GRB 090621B
GCN Circular 9764
Subject
GRB 090621B: MAGIC telescope GeV observation
Date
2009-08-11T07:10:46Z (16 years ago)
From
Markus Garczarczyk at MPI/MAGIC <garcz@mppmu.mpg.de>
Carosi A. (INAF Rome), Gaug M. (IAC Tenerife),
Antonelli L.A. (INAF Rome), Bastieri D. (Univ. Padova),
Becerra Gonzalez J. (IAC Tenerife), Covino S. (INAF Rome),
Galante N. (MPI Munich), Garczarczyk M. (IFAE Barcelona),
La Barbera A. (INAF Palermo), Longo F. (INFN Trieste),
Scapin V. (Univ. Udine) and Spiro S. (INAF Rome)
for the MAGIC collaboration
The MAGIC Imaging Atmospheric Cherenkov Telescope performed a follow-up
observation of the BAT short burst GRB090621B (Curran et al., GCN Circ.
9545). The burst was also triggered by Fermi-GBM (Goldstein et al., GCN
Circ. 9562). We received the GCN alert at 22:07:38 UT (T0+13s). Data
taking with MAGIC started at 22:43:33 UT (T0+2169s), when the GRB zenith
angle went below 60 degrees. The observation continued for 12570 s.
No evidence for VHE gamma-ray emission above the analysis threshold was
found.
A preliminary analysis, for the hypothesis of steady emission and
assumption of a differential photon spectral index of -2.5, yields the
following 95% CL differential flux upper limits, including a 30%
systematic uncertainty on the telescope efficiency.
Because of improving sensitivities and analysis threshold due to
decreasing zenith angle during the observation, the data sample
was split into 4 parts:
E ( 300-1000 GeV): 0.42 * 10^-10 erg cm^-2 s^-1
for a time window from 22:43:33 UT to 23:38:37 UT
Analysis threshold: 407 GeV
E ( 175- 300 GeV): 5.61 * 10^-10 erg cm^-2 s^-1
E ( 300-1000 GeV): 0.19 * 10^-10 erg cm^-2 s^-1
for a time window from 23:38:37 UT to 00:32:31 UT
Analysis threshold: 291 GeV
E ( 175- 300 GeV): 4.97 * 10^-10 erg cm^-2 s^-1
E ( 300-1000 GeV): 0.24 * 10^-10 erg cm^-2 s^-1
for a time window from 00:32:31 UT to 01:23:06 UT
Analysis threshold: 224 GeV
E ( 125- 175 GeV): 15.27 * 10^-10 erg cm^-2 s^-1
E ( 175- 300 GeV): 1.25 * 10^-10 erg cm^-2 s^-1
E ( 300-1000 GeV): 0.22 * 10^-10 erg cm^-2 s^-1
for a time window from 01:23:06 UT to 02:13:04 UT
Analysis threshold: 186 GeV
We can also exclude emission of a constant flux in any 100s time bin
smaller than:
E ( 300-1000 GeV): 4.02 * 10^-10 erg cm^-2 s^-1
for a time window from 22:43:33 UT to 23:38:37 UT
Analysis threshold: 407 GeV
E ( 175- 300 GeV): 23.60 * 10^-10 erg cm^-2 s^-1
E ( 300-1000 GeV): 1.52 * 10^-10 erg cm^-2 s^-1
for a time window from 23:38:37 UT to 00:32:31 UT
Analysis threshold: 291 GeV
E ( 175- 300 GeV): 15.33 * 10^-10 erg cm^-2 s^-1
E ( 300-1000 GeV): 1.41 * 10^-10 erg cm^-2 s^-1
for a time window from 00:32:31 UT to 01:23:06 UT
Analysis threshold: 224 GeV
E ( 125- 175 GeV): 22.23 * 10^-10 erg cm^-2 s^-1
E ( 175- 300 GeV): 7.87 * 10^-10 erg cm^-2 s^-1
E ( 300-1000 GeV): 1.15 * 10^-10 erg cm^-2 s^-1
for a time window from 01:23:06 UT to 02:13:04 UT
Analysis threshold: 186 GeV
This message can be cited.
