GRB 220921A
GCN Circular 32618
Subject
GRB 220921A: ATCA detection of radio counterpart
Date
2022-10-03T06:49:53Z (4 years ago)
From
James Leung at U of Sydney/VAST <jleu9465@uni.sydney.edu.au>
James Leung (University of Sydney/CSIRO), Ziteng Wang (University of
Sydney/CSIRO), Emil Lenc (CSIRO), Tara Murphy (University of Sydney)
The Australia Telescope Compact Array (ATCA) observed GRB 220921A
(Pillera et al., GCN 32568) at multiple frequencies starting on 2022
September 28, from 16:30 to 21:00 UTC (7.2 to 7.4d post-trigger).
We detect a radio source in all bands at the position:
RA (J2000) = 04:25:53.4
Dec (J2000) = -40:24:20.5
with uncertainty ~0.5" in each coordinate, which is consistent with
the MASTER optical (Lipunov et al., GCN 32570) and ALMA mm (Laskar
et al., GCN 32577) candidate afterglow positions.
We report our preliminary flux density measurements below:
Freq (GHz) | Peak Flux Density (micro-Jy/beam)
----------------------------------------------
5.5 | 163 +/- 19
9.0 | 364 +/- 17
16.7 | 763 +/- 50
21.2 | 988 +/- 95
Ongoing observations are planned.
We thank CSIRO staff for rapidly scheduling and supporting these
observations.
GCN Circular 32596
Subject
GRB 220921A: LCOGT Optical Observations
Date
2022-09-27T18:10:04Z (4 years ago)
From
Robert Strausbaugh at University of Minnesota <rstrausb@umn.edu>
R. Strausbaugh (University of Minnesota), A. Cucchiara (College of Marin)
report on behalf of a larger collaboration:
We observed the Fermi-LAT detection GRB 220921A (Pillera et al., GCN 32568)
field with the Las Cumbres Observatory Global Telescope Network (LCOGT)
1-meter Sinistro instrument at the South African Astronomical Observatory
site, on September 22, from 00:18 to 00:45 (corresponding to 13.22 to 14.57
hours from the GRB trigger time) with the Bessel I and R filters.
We performed a series of 3x300s exposures in R and I bands. We detect the
MASTER optical afterglow candidate (Lipunov et al., GCN 32570), in both
bands, consistent with other optical detections (de Wet et al., GCN 32572;
Watson et al., GCN 32576).
The following magnitudes are calculated using the USNO-B1 catalog as
reference:
R= 18.02 +/- 0.27
I= 17.78 +/- 0.36
We also observed the afterglow of GRB 220921A with the LCOGT 1-meter
Sinistro instrument at the Cerro Tololo Interamerican Observatory, Chile
site, on September 23, from 04:50 to 05:18 (corresponding to 41.75 to 42.22
hours from the GRB trigger time) with the Bessel I and R filters.
We performed a series of 3x300s exposures in R and I bands. We detect the
MASTER optical afterglow candidate (Lipunov et al., GCN 32570) in both
bands.
The following magnitudes are calculated using the USNO-B1 catalog as
reference:
R= 19.26 +/- 0.34
I= 19.03 +/- 0.39
These magnitudes are not corrected for galactic extinction. Further
observations are planned.
GCN Circular 32582
Subject
GRB 220921A: further MeerLICHT observations
Date
2022-09-25T15:34:07Z (4 years ago)
From
Simon de Wet at UCT <dwtsim002@myuct.ac.za>
S. de Wet (UCT), P.J. Groot (Radboud/UCT/SAAO) and D.A.H Buckley (SAAO)
report on behalf of the MeerLICHT consortium:
The 0.6m wide-field MeerLICHT telescope obtained a total of six 300s
exposures in the qugrizq bands in order to monitor the evolving afterglow
of GRB 220921A. Observations started at 00:34:09 UT on September 24,
approximately 2.56 days post-trigger. We detect the afterglow with a SNR >
5 in the qugri bands and with a SNR of 3.8 in the z band. We report the
following magnitudes:
u = 20.63 +/- 0.21
g = 20.52 +/- 0.10
q = 20.23 +/- 0.04
r = 20.16 +/- 0.10
i = 20.24 +/- 0.14
z = 19.91 +/- 0.28
We note that the source is continuing to fade.
