GRB 080916A
GCN Circular 8241
Subject
GRB 080916A: Enhanced Swift-XRT position
Date
2008-09-16T15:21:27Z (17 years ago)
From
Phil Evans at U of Leicester <pae9@star.le.ac.uk>
P.A. Evans, M.R. Goad, J.P. Osborne and A.P. Beardmore (U. Leicester)
report on behalf of the Swift-XRT team.
Using 2559 s of XRT Photon Counting mode data and 3 UVOT
images for GRB 080916A, 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 = 336.27682, -57.02271 which is equivalent
to:
RA (J2000): 22h 25m 6.44s
Dec (J2000): -57d 01' 21.7"
with an uncertainty of 1.8 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
http://www.swift.ac.uk/xrt_positions/Goad.pdf), the current algorithm is an
extension of this method.
This circular was automatically generated, and is an official product of the
Swift-XRT team.
GCN Circular 8243
Subject
GRB 080916A, Swift-BAT refined analysis
Date
2008-09-16T17:06:23Z (17 years ago)
From
Scott Barthelmy at NASA/GSFC <scott@lheamail.gsfc.nasa.gov>
W. Baumgartner (GSFC/UMBC), S. D. Barthelmy (GSFC), J. Cummings (GSFC/UMBC),
E. Fenimore (LANL), N. Gehrels (GSFC), H. Krimm (GSFC/USRA),
C. Markwardt (GSFC/UMD), K. McLean (GSFC/UMD), D. Palmer (LANL),
A. Parsons (GSFC), T. Sakamoto (GSFC/UMBC), G. Sato (ISAS),
M. Stamatikos (GSFC/ORAU), J. Tueller (GSFC), T. Ukwatta (GWU),
H. Ziaeepour (UCL-MSSL)
(i.e. the Swift-BAT team):
Using the data set from T-240 to T+962 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 080916A (trigger #324895)
(Ziaeepour, et al., GCN Circ. 8237). The BAT ground-calculated position is
RA, Dec = 336.289, -57.026 deg, which is
RA(J2000) = 22h 25m 09.3s
Dec(J2000) = -57d 01' 33.7"
with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 82%.
The mask-weighted light curve shows two overlapping FRED peaks
starting at ~T-3 sec and ending at ~T+100 sec.
T90 (15-350 keV) is 60 +- 7 sec (estimated error including systematics).
The time-averaged spectrum from T-2.4 to T+88.6 sec is best fit by a power law
with an exponential cutoff. This fit gives a photon index 1.17 +- 0.21,
and Epeak of 94.6 +- 23.0 keV (chi squared 48.0 for 56 d.o.f.). For this
model the total fluence in the 15-150 keV band is 4.0 +- 0.1 x 10^-6 erg/cm2
and the 1-sec peak flux measured from T+1.25 sec in the 15-150 keV band is
2.7 +- 0.2 ph/cm2/sec. A fit to a simple power law gives a photon index
of 1.63 +- 0.05 (chi squared 64.5 for 57 d.o.f.). 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/324895/BA/
GCN Circular 8244
Subject
GRB 080916A: Swift XRT refined analysis
Date
2008-09-16T17:19:57Z (17 years ago)
From
Rhaana Starling at U of Leicester <rlcs1@star.le.ac.uk>
R.L.C. Starling (U. Leicester) and H. Ziaeepour (MSSL-UCL) report on
behalf of the Swift-XRT team:
We have analysed the first two orbits of Swift XRT data for GRB 080916A
(Ziaeepour et al., GCN Circ. 8237) from T0+70 s to T0+7440 s with total
exposure time 3.4 ks. The enhanced X-ray position is given in Evans et
al., GCN Circ. 8241.
The light curve can be represented by a 5-segment broken power law with an
initial decay alpha1=1.3+0.4/-0.6 breaking at Tbk1=102+4/-6 s to a steep
decay of alpha2=3.5+/-0.3 until Tbk2=190+25/-13 s. The light curve then
flattens to alpha3=1.07+0.06/-0.3 and breaks at Tbk3=690+150/-140 s to a
further steep decay of alpha4=2.9+2/-0.8. From Tbk4=1270+240/-220 s the
decay becomes shallow again with alpha5=0.3+/-0.2.
The spectrum from 3.2 ks of Photon Counting mode data can be fit with an
absorbed power law with photon index Gamma=2.1+/-0.2 and intrinsic
absorption (in excess of the Galactic value of 1.8e20 cm-2) of
nH=(2.6+0.7/-0.6)e21 cm-2. This is consistent with the spectrum formed
from the initial 170 s of Windowed Timing mode data. The observed
(unabsorbed) count rate to flux conversion is 1 count/s = 4.0e-11
(6.8e-11) erg/cm2/s.
The predicted count rate at T+24hr would be approximately 0.1 count/s if
the decay continues on the current plateau-like phase.
This circular is an official product of the Swift-XRT team.