GCN Circular 9656
Subject
GRB 090621B: MTM-500 optical observations
Date
2009-07-11T20:19:43Z (16 years ago)
From
Alexei Pozanenko at IKI, Moscow <apozanen@iki.rssi.ru>
A. Pozanenko (IKI), A. Volnova (SAI MSU), V. Kouprianov, Ya. Naiden, V.
Slesarenko, A. Devyatkin (Pulkovo Observatory), report on behalf of larger
GRB follow-up collaboration:
We observed the field of the Swift GRB 090621B (Curran et al, GCN 9545)
with MTM-500 telescope of Kislovodsk solar station of the Pulkovo
observatory in two series in R-filter between (UT) 2009-06-21 22:31 -
2009-06-22 00:01, i.e. starting ~24 minutes after burst onset. The upper
limit of a stacked image of first 15 frames based on USNO B1.0 stars is
following
T0+ Filter Exp. mag.
(mid, d) s
0.02147 R 15x60 >18.5 (3 sigma)
While we do not detect objects reported in GCN 9547 (Levan et al.) and GCN
9549 (Galeev et al.) in the stacked image above, we may suggest a possible
object near the edge of the refined XRT error box (Beardmore et al., GCN
9550) in coordinates (J2000) RA = 20:53:53.24 Dec = +69:01:45.5. This
possible object appears more intense in the stacked image of the first five
frames, and does not appear in the second epoch of our observations started
on Jun.21 (UT) 23:37. Due to low S/N ratio we cannot confirm the object is
real. We encourage re-analysis of later deep observations to clarify the
nature of the object.
The finding chart can be found at
http://grb.rssi.ru/GRB090621B/grb090621B_MTM.png , where source labeled #5
is the USNO B1.0 star 1590-0172172 (RA(J2000)=20:53:57.28,
Dec(J2000)=+69:01:47.8, R2=19.41)
GCN Circular 9565
Subject
GRB 090621B: GRT Optical Observation
Date
2009-06-23T02:18:16Z (16 years ago)
From
Takanori Sakamoto at NASA/GSFC <takanori.sakamoto-1@nasa.gov>
T. Sakamoto (UMBC/GSFC), D. Donato (ORAU/GSFC), N. Gehrels (GSFC),
T. Okajima (JHU/GSFC), T.N. Ukwatta (GWU/GSFC), Y. Urata (NCU),
C.A. Wallace (FGCU)
We observed the field of GRB 090621B detected by Swift
(trigger #355359; Curran et al., GCN #9545) with the 14-inch
Goddard Robotic Telescope (GRT) located at the Goddard Geophysical
and Astronomical Observatory (http://cddisa.gsfc.nasa.gov/ggao/).
100 set of 30 sec exposures were taken in the R filter starting
from June 22 01:51:44 (UT) about 3.7 hours after the trigger and
stopped on June 22 02:47:51 (UT). We do not detect the optical
afterglow both in the individual images and the combined image
inside the XRT position (Beardmore et al., GCN #9550). The
estimated three sigma upper limit of the combined image (total
exposure of 2880 sec; excluding four bad quality images) is
~17.8 mag using the USNO-B1 catalog.
GCN Circular 9562
Subject
GRB 090621B: Fermi GBM detection
Date
2009-06-23T00:03:11Z (16 years ago)
From
Adam Goldstein at Fermi-GBM/UAH <adam.m.goldstein@msfc.nasa.gov>
A. Goldstein (UAH) and J.M. Burgess (UAH)
report on behalf of the Fermi GBM Team:
"At 22:07:25.70 UT on 21 June 2009, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 090621B (trigger 267314847 / 090621922)
which was also detected by the Swift BAT (P.A. Curran et al. 2009,
GCN 9545). The GBM on-ground location is consistent with the
Swift position. The angle from the Fermi LAT boresight
is 108 degrees.
The GBM light curve consists of one short spike
with a duration (T90) of about 0.128 s (8-1000 keV).
The time-averaged spectrum from T0-0.064 s to T0+0.064 s is
best fit by a Band function with Epeak = 321.60 +/- 129.00 keV,
alpha = -0.13 +/- 0.38, and beta = -1.57 +/- 0.08
(chi squared 401 for 481 d.o.f.).
The event fluence (8-1000 keV) in this time interval is
(3.71 +/- 0.58)E-07 erg/cm^2. The 0.128-sec peak photon flux measured
starting from T0-0.064 s in the 8-1000 keV band
is 6.4 +/- 1.4 ph/s/cm^2.
The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog."
