Veres et al., GCN 32636). 

In total, 220 science images sent by the KNC amateur astronomers
were analyzed. The KNC observations cover the period from 6.3h 
to about 17.5 days after the Fermi/GBM trigger time.

Below, we report a subset of these observations. Magnitudes are given 
in the AB system and we also report our 5-sigma upper limits.

T-T0 (day)| MJD � | Obser. � |Exposure| Filter | Mag +/- err �|Upp.Lim. (AB)
___________________________________________________________________________
0.285 | 59861.838073 | T-BRO | 5 x 180s | Ic | 15.65 +/- 0.03 | 18.0
0.578 | 59862.131620 | BGO | 60s | I | 16.58 +/- 0.07 | 17.8
1.241 | 59862.794004 | Astrolab IRIS | 14 x 180s | I | 17.47 +/- 0.07 | 18.5
1.365 | 59862.918754 | Ch-Perdrix | 10 x 180s | Clear | 18.76 +/- 0.14 | 19.2
1.447 | 59863.000000 | Ste-Sophie | 16 x 360s | TR-rgb | 18.89 +/- 0.06 | 20.4
1.531 | 59863.084675 | HVO | 59 x 120s | R | 18.93 +/- 0.09 | 19.8
1.703 | 59863.256925 | SRO Auberry | 300s | I | 17.85 +/- 0.13 | 18.1
2.217 | 59863.770555 | Montarrenti | 2 x 30s | Clear | 18.65 +/- 0.24 | 18.5
2.229 | 59863.782465 | EHEA-WL | 199 x 32s | I | 18.64 +/- 0.21 | 18.7
2.267 | 59863.820289 | CO-K26 | 8884s | Lum | -- | 19.7
2.308 | 59863.861789 | GPO | 5700s | Clear | -- | 19.8
2.522 | 59864.075696 | LCO-MDO | 7 x 180s | sdss-r | 19.56 +/- 0.12 | 20.2
2.555 | 59864.108314 | NMSkies | 11 x 300s | Ic | 18.74 +/- 0.13 | 19.3
3.250 | 59864.803399 | Atlas | 30 x 120s | R | -- | 18.4
5.323 | 59866.876810 | Crous Gats | 180 x 32s | TR-rgb | 20.46 +/- 0.14 | 21.0

These detections and limits are consistent with the detections and limits
previously reported in Lipunov et al., GCN 32634; Perley, GCN 32638;
Broens, GCN 32640; Hu et al., GCN 32644; Belkin et al., GCN 32645; GCN 32769
; Wet et al., GCN 32646; Xu et al., GCN 32647; de Ugarte Postigo et al., GCN
32648, 32800; Odeh, GCN 32649; GCN 32666; Brivio et al., GCN 32652; Kuin et al.,
GCN 32656; Paek et al., GCN 32659; Kumar et al., GCN 32662; Romanov, GCN
32664; 32679; Chen et al., GCN 32667; Vidal et al., GCN 32669; Kim et al.,
GCN 32670; Groot et al., GCN 32678; Castro-Tirado et al., GCN 32686;
Watson et al., GCN 32692; Strausbaugh et al. GCN 32693; Butler et al., GCN
32705; Vinko et al., GCN 32709; Mao et al., GCN 32727; Zaznobin et al.,
GCN 32729; Sasada et al., GCN 32730; Strausbaugh & Cucchiara, GCN 32738;
O'Connor et al., GCN 32739; GCN 32750, GCN 32799, GCN 32860; Bikmaev et al.,
GCN 32743; GCN 32752; Rastinejad & Fong, GCN 32749; Schneider et al., GCN
32753; D�Avanzo et al., GCN 32755; Huber et al., GCN 32758; Shrestha et al.,
GCN 32759; 32771; Izzo et al., GCN 32765; Levan et al., GCN 32821, GCN 32921;
Maiorano et al., GCN 32850; Pellegrin et al., GCN 32852.

The GRANDMA/Kilonova-Cacther images have been calibrated using field
stars from the PanSTARRS-DR1 catalog using the STDpipe pipeline
(Karpov 2022).

We advocate a joint multi-wavelength publication for this event and we are 
happy to collaborate with teams that have the same spirit, 
to be able to explore the best astrophysical scenario.

GRANDMA is a worldwide telescope network (grandma.ijclab.in2p3.fr)
devoted to the observation of transients in the context of multi-messenger
astrophysics (Antier et al. 2020 MNRAS 497, 5518). Kilonova-Catcher (KNC) is
the citizen science program of GRANDMA (http://kilonovacatcher.in2p3.fr/).

