GRB 120907A
GCN Circular 13716
Subject
GRB 120907A: Swift detection of a burst with optical counterpart
Date
2012-09-07T00:38:43Z (13 years ago)
From
Scott Barthelmy at NASA/GSFC <scott@milkyway.gsfc.nasa.gov>
J. L. Racusin (NASA/GSFC), S. D. Barthelmy (GSFC),
W. H. Baumgartner (GSFC/UMBC), D. N. Burrows (PSU),
N. Gehrels (NASA/GSFC), S. T. Holland (STScI), J. A. Kennea (PSU),
N. P. M. Kuin (UCL-MSSL), F. E. Marshall (NASA/GSFC),
K. L. Page (U Leicester), D. M. Palmer (LANL),
T. Sakamoto (NASA/UMBC), B. Sbarufatti (INAF-OAB/PSU) and
M. H. Siegel (PSU) report on behalf of the Swift Team:
At 00:24:23 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 120907A (trigger=532871). Swift slewed immediately to the burst.
The BAT on-board calculated location is
RA, Dec 74.741, -9.314 which is
RA(J2000) = 04h 58m 58s
Dec(J2000) = -09d 18' 48"
with an uncertainty of 3 arcmin (radius, 90% containment, including
systematic uncertainty). The BAT light curve shows a single pulse
with a duration of about 5 sec. The peak count rate
was ~2000 counts/sec (15-350 keV), at ~2 sec after the trigger.
The XRT began observing the field at 00:25:45.1 UT, 82.0 seconds after
the BAT trigger. Using promptly downlinked data we find an uncatalogued
X-ray source with an enhanced position: RA, Dec 74.7494, -9.3143 which
is equivalent to:
RA(J2000) = 04h 58m 59.86s
Dec(J2000) = -09d 18' 51.3"
with an uncertainty of 2.1 arcseconds (radius, 90% containment). This
location is 29 arcseconds from the BAT onboard position, within the BAT
error circle. This position may be improved as more data are received;
the latest position is available at http://www.swift.ac.uk/sper.
A power-law fit to a spectrum formed from promptly downlinked event
data gives a column density consistent with the Galactic value of 5.35
x 10^20 cm^-2 (Kalberla et al. 2005).
UVOT took a finding chart exposure of 250 seconds with the U filter starting
142 seconds after the BAT trigger. There is a candidate afterglow in the
rapidly available 2.7'x2.7' sub-image at
RA(J2000) = 04:59:00.01 = 74.75005
DEC(J2000) = -09:18:54.2 = -9.31505
with a 90%-confidence error radius of about 0.63 arc sec. This position is 4.6
arc sec. from the center of the XRT error circle. The estimated magnitude is
17.63 with a 1-sigma error of about 0.15. No correction has been made for the
expected extinction corresponding to E(B-V) of 0.09.
Burst Advocate for this burst is J. L. Racusin (judith.racusin AT nasa.gov).
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.)
GCN Circular 13717
Subject
GRB 120907A: ROTSE-III Optical Limits
Date
2012-09-07T00:59:19Z (13 years ago)
From
Weikang Zheng at U.of Michigan <zwk@umich.edu>
W. Zheng (U Mich), H. Flewelling (IfA/Hawaii), report on behalf of the ROTSE
collaboration:
ROTSE-IIId, located at the Turkish National Observatory at Bakirlitepe,
Turkey, automatically responded to GRB 120907A (Swift trigger 532871;
Racusin et al., GCN 13716). An automated response took the first image at
00:31:23.7 UT, 420 s after the burst, under fair conditions. We took 10
5-sec, 10 20-sec and 0 60-sec exposures. These unfiltered images are
calibrated relative to USNO A2.0 (R). Imaging is on going.
We do not detect the candidate afterglow reported in GCN 13716. Individual
images have limiting magnitudes ranging from 14.0-15.4; we set the following
specific limits.
start UT end UT t_exp(s) mlim t_start-tGRB(s) Coadd?