GCN Circular 9561
Subject
GRB 090621B: I-band observations from 1.23m CAHA
Date
2009-06-22T20:05:29Z (16 years ago)
From
Javier Gorosabel at IAA-CSIC <jgu@iaa.es>
J. Gorosabel (IAA-CSIC), P. Kubanek (GACE and IAA-CSIC), S. Mottola
(DLR), U. Carsenty (DLR), A. Levan (U. Warwick), M. Jelinek (IAA-
CSIC), A.J. Castro-Tirado (IAA-CSIC), A. de Ugarte Postigo (ESO, INAF/
OAB), report on behalf of a larger collaboration:
"Following the detection of the short-hard GRB 090621B by SWIFT
(Curran et al. GCNC 9545) we carried out I-band observations with the
1.23m telescope at Observatory of Calar Alto. The observations were
done on June 22.094-22.161 UT (4.14-5.75 hours post burst) with a
total exposure time of 22x240s. The candidates reported by Levan et
al. (GCNC 9547) and Galeev (GCNC 9549) are preliminarily detected at
I~22.5 and I~20.6, respectively, against USNO-B field stars."
GCN Circular 9559
Subject
GRB 090621B: Gemini spectrum of afterglow candidate
Date
2009-06-22T19:42:32Z (16 years ago)
From
Edo Berger at Harvard <eberger@cfa.harvard.edu>
E. Berger (Harvard), A. Cucchiara, D.B. Fox (Penn State), and A.J. Levan
(U. Warwick) report:
"On 2009 June 22.41 UT we used the GMOS instrument mounted on the
Gemini-North 8-m telescope to obtain spectroscopic observations of the
candidate optical afterglow (GCN #9547) of the short GRB 090621B (GCN
#9545). A pair of 1800 sec exposures were obtained with a wavelength
coverage of 4500-7500A. The combined spectrum of the source reveals
broad features typical of an early M dwarf star. We therefore conclude
that this object is unrelated to the GRB."
GCN Circular 9557
Subject
GRB 090621B: P60 Observations
Date
2009-06-22T17:40:24Z (16 years ago)
From
S. Bradley Cenko at Caltech <cenko@srl.caltech.edu>
S. B. Cenko (UC Berkeley), A. J. Levan (U. Warwick), M. M. Kasliwal, S. R.
Kulkarni (Caltech) report on behalf of a larger collaboration:
We have imaged the field of the short GRB090621B (Curran et al., GCN 9545)
with the automated Palomar 60-inch telescope. Observations consisted of
20 x 180 s images in the i' filter at a mean epoch of 5:37 UT on 22 June
2009 (~ 7.5 hours after the burst).
We detect the candidate afterglow reported by Levan et al. (GCN 9547) and
Galeev et al. (GCN 9549) at low significance. Using several USNO-B
sources in the field for reference, we measure a magnitude of I ~ 22.9.
No other sources are detected inside the revised XRT error circle
(Beardmore et al., GCN 9550).
Directly comparing our P60 image with the WHT image from ~ 2 hours after
the burst (GCN 9547), we find the candidate has faded marginally by 0.5 +-
0.3 mag. Further late-time observations will be needed to confirm if this
is the optical afterglow of GRB090621B.
GCN Circular 9555
Subject
GRB 090621B: VLA observations
Date
2009-06-22T16:03:04Z (16 years ago)
From
Edo Berger at Harvard <eberger@cfa.harvard.edu>
E. Berger and W.-f. Fong (Harvard) report:
"We observed the field centered on the XRT error circle of the short GRB
090621B (GCNs #9545,9550) with the VLA at a frequency of 8.46 GHz
starting on 2009 June 22.53 UT (14.6 hours post burst). We do not
detect any sources within the refined XRT error circle to a 3-sigma
limit of 54 microJy."
[GCN OPS NOTE(22jun09): Per author's request, the missing "B"
was added to the GCN name.]
GCN Circular 9552
Subject
GRB 090621B: Swift/UVOT Upper Limits
Date
2009-06-22T13:45:39Z (16 years ago)
From
Peter Curran at MSSL <pac@mssl.ucl.ac.uk>
P.A. Curran (MSSL-UCL) reports on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 090621B
76s after the BAT trigger (Curran et al., GCN 9545). No optical
afterglow consistent with the refined XRT position (Beardmore et al.,
GCN 9550) or the optical source observed by Levan et al. (GCN 9547) is
detected in the UVOT exposures.
Preliminary 3-sigma upper limits using the UVOT photometric system
(Poole et al. 2008, MNRAS, 383, 627) for the first exposures are:
Filter T_start(s) T_stop(s) Exp(s) Mag
wh 76 18173 1221 >22.29
v 618 10774 1142 >20.67
b 544 23952 1986 >21.88
u 289 29731 2675 >21.77
uw1 668 29017 2882 >21.63
um2 643 28110 2006 >21.32
uw2 594 6589 432 >20.50
The values quoted above are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.44 in the direction of the burst
(Schlegel et al. 1998).