GCN Circular 32944

Subject
Correction to GCN 32646 (GRB 221009A (Swift J1913.1+1946): MeerLICHT observations)
Date
2022-11-17T11:39:27Z (3 years ago)
From
Simon de Wet at UCT <dwtsim002@myuct.ac.za>
S. de Wet (UCT) reports on behalf of the MeerLICHT consortium:

The r-band magnitude for the afterglow of GRB 221009A reported in GCN 32646
was incorrectly reported as r = 17.76 +/- 0.08 at 18:23:59 UT. The correct
magnitude is r = 16.76 +/- 0.08.

We apologize for any inconvenience this may have caused.

GCN Circular 32949

Subject
GRB 221009A: Japanese VLBI Network observation
Date
2022-11-19T04:37:23Z (3 years ago)
From
Kotaro Niinuma at Yamaguchi University <niinuma@yamaguchi-u.ac.jp>
=========================================================================

K. Niinuma (Yamaguchi Univ.), Y. Yonekura (Ibaraki Univ.), K. Fujisawa, 
K. Motogi (Yamaguchi Univ.), and W. Iwakiri (Chiba Univ.)

We carried out the very long baseline interferometry (VLBI) observations 
of GRB221009A/Swift J1913.1+1946 (Dichiara et al. GCN 32632, ATel 15650) 
at 9:00 - 10:15 UT on October 11, at 8:00 - 9:15 on October 25 and 26, 
2022 (1.82 days, 15.78 days, and 16.78 days after the Fermi-GBM trigger 
(Veres et al. GCN 32632), respectively).

The observation was performed in both C-band (center frequency of 6856 
MHz with a bandwidth of 512 MHz) and X-band (center frequency of 8448 
MHz with a bandwidth of 512 MHz), simultaneously by single baseline 
interferometry consisting of Yamaguchi-34m radio telescope operated by 
Yamaguchi University and Hitachi-32m radio telescope operated by Ibaraki 
University. Both telescopes recorded only left-circular polarization. 
This array is a part of the Japanese VLBI Network and the baseline 
length is of 873 km.

GRB221009A/Swift J1913.1+1946 was successfully detected on October 11, 
and its VLBI flux densities were 13+/���3 mJy at 6.86 GHz and of 11+/-3 
mJy at 8.45 GHz. On the other hand, it was not detected on October 25 
and 26, and the 5-sigma upper limits of VLBI flux density were 3mJy at 
both 6.86GHz and 8.45GHz. The bright quasar J1905+1943 was also observed 
to determine the VLBI flux density of GRB221009A/Swift J1913.1+1946. The 
radio emission from the very compact component detected by our VLBI 
observation showed slightly steep spectrum in radio band on 1.82 days 
after the Fermi-GBM trigger.

=========================================================================



-- 
NIINUMA Kotaro
Graduate School of Sciences and Technology for Innovation,
Yamaguchi Univ., Yoshida 1677-1, Yamaguchi 753-8512, Japan
Phone: +81-(0)83-933-5759
E-mail:niinuma@yamaguchi-u.ac.jp

������ ���������
��������������������� ���������������������
���753-8512 ������������������������������������������

GCN Circular 32973

Subject
GRB 221009A：DAMPE observed a 34.7 GeV photon at 1.36 hour after the GBM trigger
Date
2022-11-23T01:26:16Z (3 years ago)
From
Kai-Kai Duan at Purple Mountain Observatory <duankk@pmo.ac.cn>
Kai-Kai Duan (Purple Mountain Observatory), Zun-Lei Xu (PMO), Zhao-Qiang Shen (PMO), Wei Jiang (PMO), Lu-Yao Jiang (PMO), Dong-Ya Guo (Institute of High Energy Physics), Wen-Xi Peng (IHEP), Fabio Gargano (Istituto Nazionale di Fisica Nucleare) and Xiang Li (PMO), report on behalf of the DAMPE collaboration: 

We report the observation of GRB 221009A with DAMPE, which has been reported by Swift (Kennea et al. GCN #32635, Krimm et al. GCN #32688), Fermi-GBM (Veres et al. GCN #32636, Lesage et al. GCN #32642), Fermi-LAT (Bissaldi et al. GCN #32637, Pillera et al. GCN #32658, Xia et al. GCN #32748), LHAASO (Huang et al. GCN #32677) and so on. 