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 32577
Subject
GRB 220921A: ALMA detection
Date
2022-09-23T16:37:36Z (4 years ago)
From
Tanmoy Laskar at U of Bath <tanmoylaskar@gmail.com>
T. Laskar (University of Utah), K. D. Alexander (University of Arizona), E.
Berger (Harvard University), R. Chornock (UC Berkeley), W. Fong
(Northwestern University), R. Margutti (UC Berkeley), C. G. Mundell
(University of Bath), and P. Schady (University of Bath) report on behalf
of a larger collaboration:
"We observed GRB 220921A (Pillera et al., GCN 32568) with the Atacama Large
Millimeter/Submillimeter Array (ALMA) at 97.5 GHz beginning on 2021
September 23 08:04 UT (45 h after the burst). Preliminary analysis reveals
a mm source with flux density of ~ 0.7 mJy at position:
RA (J2000) = 04:25:53.42
Dec (J2000) = -40:24:20.25
with uncertainty ~ 0.01" in each coordinate, consistent with the X-ray
position (N. Klinger, GCN 32571) and optical position (Lipunov et al., GCN
32570). Further observations are planned.
We thank the JAO staff, AoD, P2G, and the entire ALMA team for their help
with these observations."
GCN Circular 32576
Subject
GRB 220921A: DDOTI Detection of the Afterglow
Date
2022-09-23T14:19:41Z (4 years ago)
From
Alan M Watson at UNAM <alan@astro.unam.mx>
Alan M. Watson (UNAM), Nat Butler (ASU), Rosa L. Becerra (UNAM), Simone
Dichiara (PSU), Diego Gonzalez (UNAM), Alexander Kutyrev (GSFC/UMD),
William H. Lee (UNAM), Oc��lotl Lopez (UNAM), Margarita Pereyra (UNAM),
and Eleonora Troja (GSFC/UMD) report:
We observed the field of the Fermi/LAT GRB 220921A (Pillera et al., GCN
Circ. 32568) with the DDOTI wide-field imager at the Observatorio
Astron��mico Nacional on Sierra San Pedro Martir
(http://ddoti.astroscu.unam.mx) from 2022-09-23 11:51 to 12:24 UTC
(48.75 to 49.30 hours after the trigger) obtaining 2040 seconds of
exposure.
At the position of the OT detected by MASTER-Net (Lipunov et al., GCN
Circ. 32570) we detect a source with w = 19.31 +/- 0.13. We calibrate
our photometry against the APASS catalog.
The afterglow has continued to fade from the observations reported by
Lipunov et al. (GCN Circ. 32570) and de Wet et al. (GCN Circ. 32572).
We thank the staff of the Observatorio Astron��mico Nacional in San Pedro
Martir.
GCN Circular 32575
Subject
Konus-Wind detection of GRB 220921A
Date
2022-09-22T18:47:23Z (4 years ago)
From
Dmitry Svinkin at Ioffe Institute <svinkin@mail.ioffe.ru>
D. Svinkin, D. Frederiks, M. Ulanov, A. Tsvetkova,
A. Lysenko, A. Ridnaia, and T. Cline
on behalf of the Konus-Wind team, report:
The bright, long-duration GRB 220921A
(Fermi-LAT detection: Pillera et al., GCN Circ. 32568;
Fermi-GBM detection: Bissaldi, GCN Circ. 32574)
triggered Konus-Wind at T0=39961.714 s UT (11:06:01.714).
The burst light curve shows the bright multipeaked initial
emission episode which starts at ~T0-3.7 s and ends at ~T0+38 s,
followed by a weaker episode at T0+220 s.
The total duration of ~231 s.
The emission is seen up to ~8 MeV.
The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB220921_T39961/
As observed by Konus-Wind, the burst
had a fluence of 9.71(-2.95,+2.35)x10^-5 erg/cm2,
and a 64-ms peak flux, measured from T0+9.216 s,
of 1.44(-0.25,+0.26)x10^-5 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).
The time-averaged spectrum of the burst
(measured from T0 to T0+257.536 s)
is best fit in the 20 keV - 8 MeV range
by the GRB (Band) model with the following parameters:
the low-energy photon index alpha = -0.88(-0.47,+0.67),
the high energy photon index beta = -2.07(-0.50,+0.15),
the peak energy Ep = 126(-36,+85) keV
(chi2 = 93/78 dof).
The spectrum near the maximum count rate
(measured from T0+6.656 to T0+11.776 s)
is best fit in the 20 keV - 8 MeV range
by the GRB (Band) model with the following parameters:
the low-energy photon index alpha = -0.89(-0.14,+0.20),
the high energy photon index beta = -2.26(-0.19,+0.14),
the peak energy Ep = 203(-35,+36) keV
(chi2 = 106/78 dof).