GCN Circular 9551
Subject
GRB 090621B: Swift-BAT refined analysis
Date
2009-06-22T13:08:54Z (16 years ago)
From
Scott Barthelmy at NASA/GSFC <scott@lheamail.gsfc.nasa.gov>
H. A. Krimm (GSFC/USRA), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC),
J. R. Cummings (GSFC/UMBC), P.A. Curran (MSSL-UCL), E. E. Fenimore (LANL),
N. Gehrels (GSFC), C. B. Markwardt (GSFC/UMD), D. M. Palmer (LANL),
A. M. Parsons (GSFC), T. Sakamoto (GSFC/UMBC), G. Sato (ISAS),
M. Stamatikos (GSFC/ORAU), J. Tueller (GSFC), T. N. Ukwatta (GWU)
(i.e. the Swift-BAT team):
Using the data set from T-239 to T+963 sec from the recent telemetry downlink,
we report further analysis of BAT short hard burst GRB 090621B (trigger #355359)
(Curran, et al., GCN Circ. 9545). The BAT ground-calculated position is
RA, Dec = 313.455, 69.034 deg, which is
RA(J2000) = 20h 53m 49.3s
Dec(J2000) = +69d 02' 02.9"
with an uncertainty of 1.7 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 69%.
The mask-weighted light curve shows a single peak starting a ~T+0 sec
and ending at ~T+0.2 sec. There is a 2.5-sigma hint of extended emission
from ~T+150 to ~T+240 sec. T90 (15-350 keV) is 0.14 +- 0.04 sec
(estimated error including systematics).
The time-averaged spectrum from T-0.028 to T+0.148 sec is best fit by a simple
power-law model. The power law index of the time-averaged spectrum is
0.82 +- 0.23. The fluence in the 15-150 keV band is 7.0 +- 1.0 x 10^-8 erg/cm2.
The 1-sec peak photon flux measured from T-0.44 sec in the 15-150 keV band
is 3.9 +- 0.5 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/355359/BA/
GCN Circular 9550
Subject
GRB 090621B: Swift-XRT refined analysis
Date
2009-06-22T10:16:55Z (16 years ago)
From
Andy Beardmore at U Leicester <apb@star.le.ac.uk>
A.P. Beardmore, K.L. Page (U. Leicester) and P.A. Curran (UCL-MSSL)
report on behalf of the Swift-XRT team:
We have analysed five orbits of Swift-XRT photon counting (PC) mode data
from GRB 090621B (Curran et al., GCN Circ. 9545), spanning the interval
T+80 s to T+19.5 ks after the trigger. In 10.0 ks we find a refined XRT
position of RA, Dec = 313.47049, 69.02845, which is equivalent to
RA (J2000) = 20:53:52.92
Dec(J2000) = +69:01:42.4
with an uncertainty of 4.0 arcsec (90% containment). This position
is 1.2 arcsec from the XRT position quoted in GCN Circ. 9545.
The X-ray light-curve shows a faint, fading source with a decay index
of 0.61 +/- 0.19. If the source continues to decay at the same rate
we predict an XRT count rate of 8.6e-4 count s^-1 at T+24 hours.
The PC mode spectrum from T+80 s to T+17.1 ks can be fit by an absorbed
powerlaw with a photon index of 1.47+/-0.66, assuming a Galactic column
density of 1.9e21cm^-2 in the direction of the burst. The observed
(unabsorbed) 0.3-10keV flux for this model is 3.8e-13 (4.5e-13)
erg cm^-2 s^-1.
This circular is an official product of the Swift-XRT team.
GCN Circular 9549
Subject
GRB 090621B: RTT150 optical observations
Date
2009-06-22T09:55:15Z (16 years ago)
From
Rodion Burenin at IKI, Moscow <rodion@hea.iki.rssi.ru>
A. Galeev, I. Bikmaev, N. Sakhibullin (KSU/AST),
R. Burenin, M. Pavlinsky, R. Sunyaev (IKI),
I. Khamitov, Z. Eker (TUG), U. Kiziloglu (METU), E. Gogus (Sabanci Uni.)
report:
We observed the field of the Swift-BAT GRB 090621B (Curran et al., GCN9545)
with Russian-Turkish 1.5-m telescope (RTT150, Bakirlitepe, TUBITAK National
Observatory, Turkey), starting at 21 Jun, 22:52:55 UT, i.e. approximately 45
minutes after the burst, using TFOSC.