Though the GRB is about 90 deg from the boresight of DAMPE at the moment of Fermi-GBM trigger (out of the normal FOV), the Unbiased-Trigger counts of DAMPE increased significantly from 227 to 233 seconds after the Fermi-GBM trigger. We believe that about 21 out of 35 events during the 6-second timespan were from the GRB, and the highest deposit energy is 2.4 GeV for these events.  

The FOV of DAMPE began to cover the GRB position about one hour later, and it observed a 34.7 GeV (RA = 289.93 deg, DEC = 19.96 deg) photon at 1.58 deg (with the 95% containment of the PSF as ~ 2 deg) from the swift localization of this GRB (RA = 288.265 deg, Dec = 19.774 deg, from Dichiara et al. GCN #32632) 4896 seconds after the Fermi-GBM trigger. The p-value of this photon emitted from background is 0.0003, corresponding to 3.6-sigma significance locally. During the past 6-year observation, DAMPE observed only one photon with energy above 30 GeV within 2 deg around this GRB position. 

At 9.37 and 16.26 days after the Fermi-GBM trigger, DAMPE observed 8.33 GeV (RA = 287.82 deg, DEC = 20.35 deg) and 10.74 GeV (RA = 287.48 deg, DEC = 19.88 deg) photons around 0.71 deg and 0.75 deg from the LAT localization of GRB 221009A. The local significance of these two photons are 3.10 and 3.22 sigma, respectively. The 95% containment of the PSF above 10 GeV is about 2 deg.  

The detailed data analysis is still on going. 

DAMPE is a satellite for dark matter detection indirectly, cosmic-ray physics and gamma-ray astronomy by detection of the high-energy electrons, cosmic rays and gamma rays.

[Editor's note: Reformatted at the request of the submitter.]

GCN Circular 32995

Subject
Optical polarization observation of GRB 221009A
Date
2022-11-30T22:48:23Z (3 years ago)
From
Ioannis Liodakis at Finnish Centre for Astronomy with ESO <jliodakis@gmail.com>
E. Lindfors (FINCA), K. Nilsson (FINCA), I. Liodakis (FINCA), A. Kasikov 
(NOT, Aarhus University, Tartu Observatory), I. Negueruela (University 
of Alicante)

We observed gamma-ray burst GRB221009A following the GCN alert #32632 
(Dichiara et al., 2022) in optical polarization. The source was observed 
with the Nordic Optical Telescope (NOT) and the ALFOSC instrument in the 
R-band using the standard setup for linear polarization observations 
(lambda/2 retarder followed by a calcite). The observations started 
2022-10-12 at 20:15UT, i.e. approximately 3 days and 6 hours after the 
trigger (2022-10-09 14:10:17 UT). The observations were performed with 
clear sky with seeing 1.2 arcseconds. As the GRB occurred in crowded 
galactic field the ordinary beam image of the GRB221009A ended up behind 
the extraordinary beam of the nearby bright star. Therefore, we had to 
perform careful modelling of the PSF using the second bright star in the 
field of view and subtracted the modeled PSF from the image. We repeated 
this for each image separately. As the PSF subtraction can result in 
some artifacts to the background, we measured the resulting images with 
small aperture of 1.5 arcsec radius. Using the standard formulas, we 
derived a 2 sigma upper limit of 5.1% percent on the polarization degree.

GCN Circular 33038

Subject
GRB 221009A: MuSCAT3 observations
Date
2022-12-10T03:40:25Z (3 years ago)
From
Mariko Kimura at RIKEN <mariko.kimura@riken.jp>
M. Kimura (RIKEN), K. Isogai (Tokyo Univ./Kyoto Univ.), M. Arimoto,
D. Yonetoku (Kanazawa Univ.),
N. Narita, M. Tamura (Tokyo Univ./Astrobiology Center),
A. Fukui�� (Tokyo Univ.), M. Ikoma (NAOJ)

We have monitored the afterglow of GRB 221009A since three days
after the Swift and Fermi alerts (GCN 32632; GCN 32636) by MuSCAT3
on the 2-meter telescope at Las Cumbres Observatory.
MuSCAT3 is multi-channel imagers with the filters of SDSS g', r', i', zs,
which is designed for observing transiting exoplanets.
https://lco.global/observatory/instruments/muscat3/