GCN Circular 8249
Subject
GRB080916A: Refined Swift/UVOT Observations
Date
2008-09-16T19:58:10Z (17 years ago)
From
Samantha Oates at MSSL <sro@mssl.ucl.ac.uk>
S. R. Oates (UCL-MSSL) and H. Ziaeepour (UCL-MSSL) report on
behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of
GRB 080916A, 78s after the BAT trigger (Ziaeepour et al., GCN 8237).
We detect the afterglow in all of the UVOT filters at the position:
RA(J2000.0) = 22:25:06.20
DEC(J2000.0) = -57:01:22.9
with an estimated uncertainty of 0.5 arcsec (radius, 90% confidence).
This position is consistent with the UVOT enhanced XRT position (Evans et
al., GCN 8241) and the REM position (Fugazza et al., GCN 8238).
UVOT magnitudes are reported below for the finding charts (fc) and images:
Filter Tstart(s) Tstop Expo(s) Magnitude/3sigUL
-----------------------------------------------------
white (fc) 78 178 98 18.33 +/- 0.06
white 872 972 98 18.47 +/- 0.06
v (fc) 182 582 393 17.55 +/- 0.06
v 978 1378 393 18.39 +/- 0.11
b 1458 1477 19 18.90 +/- 0.35
u 538 658 19 17.53 +/- 0.19
w1 613 633 19 18.25 +/- 0.39
m2 741 1565 39 18.42 +/- 0.40
w2 692 864 39 18.75 +/- 0.37
-----------------------------------------------------
These magnitudes are not corrected for the Galactic extinction
corresponding to a reddening of E{B-V} = 0.02 mag (Schlegel et al.
1998). The photometry is on the UVOT flight system described in Poole
et al. (2008,MNRAS,383,627).
GCN Circular 8254
Subject
GRB080916A: Spectroscopic redshift
Date
2008-09-17T07:35:16Z (17 years ago)
From
Johan U. Fynbo at U.Copenhagen <jfynbo@astro.ku.dk>
J. P. U. Fynbo, D. Malesani, J. Hjorth, J. Sollerman, C. C. Thoene (DARK),
report on behalf of a larger collaboration.
We observed the field of GRB 080916A (Ziaeepour et al., GCN 8237) with the
ESO VLT equipped with FORS1. Observations started on 2008 Sep 17.097 UT,
17.1 hr after the burst, for a total exposure time of 1 hr with the 300V
grism. Based on MgII absorption and emission lines from [OII] and [OIII]
we infer a redshift for GRB080916A of z=0.689 (based a preliminary
wavelength calibration).
We acknowledge excellent support from the observing staff at
Paranal, in particular Dominique Naef, Heidi Korhonen and Chris Lidman.
GCN Circular 8259
Subject
Konus-Wind observation of GRB 080916A
Date
2008-09-17T14:31:01Z (17 years ago)
From
Valentin Pal'shin at Ioffe Inst <val@mail.ioffe.ru>
S. Golenetskii, R. Aptekar, E. Mazets, V. Pal'shin,
D. Frederiks, P. Oleynik, D. Svinkin, M. Ulanov
and T. Cline, on behalf of the Konus-Wind team report:
The long GRB 080916A (Swift-BAT trigger # 324895:
Ziaeepour et al., GCN 8237, Baumgartner et al. 8243) triggered
Konus-Wind at T0=35121.715 s UT (09:45:21.715).
The burst light curve shows a single pulse with a duration of ~40 s.
As observed by Konus-Wind the burst
had a fluence of 5.54(-0.66, +0.79)x10^-6 erg/cm2,
and a 256-ms peak flux measured from T0+1.024 s
of 1.05(-0.40, +0.41)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+33.024 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 = -1.00(-0.32, +0.38),
and Ep = 129(-21, +33) keV (chi2 = 32.0/51 dof).
Fitting by GRBM (Band) model yields only an upper limit on
the high energy photon index: beta < -2.43.
All the quoted errors are at the 90% confidence level.
Assuming z = 0.689 (Fynbo et al., GCN 8254) and a standard
cosmology model with H_0 = 70 km/s/Mpc, Omega_M = 0.27, Omega_\Lambda =
0.73, the isotropic energy release E_iso ~7x10^51 erg, the peak
luminosity (L_iso)_max ~ 2x10^51 erg/s, and Ep_rest ~220 keV.