--------------------------------------------------------------------
00:31:23.7 00:31:07.0 5 14.8 420 N
00:31:23.7 00:33:35.0 50 15.8 420 Y
00:33:40.0 00:38:20.0 200 16.4 557 Y
GCN Circular 13718
Subject
GRB 120907A MASTER optical observations
Date
2012-09-07T02:35:27Z (13 years ago)
From
Vladimir Lipunov at Moscow State U/Krylov Obs <gcncirc@observ.inetcomm.ru>
E. Gorbovskoy, V. Lipunov, V.Kornilov, D.Kuvshinov, A.Belinski, N.Tyurina,
N.Shatskiy, P.Balanutsa, D.Zimnukhov, A.Kuznetsov, V.V.Chazov,
A.Kuznetsov, A.Sankovich
Moscow Lomonosov State University, Sternberg Astronomical Institute,
K.Ivanov, S.Yazev, N.M.Budnev, O.Gres, O.Chuvalaev, V.A.Poleshchuk
Irkutsk State University
V.Yurkov, Yu.Sergienko, D.Varda, E.Sinyakov
Blagoveschensk Educational State University, Blagoveschensk
A. Tlatov, A.V. Parhomenko, D. Dormidontov, V.Sennik
Kislovodsk Solar Station of the Pulkovo Observatory
V.Krushinski, I.Zalozhnich, A. Popov, A. Bourdanov, A. Punanova
Ural Federal University
Hugo Levato and Carlos Saffe
Instituto de Ciencias Astronomicas, de la Tierra y del Espacio (ICATE)
Claudio Mallamaci, Carlos Lopez and Federico Podest
Observatorio Astronomico Felix Aguilar (OAFA)
MASTER II robotic telescope (MASTER-Net: http://observ.pereplet.ru)
located in Kislovodsk was pointed to the GRB120907A 375 s after notice
time and 389 sec after GRB time at 2012-09-07 00:30:52 UT in a two
polarizations.
We are marginaly see SWIFT-UVOT optical transient (J. L. Racusin et. al.
GCN 13716) on out first images.
The unfiltred OT magnitude is about 17.5 mag.
The long pointing time was due to some technical issues.
The message may be cited.
GCN Circular 13719
Subject
GRB 120907A: NOT optical observations
Date
2012-09-07T06:51:15Z (13 years ago)
From
Thomas Kruehler at Dark Cosmology Center <tom@dark-cosmology.dk>
T. Kruehler (DARK/NBI), D. Xu (WIS) and S. Schulze (PUC and MCSS) report on behalf of a larger collaboration:
We observed the field of the Swift GRB 120907A (Racusin et al., GCN 13716) with the NOT telescope equipped with StanCam. Eight I-band images with integration times of 120 s each were obtained on 2012-09-07 starting at 03:49 UT, which is roughly 3.4 hours after the trigger.
The optical afterglow (Racusin et al., GCN 13716) is clearly detected in our images. We derive a preliminary magnitude of
I = 20.2 +/- 0.1
centered at approximatly 3.6 hours after the trigger and assuming that the USNO star at RA(J2000) = 04:58:58.52, decl.(J2000) = -09:18:00.7 has an I-band magnitude of 15.28. An additional systematic uncertainty in the absolute brightness of about 0.3 mag is expected due to the calibration against the USNO catalog.
We are grateful to the NOT staff and observer, Anlaug Amanda Djupvik, for obtaining these observations.
