GRB 070917
GCN Circular 6791
Subject
GRB 070917: Swift detection of a bright burst
Date
2007-09-17T07:48:46Z (18 years ago)
From
Jay R. Cummings at NASA/GSFC/Swift <jayc@milkyway.gsfc.nasa.gov>
J. R. Cummings (NASA/UMBC), A. P. Beardmore (U Leicester),
P. A. Evans (U Leicester), N. Gehrels (NASA/GSFC),
C. B. Markwardt (CRESST/GSFC/UMD), P. T. O'Brien (U Leicester),
K. L. Page (U Leicester), D. M. Palmer (LANL),
T. Sakamoto (NASA/ORAU) and M. Stamatikos (NASA/ORAU) report on
behalf of the Swift Team:
At 07:33:56 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 070917 (trigger=291292).
The BAT on-board calculated location is RA, Dec 293.925, +2.413 which is
RA(J2000) = 19h 35m 42s
Dec(J2000) = +02d 24' 47"
with an uncertainty of 3 arcmin (radius, 90% containment, including
systematic uncertainty). The BAT light curve showed a FRED
structure with a duration of about 5 sec. The peak count rate
was ~22000 counts/sec (15-350 keV), at ~0 sec after the trigger.
Because Swift is in the process of returning to normal operations,
automatic slewing to GRBs is currently disabled. Therefore, there
are no prompt XRT or UVOT observations of this burst.
Burst Advocate for this burst is J. R. Cummings (jayc AT milkyway.gsfc.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 6792
Subject
GRB 070917, Swift-BAT refined analysis
Date
2007-09-17T14:34:18Z (18 years ago)
From
Scott Barthelmy at NASA/GSFC <scott@lheamail.gsfc.nasa.gov>
J. Tueller (GSFC), L. Barbier (GSFC), S. D. Barthelmy (GSFC),
J. Cummings (GSFC/UMBC), E. Fenimore (LANL), N. Gehrels (GSFC),
H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD), D. Palmer (LANL),
T. Sakamoto (GSFC/ORAU), G. Sato (GSFC/ISAS), M. Stamatikos (GSFC/ORAU),
T. Ukwatta (GWU)
(i.e. the Swift-BAT team):
Using the data set from T-120 to T+129 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 070917 (trigger #291292)
(Cummings, et al., GCN Circ. 6791). The BAT ground-calculated position is
RA, Dec = 293.923, 2.420 deg which is
RA(J2000) = 19h 35m 41.5s
Dec(J2000) = 02d 25' 12"
with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 79%.
The mask-weighted lightcurve starts at ~T-5 sec, has a sharp rise from
T-0.1 sec to ~T+0.3 sec, peaks at ~T+0.4 sec, and then approximately
exponentially decays to background at ~T+30 sec.
T90 (15-350 keV) is 7.3 +- 0.2 sec (estimated error including systematics).
The time-averaged spectrum from T-0.1 to T+11.4 sec is best fit by a simple
power-law model. The power law index of the time-averaged spectrum is
1.52 +- 0.05. The fluence in the 15-150 keV band is 2.0 +- 0.1 x 10^-6 erg/cm2.
The 1-sec peak photon flux measured from T+0.21 sec in the 15-150 keV band
is 8.5 +- 0.3 ph/cm2/sec. All the quoted errors are at the 90% confidence
level.
GCN Circular 6793
Subject
GRB 070917: R band observations
Date
2007-09-17T16:47:00Z (18 years ago)
From
Kuntal Mishra at ARIES,Nainital,India <kuntal@aries.ernet.in>
K. Misra, S. B. Pandey and Rupak Roy (ARIES, NainiTal, India, on bahalf
of larger Indian GRB collaboration)
We have imaged the field of Swift GRB 070917 with the 1.04m telescope at
NainiTal ~ 7.5 hours after the burst (Cummings et al. GCN 6791).
Observations were performed in R band (5*300 sec) in poor sky conditions.
We notice that the field is crowded and a considerable amount of
extinction (E(B - V) = 0.45 mag) is there in the burst direction. Visual
comparison with DSS-II plate does not show any new source within the
refined error-box (Tueller et al. GCN 6792). Photometry of the co-added
frame put a 3 sigma upper limit of ~20.5 mag in comparison to the nearby
USNO A2.0 star 0900-15768267 (R mag 16.6)
This message may be cited.