We made 3x300s exposures in Rc band. On combined image we do not detect any
new source inside the XRT error circle (Curran et al., GCN 9545) besides the
source reported by Levan et. al. (GCN 9547), which is detected only
marginally. There is also one more brighter point-like source
(RA=20:53:51.25, DEC=+69:01:37.4, J2000) outside but close to the edge of
XRT error circle. Using USNO-B1 stars we estimate its magnitude as
m_Rc=21.8+/-0.06. The limiting magnitude of combined image is m_Rc ~23.6.
The finding chart can be found at:
http://hea.iki.rssi.ru/grb/090621b/indexeng.html
GCN Circular 9547
Subject
GRB 090621B: Optical Observations
Date
2009-06-22T01:41:48Z (16 years ago)
From
Andrew Levan at U.of Leicester <A.J.Levan@warwick.ac.uk>
A.J. Levan (U. Warwick), P. Curran (MSSL), K. Wiersema (U. Leicester)
and P. Groot (Nijmegen) report:
"We observed the location of the short GRB 090621B (Curran et al. GCN
9545) with the WHT, beginning at 23:48:33 UT. Observations were
obtained in the i-band, with a total exposure time of 1800s. Inside
the XRT error box we find a faint object at
RA = 20 53 53.07
Dec = +69 01 40.8
with errors of approximately 0.5" in each axis. The object is
significantly fainter than the DSSII limit, and shows no obvious
variability between the first and last exposures (taken ~1.7 and
~2.3 hours post burst). Given the relatively high foreground
extinction the probability of a chance alignment within the XRT
error box is non-trivial. Hence we are unable to make strong
statements about the association of this source with GRB 090621B
at this stage."
GCN Circular 9545
Subject
GRB 090621B: Swift detection of a short hard burst
Date
2009-06-21T22:38:35Z (16 years ago)
From
Scott Barthelmy at NASA/GSFC <scott@lheamail.gsfc.nasa.gov>
P.A. Curran (MSSL-UCL), S. D. Barthelmy (GSFC),
A. P. Beardmore (U Leicester), D. N. Burrows (PSU),
N. Gehrels (NASA/GSFC), J. A. Kennea (PSU),
C. B. Markwardt (CRESST/GSFC/UMD), F. E. Marshall (NASA/GSFC),
D. M. Palmer (LANL), A. Rowlinson (U Leicester),
T. Sakamoto (NASA/UMBC), P. Schady (MSSL-UCL), M. C. Stroh (PSU) and
H. Ziaeepour (UCL-MSSL) report on behalf of the Swift Team:
At 22:07:25 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 090621B (trigger=355359). Swift slewed immediately to the burst.
The BAT on-board calculated location is
RA, Dec 313.432, +69.013 which is
RA(J2000) = 20h 53m 44s
Dec(J2000) = +69d 00' 48"
with an uncertainty of 3 arcmin (radius, 90% containment, including
systematic uncertainty). The BAT light curve shows a single spike
with a duration less than 128 millisec. The peak count rate
was ~7000 counts/sec (15-350 keV), at ~0 sec after the trigger.
The XRT began observing the field at 22:08:36UT, 70.7 s after the BAT trigger.
In promptly downlinked data, XRT found a faint uncatalogued source at RA, Dec
(J2000) = 313.4700, 69.0282, which is
RA = 20h 53m 52.8s
Dec = +69d 01' 41.5"
with an uncertainty of 8.0 arcseconds (radius, 90% containment). This
location is 73 arcseconds from the BAT onboard position, within the BAT
error circle.
UVOT took a finding chart exposure of nominal 150 seconds with the
White filter starting 76 seconds after the BAT trigger. No credible
afterglow candidate has been found in the initial data products at
the XRT position. Data from the 2.7'x2.7' sub-image are not available
at this time. The 8'x8' region for the list of sources generated
on-board covers 100% of the BAT error circle. The list of sources is
typically complete to about 18 mag. No correction has been made for
the expected extinction corresponding to E(B-V) of 0.43 (Schlegel et
al. 1998).
Burst Advocate for this burst is P.A. Curran (pac AT mssl.ucl.ac.uk).
Please contact the BA by email if you require additional information
regarding Swift followup of this burst. In extremely urgent cases, after
trying the Burst Advocate, you can contact the Swift PI by phone (see
Swift TOO web site for information: http://www.swift.psu.edu/too.html.)