GCN Circular 13720
Subject
GRB 120907A: Swift-BAT refined analysis
Date
2012-09-07T14:46:18Z (13 years ago)
From
Scott Barthelmy at NASA/GSFC <scott@lheamail.gsfc.nasa.gov>
M. Stamatikos (OSU), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC),
J. R. Cummings (GSFC/UMBC), E. E. Fenimore (LANL), N. Gehrels (GSFC),
H. A. Krimm (GSFC/USRA), C. B. Markwardt (GSFC), D. M. Palmer (LANL),
J. L. Racusin (NASA/GSFC), T. Sakamoto (GSFC/UMBC), G. Sato (ISAS),
J. Tueller (GSFC), T. N. Ukwatta (MSU)
(i.e. the Swift-BAT team):
Using the data set from T-61 to T+242 sec from recent telemetry downlinks,
we report further analysis of BAT GRB 120907A (trigger #532871)
(Racusin, et al., GCN Circ. 13714). The BAT ground-calculated position is
RA, Dec = 74.736, -9.323 deg which is
RA(J2000) = 04h 58m 56.7s
Dec(J2000) = -09d 19' 21.2"
with an uncertainty of 2.0 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 21%.
The mask-weighted light curve shows 2 or 3 somewhat overlapping peaks
starting at ~T-1 sec, peaking at ~T+1 sec, and ending at ~T+20 sec.
T90 (15-350 keV) is 16.9 +- 8.9 sec (estimated error including systematics).
The time-averaged spectrum from T-0.04 to T+18.76 sec is best fit by a simple
power-law model. The power law index of the time-averaged spectrum is
1.73 +- 0.25. The fluence in the 15-150 keV band is 6.7 +- 1.1 x 10^-7 erg/cm2.
The 1-sec peak photon flux measured from T+0.10 sec in the 15-150 keV band
is 2.9 +- 0.4 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/532871/BA/
GCN Circular 13721
Subject
GRB 120907A: Fermi GBM detection
Date
2012-09-07T15:27:07Z (13 years ago)
From
George A. Younes at USRA/NASA/MSFC <younes.ge@gmail.com>
George Younes (MSFC/USRA) reports on behalf of the Fermi GBM Team:
"At 00:24:24.51 UT on 07 September 2012, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 120907A (trigger 368670267 / 120907017)
which was also detected by the Swift/BAT (Barthelmy et al. 2012, GCN 13716).
The GBM on-ground location is consistent with the Swift position.
The angle from the Fermi LAT boresight is 110 degrees.
The GBM light curve consists of a single pulse with a duration (T90)
of about 5.8 s (50-300 keV).
The time-averaged spectrum from T0-1.4 s to T0+0.7 s is
best fit by a power law function with an exponential high-energy cutoff.
The power law index is -0.75 +/- 0.25 and the cutoff energy,
parameterized as Epeak, is 154.50 +/- 32.90 keV.
The event fluence (10-1000 keV) in this time interval is
(7.8 +/- 1.1)E-07 ergs/cm^2. The 1-sec peak photon flux measured
starting from T0-1.1 s in the 10-1000 keV band
is 4.3 +/- 0.4 ph/s/cm^2.
The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog."
GCN Circular 13722
Subject
GRB 120907A: Enhanced Swift-XRT position
Date
2012-09-07T16:07:31Z (13 years ago)
From
Phil Evans at U of Leicester <pae9@star.le.ac.uk>
M.R. Goad, J.P. Osborne, A.P. Beardmore and P.A. Evans (U. Leicester)
report on behalf of the Swift-XRT team.
Using 4509 s of XRT Photon Counting mode data and 5 UVOT
images for GRB 120907A, we find an astrometrically corrected X-ray
position (using the XRT-UVOT alignment and matching UVOT field sources
to the USNO-B1 catalogue): RA, Dec = 74.74990, -9.31501 which is equivalent
to:
RA (J2000): 04h 58m 59.98s
Dec (J2000): -09d 18' 54.0"
with an uncertainty of 1.6 arcsec (radius, 90% confidence).
This position may be improved as more data are received. The latest
position can be viewed at http://www.swift.ac.uk/xrt_positions. Position
enhancement is described by Goad et al. (2007, A&A, 476, 1401) and Evans
et al. (2009, MNRAS, 397, 1177).