GCN Circular 6794
Subject
GRB 070917: MITSuME Akeno Ic upper limit
Date
2007-09-17T19:10:51Z (18 years ago)
From
Nobuyuki Kawai at Tokyo Tech <nkawai@hp.phys.titech.ac.jp>
T. Ishimura, T. Shimokawabe, N. Vasquez, Y. Yatsu, Y. Kudou and
N. Kawai (Tokyo Tech) report on behalf of the MITSuME collaboration:
We observed the field of GRB070917 (Cummings et al. GCN 6791)
with the 3-color 50cm MITSuME Telescope at Akeno, Japan starting
at 09:46:58 UT, 2.2 hours after the trigger.
Although the observation was performed in three bands (Ic, Rc, and g'),
only the data in Ic band are usable for reliable comparison to
catalogued sources because of the poor sky condition in the dusk
with thin clouds.
We did not detect a new source in the BAT error circle. The 3-sigma
limiting magnitude based on USNO-B1.0 (I-band) stars is following.
Filter start time end time Exposure Mag (3-sigma UL)
-----------------------------------------------------------
Ic 09:46:58$B!!(B 10:08:08$B!!!!(B13 x 60s 17.8
-----------------------------------------------------------
GCN Circular 6795
Subject
GRB 070917: KAIT optical limits
Date
2007-09-17T23:05:15Z (18 years ago)
From
Weidong Li at UC Berkeley KAIT/LOSS <weidong@astron.berkeley.edu>
W. Li, University of California, Berkeley, on behalf of the KAIT GRB
team, report:
The robotic 0.76-m Katzman Automatic Imaging Telescope (KAIT)
at Lick Observatory observed GRB 070917 detected with Swift
(Trigger 291292; Cummings et al. GCN 6791, Tueller et al. GCN
6792). The automatic sequence started at 07:34:52, 56 s after
the burst. The BAT location has been monitored in V, I, and
clear filters, with varying exposure times. Our image processing
pipeline did not find any new objects within the BAT error circle,
with the following photometry limits (calibrated with USNO B1.0).
These magnitudes have not been corrected for Galactic extinction
(E(B - V) = 0.45 mag; Misra et al. GCN 6793).
======================================================================
Start UT t(GRB) Filter Exp(s) 3sigma-limit
07:34:52 56s clear 5.0 16.8
07:34:58 62s clear 5.0 16.7
07:35:04 68s clear 5.0 16.8
07:35:10 74s clear 5.0 16.7
07:35:17 81s clear 5.0 16.9
07:35:48 112s V 20.0 16.2
07:36:19 143s I 20.0 17.3
07:36:49 173s clear 20.0 17.9
========================================================================
More images, mostly 20 s exposures in the I and clear filters,
have been obtained. No obvious OA was found in the BAT error
circle to a limiting magnitude of 16.9 - 18.0 mag, at
t= 204 s to 2204 s after the burst.
This message may be cited.
GCN Circular 6796
Subject
GRB 070917: Swift-XRT observations
Date
2007-09-18T08:53:44Z (18 years ago)
From
Phil Evans at U of Leicester <pae9@star.le.ac.uk>
P.A. Evans, A.P. Beardmore, K.L. Page, R.L.C. Starling (U. Leicester)
and J.R. Cummings (NASA/UMBC) report on behalf of the Swift-XRT team:
We have analysed 2.3 ks of Swift XRT data for GRB 070917 (Cummings et
al. GCN Circ 6791) beginning 35 ks after the trigger. The data are
entirely in Photon Counting mode. An uncatalogued X-ray source is
clearly detected at RA, Dec= 293.91913, +2.41055 degrees, which is
equivalent to:
RA (J2000) = 19h 35m 40.59s
Dec(J2000) = +02d 24' 38.0"
with an estimated uncertainty of 8.0 arcsec (radius, 90% containment
including boresight uncertainty). This is 37 arcsec from the BAT refined
position (Tueller et al. GCN Circ 6792). The source has a count rate of
0.016 counts s^-1. At present we are unable to determine whether the
source is fading, however observations are ongoing.
Using the C-statistic in xspec we fit the PC mode spectrum from
T0+35000-42000 s with an absorbed power-law. The absorption is
consistant with the Galactic value of 1.73e21 cm^-2 (Kalberla et al.
2005). The spectral slope is gamma=1.17 (+0.44/-0.45), which is
consistent with the BAT value of 1.52 +/- 0.04. The observed
(unabsorbed) flux is 1.31e-12 (1.44e-12) erg/cm^2/s.
This circular is an official product of the Swift team.