The measurements are here:
BJD���������������������������������������� Mag������ Err���� Filter
2459864.82404�� 21.33�� 0.15�� g
2459864.82404�� 20.01�� 0.03�� r
2459864.82404�� 19.48�� 0.03�� i
2459864.82404�� 18.26�� 0.01�� z
2459870.80681�� 23.55�� 0.21�� g
2459870.80681�� 21.74�� 0.05�� r
2459870.80681�� 20.47�� 0.04�� i
2459870.80681�� 19.90�� 0.03�� z
2459872.82760�� 23.64�� 0.26�� g
2459872.82760�� 21.91�� 0.07�� r
2459872.82760�� 20.82�� 0.06�� i
2459872.82760�� 20.22�� 0.05�� z
2459876.80690�� 23.99�� 0.34�� g
2459876.80690�� 21.96�� 0.09�� r
2459876.80690�� 21.00�� 0.08�� i
2459876.80690�� 20.50�� 0.07�� z

By plotting these data with the other optical measurements reported to GCN
(GCNs 32625, 32640, 32644, 32645, 32646, 32652, 32659, 32662, 32666,
32667, 32670, 32678, 32679, 32692, 32693, 32705, 32709, 32729, 32730,
32743, 32750, 32758, 32769, 32771, 32799, 32809, 32818),
we found that the optical afterglow light curve shows a power-law decay, and
only i'-band light curve fluctuates along the decline possibly because of
systematic errors.
We did not find a bump reported by GCN 32818 at least around a week after
the Swift and Fermi trigger.

If you have any queries, please contact M. Kimura at the following address.
mariko.kimura@riken.jp

GCN Circular 33243

Subject
GRB 221009A: radio afterglow detection with the EVN
Date
2023-02-01T10:41:25Z (2 years ago)
From
Stefano Giarratana at University of Bologna <s.giarratana@ira.inaf.it>
S. Giarratana (University of Bologna, INAF-IRA), M. Giroletti 
(INAF-IRA), T. An (Shanghai A.O.), G. Anderson (Curtin University), P. 
Atri (ASTRON), J. S. Bright (University of Oxford), R. Fender 
(University of Oxford), G. Ghirlanda (INAF-OAB), J. K. Leung (University 
of Sydney, CSIRO), B. Marcote (JIV-ERIC), M. P��rez-Torres (IAA-CSIC), L. 
Rhodes (University of Oxford), O. S. Salafia (INAF-OAB), J. Yang (OSO)

On UT 2022 November 18 and 21 (40 and 43 days post-burst) we observed 
the radio counterpart of GRB 221009A (Dichiara et al, GCN 32632; Veres 
et al., GCN 32636) with the European VLBI Network (EVN) at a central 
frequency of 8.3 and 5 GHz, respectively.

 From a preliminary analysis, the source is clearly detected at both 
frequencies with >30 sigma significance. The 8.3 GHz surface brightness 
peak is ~1.3 mJ/beam. The synthesized beam is 0.9 x 0.5 mas (PA = 7.7 
deg). The 5 GHz surface brightness peak is ~1.4 mJy/beam. The 
synthesized beam is 1.7 x 0.9 mas (PA = 9.25 deg).

The source is found at a position within ~1 mas of the one previously 
reported by Atri et al., GCN 32907 with the VLBA at 15.2 GHz. The offset 
is most likely accounted for by systematics.

All the results presented here are preliminary. Further analysis is in 
progress. We will report the final results in a forthcoming publication.

We would like to thank the directors and staff of all the EVN telescopes 
for approving, executing, and processing these out-of-session ToO 
observations.

The European VLBI Network is a joint facility of independent European, 
African, Asian, and North American radio astronomy institutes. 
Scientific results from data presented in this publication are derived 
from the following EVN project code: RG013.

GCN Circular 33305

Subject
GRB 221009A: Continued Swift Observations
Date
2023-02-08T18:41:45Z (2 years ago)
From
Maia Williams at Penn State <mjw6837@psu.edu>
M. Williams (PSU) reports on behalf of the Swift Team:

Swift resumed observations of GRB 221009A on February 7 at 00:51 UTC after the end of Sun constraint, ~10 Ms after the Fermi/GBM trigger (Veres et al., GCN Circ. 32636). The X-ray afterglow is still faintly detectable (1.9 x 10^-3 counts s^-1) in a 9.4 ks XRT exposure.

Further observations are planned for this weekend.
Questions or comments?
Contact GCN directly.
Have you found a bug in GCN?
Open an issue.
Want to contribute code to GCN?
Get involved on GitHub.

gcn.nasa.gov

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