This circular was automatically generated, and is an official product of the
Swift-XRT team.
GCN Circular 13723
Subject
GRB 120907A: Spectroscopy from OSIRIS/GTC
Date
2012-09-07T16:35:20Z (13 years ago)
From
Antonio de Ugarte Postigo at IAA-CSIC <deugarte@iaa.es>
R. Sanchez-Ramirez, J. Gorosabel (IAA-CSIC), A. de Ugarte Postigo
(IAA-CSIC, DARK/NBI) and J.M. Gonzalez Perez (GTC) report
on behalf of a larger collaboration:
We have obtained spectroscopy of the afterglow of GRB 120907A
(Racusin et al. GCN 13716) with OSIRIS/ GTC (La Palma, Spain) on
Sep 7.20647-7.23893 UT (4.55-5.33 hours post GRB). The observation
consisted of 3x900s exposures using the R1000R grating, covering the
range from 5100 to 10000 A with a resolution of ~1100.
In the combined spectrum we detect several absorption features
corresponding to FeII, MgII, MgI and CaII at a common redshift of z=0.970,
which we identify as the redshift of the GRB.
We acknowledge the excellent support of the GTC staff.
GCN Circular 13724
Subject
GRB 120907A: Swift-XRT refined Analysis
Date
2012-09-07T16:38:07Z (13 years ago)
From
Phil Evans at U of Leicester <pae9@star.le.ac.uk>
A. Maselli (INAF-IASFPA), V. Mangano (INAF-IASFPA), A. Melandri
(INAF-OAB), J.A. Kennea (PSU), M.C. Stroh (PSU), D.N. Burrows (PSU),
J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), C. Pagani (U.
Leicester) and J.L. Racusin report on behalf of the Swift-XRT team:
We have analysed 16 ks of XRT data for GRB 120907A (Racusin et al. GCN
Circ. 13716), from 93 s to 46.4 ks after the BAT trigger. The data
comprise 76 s in Windowed Timing (WT) mode with the remainder in Photon
Counting (PC) mode. The enhanced XRT position for this burst was given
by Goad et al. (GCN. Circ 13722).
The late-time light curve (from T0+4.5 ks) can be modelled with a
power-law decay with a decay index of alpha=1.02 (+/-0.08).
A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.91 (+0.13, -0.12). The
best-fitting absorption column is 10.0 (+3.1, -2.9) x 10^20 cm^-2, in
excess of the Galactic value of 5.4 x 10^20 cm^-2 (Kalberla et al.
2005). The counts to observed (unabsorbed) 0.3-10 keV flux conversion
factor deduced from this spectrum is 3.8 x 10^-11 (4.7 x 10^-11) erg
cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
Total column: 10.0 (+3.1, -2.9) x 10^20 cm^-2
Galactic foreground: 5.4 x 10^20 cm^-2
Excess significance: 2.7 sigma
Photon index: 1.91 (+0.13, -0.12)
The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00532871.
This circular is an official product of the Swift-XRT team.
GCN Circular 13725
Subject
GRB 120907A: Swift/UVOT Detection
Date
2012-09-07T19:17:57Z (13 years ago)
From
Samantha Oates at MSSL <sro@mssl.ucl.ac.uk>
S. R. Oates (MSSL-UCL) and J. L. Racusin (NASA/GSFC)
report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 120907A
142 s after the BAT trigger (Racusin et al., GCN Circ. 13716).
A source consistent with the enhanced XRT position (Goad et al. GCN Circ. 13722)
is detected in the initial UVOT exposures.
The preliminary UVOT position is:
RA (J2000) = 04:59:00.00 = 74.75002 (deg.)
Dec (J2000) = -09:18:54.0 = -9.31501 (deg.)
with an estimated uncertainty of 0.52 arc sec. (radius, 90% confidence).