GCN Circular 6798
Subject
Konus-Wind observation of GRB 070917
Date
2007-09-18T11:56:48Z (18 years ago)
From
Valentin Pal'shin at Ioffe Inst <val@mail.ioffe.ru>
S. Golenetskii, R.Aptekar, E. Mazets, V. Pal'shin, D. Frederiks,
and T. Cline on behalf of the Konus-Wind team report:
The long GRB 070917 (Swift-BAT trigger #291292:
Cummings et al., GCN 6791; Tueller et al., GCN 6792) triggered
Konus-Wind at T0=27239.542 s UT (07:33:59.542).
The burst light curve shows a single pulse with a duration of ~6 s.
As observed by Konus-Wind the burst
had a fluence of 4.90(-2.76, +0.26)x10^-6 erg/cm2,
and a 64-ms peak flux measured from T0-0.016 s
of 4.44(-2.65, +0.91)x10^-6 erg/cm2/s
(both in the 20 keV - 1 MeV energy range).
The time-integrated spectrum of the burst
(from T0 to T0+8.448 s) is well fitted
(in the 20 keV - 1 MeV range)
by a power law with exponential cutoff model:
dN/dE ~ E^(-alpha)*exp(-E*(2-alpha)/Ep)
with alpha = 1.36(-0.25, +0.21)
and Ep = 211(-48, +95) keV (chi2 = 58.9/60 dof).
All the quoted errors are at the 90% confidence level.
The Konus-Wind light curve of this GRB is available
at http://www.ioffe.rssi.ru/LEA/GRBs/GRB070917_T27239/
GCN Circular 6799
Subject
GRB 070917: pseudo-z= 2.40 from prompt emission spectrum
Date
2007-09-18T13:58:34Z (18 years ago)
From
Alexandre Pelangeon at LATT,OMP,Toulouse <alexandre.pelangeon@ast.obs-mip.fr>
A. Pelangeon & J-L. Atteia (LATT-OMP) report:
We have used the spectral parameters of the most intense
part of GRB 070917 provided by Golenetskii et al. (GCNC 6798)
to compute the spectral pseudo-redshift(**) of this burst
detected by SWIFT-BAT (Cummings et al., GCNC 6791).
We find a pseudo-redshift pz= 2.40 +/- 1.20
(**) cf. http://www.ast.obs-mip.fr/grb/pz
GCN Circular 6800
Subject
GRB 070917: P60 Observations
Date
2007-09-19T00:08:45Z (18 years ago)
From
S. Bradley Cenko at Caltech <cenko@srl.caltech.edu>
S. B. Cenko (Caltech) reports on behalf of a larger collaboration:
We have imaged the field of GRB070917 (Cummings et al., GCN 6791) with the
automated Palomar 60-inch telescope. Images were obtained in the Kron R
and Sloan i' filters beginning 2.65 minutes after the burst trigger under
poor seeing conditions.
Inside the XRT error circle (Evans et al., GCN 6796), we marginally detect
in both filters a single faint source not clearly visible in the DSS-II
plate at the location (J2000.0)
RA: 19:35:40.53
Dec: +02:24:40.4
Using several nearby stars from the USNO-B catalog for reference, and the
empirical filter transformations from Jordi, Grebel, and Ammon (A&A 460,
2006), we measure magnitudes of R ~ 22.0 mag, i' ~ 21.6 mag, with the
large uncertainties (~ 0.4 mag) due to both photometric calibration and
the faintness of object.
Given the faintness, we cannot determine at this time if this object is
variable. Furthermore, as it likely lies below the detection limit of the
DSS-II survey, further observations are required to establish if it is
indeed the optical afterglow of GRB 070917.
GCN Circular 6801
Subject
GRB070917: optical observations
Date
2007-09-19T18:25:37Z (18 years ago)
From
Alexei Pozanenko at IKI, Moscow <apozanen@iki.rssi.ru>
K. Antonyuk, V. Rumyantsev (CrAO), A. Pozanenko (IKI) report on behalf of
larger GRB follow-up collaboration:
We observed the error box of GRB070917 (Cummings et al., GCN 6743) with
AZT-11 telescope of CrAO on Sep. 17. Series of images were obtained between
(UT) 2007-09-17 18:58:08 and 19:25:37 in R filter. In a combined image of
6x300 s within the XRT error circle (Evans et al., GCN 6796) we do not
detect any new sources in comparison with DSS2 up to the limiting magnitude
(3 sigma) R=21.1. Photometry calibration is performed against USNO-A2.0. The
combined image can be found in
http://grb.rssi.ru/GRB070917/GRB070917_AZT-11.gif.
This message may be cited.