All the quoted errors are at the 90% confidence level.
All the quoted values are preliminary.
GCN Circular 32574
Subject
GRB 220921A: Fermi GBM detection
Date
2022-09-22T17:01:16Z (4 years ago)
From
Elisabetta Bissaldi at INFN,Bari <elisabetta.bissaldi@ba.infn.it>
E. Bissaldi (Politecnico and INFN Bari)
reports on behalf of the Fermi GBM Team:
"At 11:05:59.071 UT on 21 September 2022, the Fermi Gamma-Ray Burst Monitor (GBM)
triggered and located GRB 220921A (trigger 685451164/ 220921462), which was also
detected by Fermi-LAT (Pillera et al. 2022, GCN #32568).
The on-ground calculated location, using the GBM trigger data, is
RA = 66.85, DEC = -40.0
(J2000 degrees, equivalent to 04h 27m, -40d 00'),
with a statistical uncertainty of 1 degree (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]).
The Fermi GBM on-ground Localization is consistent
with the Fermi-LAT position.
The angle from the Fermi LAT boresight
at the GBM trigger time is 69 degrees.
The GBM light curve consists of multiple emission episodes
with a duration (T90) of about 210 s (50-300 keV).
The time-averaged spectrum from T0 to T0+40 s is
best fit by a Band function with Epeak = 142 +/- 4 keV,
alpha = -0.90 +/- 0.02, and beta = -2.09 +/- 0.02.
The event fluence (10-1000 keV) in this time interval is
(5.92 +/- 0.04)E-05 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+11 s in the 10-1000 keV band
is 36.2 +/- 0.4 ph/s/cm^2.
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 32572
Subject
GRB 220921A: MeerLICHT afterglow observations
Date
2022-09-22T10:02:05Z (4 years ago)
From
Simon de Wet at UCT <dwtsim002@myuct.ac.za>
S. de Wet (UCT), P.J. Groot (Radboud/UCT/SAAO) and D.A.H Buckley (SAAO)
report on behalf of the MeerLICHT consortium:
Following the detection of GRB 220921A by Fermi/LAT (Pillera et al., GCN
32568), the 0.6m wide-field MeerLICHT telescope, located at Sutherland,
South Africa, obtained a repeated series of 60s exposures of a field
encompassing the entire LAT error box in the q,u,g,r,i,z bands following
the sequence quqgqrqiqz. Observations started at 01:29:34 UT on September
22 and continued for approximately two hours.
We detect the previously reported afterglow to GRB 220921A at a position
consistent with the MASTER and Swift/XRT positions (Lipunov et al., GCN
32570; Kingler et al., GCN 32571) with the following AB magnitudes at a
mid-time of September 22 01:46:00 UT, 0.61 days after the LAT trigger time:
u = 19.28 +/- 0.14
g = 18.64 +/- 0.03
q = 18.47 +/- 0.02
r = 18.43 +/- 0.04
i = 18.25 +/- 0.05
z = 18.24 +/- 0.11
We note that the source is exhibiting fading behaviour with respect to the
previously reported MASTER brightness (Lipunov et al., GCN 32570).
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 32571
Subject
GRB 220921A: Swift-XRT Observations
Date
2022-09-22T02:55:44Z (4 years ago)
From
Noel Klingler at NASA-GSFC / UMBC <njk5441@psu.edu>
Swift-XRT has performed follow-up observations of the Fermi-LAT-detected
burst GRB 220921A, collecting 4.1 ks of Photon Counting (PC) mode data
between T0+27.4 and T0+40.7 ks.
An uncatalogued X-ray source has been detected consistent with being within
17.3 arcmin from the center of the Fermi-LAT position (which is within its
90% error radius of 25.19 arcmin; Pillera et al., GCN 32568), and being
consistent with the optical transient detected by MASTER (Lipunov et al.,
GCN 32570). The source's peak flux (8.6 (+/- 1.9) * 10^-12 erg cm^-2 s^-1)
is 7.6-�� above the RASS limit, and it is fading with 2.9-�� significance.
Source 1:
RA (J2000.0): 66.47255 = 04:25:53.41
Dec (J2000.0): -40.4057 = -40:24:20.4
Error: 3.8 arcsec (radius, 90% conf.)
Count-rate: (0.20 [+/- 0.04]) ct s^-1
Distance: 17.3 arcsec from Fermi-LAT position
Exposure: 1328 s (vignetting corrected)
Two other uncatalogued sources were also detected within the GRB position.