Preliminary detections and 3-sigma upper limits using the UVOT photometric system
(Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the early exposures are:
Filter T_start(s) T_stop(s) Exp(s) Mag
v 449 6811 471 >19.5
b 398 567 39 19.02 +/- 0.29
u 142 392 246 17.67 +/- 0.08
w1 498 666 40 18.27 +/- 0.32
m2 473 1122 79 18.68 +/- 0.36
w2 424 642 39 18.56 +/- 0.37
The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.09 in the direction of the burst
(Schlegel et al. 1998).
GCN Circular 13726
Subject
GRB 120907A: EVLA observations
Date
2012-09-08T16:47:19Z (13 years ago)
From
Tanmoy Laskar at Harvard U <tanmoylaskar@gmail.com>
T. Laskar, A. Zauderer and E. Berger (Harvard) report:
"We observed the position of GRB 120907A (GCN 13716) with the EVLA
beginning 2012 September 7.46 UT (10.5 hours after the burst). No
significant radio emission is detected at the enhanced Swift-XRT position
(GCN 13724), the UVOT position (GCN 13725) or optical position (GCN 13719).
Preliminary analysis indicates a three-sigma upper limit of 75 uJy at 5.8
GHz. Further observations are planned."
--
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
3rd Yr Graduate Student in Astronomy
Harvard-Smithsonian Center for Astrophysics
A-107, 60 Garden St, Cambridge (617)-495-5989
http://www.cfa.harvard.edu/~tlaskar
Mobile: (617)-899-9361
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
GCN Circular 13743
Subject
GRB 120907A: SMA upper limits
Date
2012-09-11T02:18:39Z (13 years ago)
From
Ashley Zauderer at CfA <bevinashley@gmail.com>
G. Petitpas (SAO), A. Zauderer, T. Laskar, E. Berger (Harvard) report
on behalf of the SMA Rapid Transients (SMART) Key Project:
"We observed the position of GRB 120907A (Racusin et al; GCN 13716)
with the Submillimeter Array (SMA) beginning 2012 Sep 7.63 UT (dt ~ 0.6
d). At a mean frequency of 230 GHz, we do not detect significant radio
emission within the enhanced Swift/XRT error circle (Goad et al; GCN
13702) to a 3-sigma upper limit of 2.7 mJy. Beginning 2012 Sep 8.5 UT
(dt ~ 1.5 d), we repeated our observations, and report a 3-sigma upper
limit of 2.4 mJy.
We thank the SMA Observatory staff for its support."
GCN Circular 13761
Subject
GRB 120907A: optical observations of ISON-Kislovodsk
Date
2012-09-13T18:53:47Z (13 years ago)
From
Alexei Pozanenko at IKI, Moscow <apozanen@iki.rssi.ru>
V. Nevski (ISON-Kislovodsk Observatory), A. Volnova (SAI MSU/IKI), I.
Molotov (KIAM), A. Pozanenko (IKI) report on behalf of larger
collaboration:
We observed the field of GRB 120907A (Racusin et al., GCN 13716) with
Santel-400AN (0.4-m f/3) telescope �f ISON-Kislovodsk observatory starting
on Sep. 07 (UT) 00:34:32, i.e. ~10.2 minutes after burst trigger. We took
several unfiltered images of 30 s and 60 s exposures. In a stacked images
we clearly detect optical afterglow of GRB 120907A (Racusin et al., GCN
13716; Gorbovskoy et al., GCN 13718; Kruehler et al., GCN 13719). A
preliminary photometry of stacked frames is based on the USNO-B1.0 (R2)
nearby stars:
T_start, T0+, Exp, Filter, OT
(UT) mid (d) (s)
00:34:32 0.00899 10x30 none 18.55+/-0.09
00:51:45 0.02120 5x60 none 18.95+/-0.13
00:58:09 0.02980 8x60 none 19.52+/-0.20
01:16:32 0.04339 8x60 none 19.50+/-0.20