GCN Circular 6803
Subject
GRB070917: Confirmation of optical afterglow
Date
2007-09-19T19:12:30Z (18 years ago)
From
Johan U. Fynbo at U.Copenhagen <jfynbo@astro.ku.dk>
J.P.U. Fynbo, M.D. Stritzinger, C. Gall (DARK/NBI), A.O. Jaunsen (Univ.
Oslo), C.C. Thoene, D. Malesani, P. Vreeswijk, J. Hjorth (DARK/NBI), J.
Sollerman (DARK and Univ. Stockholm) report on behalf of a larger
collaboration.
We observed the optical afterglow of GRB 070917 (Cummings et al., GCN
6791; Cenko, GCN 6800) with the Nordic Optical Telescope. Observations
started on 2007 Sep. 17.89 UT (14 hr after the GRB) in the V, R and I
bands. We detect the candidate optical afterglow reported by Cenko (GCN
6800) in all three bands. Assuming R=18.1 for the star USNO0900_15777166
we derive an R-band magnitude of 23.1. Compared to the magnitudes reported
by Cenko (GCN 6800) the source appears to be fading and we hence confirm
this source as the likely optical afterglow of GRB 070917.
GCN Circular 6813
Subject
GRB 070917: Confirmation of the X-ray afterglow
Date
2007-09-21T14:12:52Z (18 years ago)
From
Kim Page at U.of Leicester <kpa@star.le.ac.uk>
K.L. Page (U. Leicester) and J.R. Cummings (NASA/UMBC) report on behalf of
the Swift-XRT team:
Additional Swift-XRT observations have been performed of the possible
X-ray afterglow of GRB 070917 (Evans et al., GCN Circ. 6796). Between
~3.5e4 and 3.5e5 seconds after the burst, the source has faded following a
power-law decay slope of alpha = 1.1 +/- 0.3, confirming that it is,
indeed, the afterglow. Using ~14 ks of data, we find a refined position of
RA, Dec = 293.91897, 2.41104 degrees, which is equivalent to:
RA(J2000) = 19 35 40.55
Dec(J2000)= +02 24 39.8
with an estimated uncertainty of 6.0 arcsec (radius, 90% containment
including boresight uncertainty). This source is 0.7" from the optical
counterpart discussed by Cenko (GCN Circ. 6800) and Fynbo et al. (GCN Circ
6803).
This circular is an official product of the Swift-XRT team.
GCN Circular 6817
Subject
GRB 070917: Suzaku/WAM observation of the prompt emission
Date
2007-09-23T14:17:44Z (18 years ago)
From
Makoto Tashiro at Saitama U/Swift <tashiro@phy.saitama-u.ac.jp>
GRB 070917: Suzaku WAM observation of the prompt emission
A. Endo, M. Tashiro, Y. Urata, K. Onda, M. Suzuki, N. Kodaka,
K. Morigami (Saitama U.), Y. Terada, T. Tamagawa (RIKEN),
M. Ohno, T. Uehara, T. Takahashi, Y. Fukazawa, C. Kira (Hiroshima U.),
K. Yamaoka, Y. E. Nakagawa, S. Sugita (Aoyama Gakuin U.),
T. Enoto, R. Miyawaki, K. Nakawaza, K. Makishima (Univ. of Tokyo),
E. Sonoda, M.Yamauchi, S. Maeno, H. Tanaka, R. Hara (Univ. of
Miyazaki),
M. Kokubun, M. Suzuki, T. Takahashi (ISAS/JAXA), S. Hong (Nihon U.),
on behalf of the Suzaku WAM team, report:
The long GRB 070917 (Swift/BAT trigger #291292 ; Cummings et al.,
GCN 6791) triggered the Suzaku Wide-band All-sky Monitor (WAM)
which covers an energy range of 50 keV - 5 MeV
at 2007-09-17 07:33:56.500 UT (=T0).
The observed light curve shows a single peak starting at T0+0s, ending
at T0+3s with a duration (T90) of about 2.5 seconds. The fluence in
100 - 1000 keV was 2.4 (+0.2, -0.2) * 10^(-6) erg/cm2. The 1-s peak flux
measured from T0+0s was 3.1 (+0.3, -0.3) photons/cm2/s in the
same energy range.
Preliminary result shows that the time-averaged spectrum from T0+0s to
T0+3s is well fitted by a single power-law with a photon index
of 1.6 (+0.2, -0.2) (chi2/d.o.f. = 9.6/11).
All the quoted errors are at statistical 90% confidence level,
in which the systematic uncertainties are not included.
The light curves for this burst are available at:
http://www.astro.isas.jaxa.jp/suzaku/HXD-WAM/WAM-GRB/grb/trig/grb_table.html