The results of the XRT-team automatic analysis of the XRT observations,
including a position-specific upper limit calculator, are available at
https://www.swift.ac.uk/xrt_products/TILED_GRB00107/.
Further observations are pending.
This circular is an official product of the Swift-XRT team.
GCN Circular 32570
Subject
GRB 220921A: MASTER OT inside Fermi-LAT error-box
Date
2022-09-21T22:44:10Z (4 years ago)
From
Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru>
V.Lipunov (Lomonosov MSU), D.A.H.Buckley (SAAO),
N.Tiurina, A.Kuznetsov, O.Gress, E.Gorbovskoy, G.Antipov,
P.Balanutsa, K.Zhirkov, A.Chasovnikov, D.Vlasenko, V.Senik, D.Kuvshinov,
V.Topolev,Ya.Kechin, Yu.Tselik (Lomonosov Moscow State University, SAI, Physics Department),
C.Francile, R. Podesta, C.Lopez, F. Podesta (Observatorio Astronomico Felix Aguilar OAFA),
R. Rebolo, M. Serra (The Instituto de Astrofisica de Canarias),
L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez, A.Corella,
L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory),
N.M.Budnev (ISU,API),
A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory),
A. Gabovich, V.Yurkov (Blagoveschensk Educational State University)
MASTER OT J042553.42-402420.7 discovery as possibly counterpart of GRB 220921A
AT2022vjw
MASTER-SAAO auto-detection system ( Lipunov et al., "MASTER Global Robotic Net", Advances in Astronomy, 2010, 30L )
discovered OT source at (RA, Dec) = 04h 25m 53.42s -40d 24m 20.7s on
2022-09-21.82255 UT during Fermi trigger 685451164 inspection(T0=2022-09-21 11:05:59.07)
(Lipunov et al. GCN 32569, Fermi-LAT GCN 32568, also detected by GECAM-B)
https://master.sai.msu.ru/site/master2/event.php?id=2097239 .
The OT unfiltered magnitude is 17.8m (automatic), mlim=19.8.
The OT is seen in 24 images. There is no minor planet at this place.
We have 600 reference images without any OT since 2014, for ex., on
2018-11-12.98741 UT with unfiltered mlim=20.3m.
Spectral observations are required.
There is possible host galaxy in VIZIER database (DES, rmag=24.3)
The message may be cited.
GCN Circular 32568
Subject
GRB 220921A: Fermi-LAT detection
Date
2022-09-21T19:17:34Z (4 years ago)
From
Roberta Pillera at Politecnico and INFN Bari <roberta.pillera@ba.infn.it>
R. Pillera (Politecnico and INFN Bari), E. Bissaldi (Politecnico and
INFN Bari),
N. Di Lalla (Stanford Univ.) report on behalf of the Fermi-LAT team:
At 11:05:59.07 UTC on September, 21, 2022 Fermi-LAT detected high-energy
emission from GRB 220921A,
which was also detected by Fermi GBM (trigger 685451164 / 220921462).
The best LAT on-ground location is found to be
RA, Dec = 66.79, -40.25 (J2000)
with an error radius of 0.42 deg (90 % containment, statistical error
only).
This was 69 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 0-2000 s after the
GBM trigger
is (3.1 +/- 0.1)E-06 ph/cm2/s.
The estimated photon index above 100 MeV is -2.1 +/- 0.3.
The highest-energy photon is a 866 MeV event which is observed 935
seconds after the GBM trigger.
A Swift ToO has been requested for this burst.
The Fermi-LAT point of contact for this burst is
Roberta Pillera (roberta.pillera@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 32567
Subject
GRB 220921A: Tiled Swift observations
Date
2022-09-21T18:43:03Z (4 years ago)
From
Phil Evans at U of Leicester <pae9@leicester.ac.uk>
P. A. Evans (U. Leicester) reports on behalf of the Swift team:
Swift has initiated a series of observations, tiled on the sky, of the
Fermi/LAT GRB 220921A. Automated analysis of the XRT data will
be presented online at http://www.swift.ac.uk/xrt_products/TILED_GRB00107
Any uncatalogued X-ray sources detected in this analysis will be
reported on this website and via GCN COUNTERPART notices. The probability of finding
serendipitous sources, unrelated to the Fermi/LAT event is high: any X-ray source
considered to be a probable afterglow candidate will be reported via a GCN Circular
after manual consideration.
Details of the XRT automated analysis methods are detailed in Evans et
al. (2007, A&A, 469, 379; 2009, MNRAS, 397, 1177 and 2014, ApJS, 210, 8).
This circular is an official product of the Swift-XRT team.