The Konus-Wind light curve of this GRB is available
at http://www.ioffe.rssi.ru/LEA/GRBs/GRB080916_T35121/
GCN Circular 8263
Subject
GRB 080916A: Fermi GBM detection
Date
2008-09-17T22:39:42Z (17 years ago)
From
Elisabetta Bissaldi at MPE <ebs@mpe.mpg.de>
E. Bissaldi (MPE), S. McBreen (MPE),
C.A. Wilson-Hodge (NASA/MSFC) and A. von Kienlin (MPE)
report on behalf of the Fermi GBM Team:
"At 09:45:18 UT on 16 September 2008, the Fermi Gamma-ray Burst Monitor
triggered and located GRB 080916A (trigger 243251119 / 080916406), which
was also detected by Swift (Ziaeepour et al., GCN 8237) and
Konus-Wind (Golenetskii et al., GCN 8259). The on-ground
calculated location, using the Fermi GBM trigger data, is
RA = 331.5, Dec = -58.1 (equivalent to J2000
22h 06m, -58d 06'), with a statistical uncertainty of 3.2 degrees
(radius, 1-sigma containment; there is additionally a systematic
error which is currently estimated to be 2 to 3 degrees).
This position is 2.8 deg from the Swift refined position
(Evans et al., GCN 8241). The angle from the Fermi LAT boresight
to the Swift position is 76 degrees.
This long GRB consists of several peaks, with the brightest one
lasting from T0 to T0+13 s and a second peak from T0+13 s to T0+24 s
followed by weaker emission.
T90 (25-1000 keV) is about 60 sec, in agreement with
the Swift-BAT refined analysis (Baumgartner et al., GCN 8243),
and T50 (25-1000 keV) is about 25 s.
The time-averaged spectrum from T0 to T0+58 sec is
adequately fit by a power law function with an exponential
high energy cutoff. The power law index is -0.9 +/-0.1 and
the cutoff energy, parameterized as Epeak, is 109 +/- 9 keV.
The fluence (25-1000 keV) is 1.5 (+/- 0.5)E-05 erg/cm2
and the peak flux (25-1000 keV) on the 1 s timescale
is 4.5 (+/- 0.7) ph/cm2/s.
The spectral analysis results presented above are preliminary;
final results will be published in the Fermi GBM GRB Catalog."
GCN Circular 8264
Subject
GRB 080916A: Rapid PROMPT Observations
Date
2008-09-17T22:57:02Z (17 years ago)
From
Rebecca Holmes at U.North Carolina <rholmes@physics.unc.edu>
R. Holmes, M. Schubel, J. Haislip, D. Reichart, M. Nysewander, A.
LaCluyze, K. Ivarsen, J. A. Crain, A. Foster, T. Brennan, and A. Trotter
report:
Skynet observed the localization of GRB 080916A (Ziaeepour et al., GCN
8237) with four of the 16" PROMPT telescopes at CTIO beginning 56
seconds after the trigger in UBVRI.
We detect the afterglow (Fugazza et al., GCN 8238) in I. At 56 seconds
after the burst we measure I ~ 17.7 mag (calibrated to 5 USNO B1 stars).
GCN Circular 8266
Subject
GRB 080916A: GROND lightcurve
Date
2008-09-18T11:23:16Z (17 years ago)
From
Andrea Rossi at TLS Tautenburg <rossi@tls-tautenburg.de>
A. Rossi (Tautenburg Obs.),T. Kruehler, J. Greiner, A. Yoldas, C. Clemens,
R. Filgas (all MPE Garching), A. Kupcu Yoldas (ESO) and
G. Szokoly (Eoetvoes Univ.,Budapest) report on behalf of the GROND team:
GROND (Greiner et al. 2008, PASP 120, 405), mounted at the 2.2m ESO/MPI
telescope at La Silla Observatory (Chile), started observations of the
field of GRB 080916A (Ziaeepour et al. GCN #8237) in g'r'i'z'JHK at
23:57:34 UT on 2008-09-16, 14 hours after the burst trigger.
We clearly detect the optical afterglow detected by UVOT (Ziaeepour
et al. GCN #8237) and REM telescope (Fugazza et al. GCN #8238).
Observations continued for 60 min and were repeated at the mid-time
06:40 UT for total 60 min.
Calibrating the field on USNO-B1 stars, we derive the following
r band magnitudes, not corrected for the Galactic foreground
extinction corresponding to a reddening of E_(B-V)=0.019 mag
(Schlegel et al. 1998):
midtime(s) r er
52239 21.8 0.03
54054 21.9 0.04
74076 22.1 0.07
76260 22.3 0.07
The total r band light curve is well fitted by power law with index
of 0.81+- 0.13. Assuming the optical light curve continues
the decline with the same power law index, we predict r'
band magnitudes 23.4 at 3 days after the burst.
GCN Circular 8284
Subject
GRB080916A: Suzaku WAM observation of the prompt emission
Date
2008-09-23T14:59:42Z (17 years ago)
From
Kazutaka Yamaoka at Aoyama Gakuin U <yamaoka@phys.aoyama.ac.jp>
M. Suzuki, M. Kokubun, M. Ohno, T. Takahashi (ISAS/JAXA),
K. Yamaoka, S. Sugita (Aoyama Gakuin U.), Y.E. Nakagawa, T. Tamagawa
(RIKEN), T. Uehara, T. Takahashi, Y. Fukazawa, C. Kira, Y. Hanabata
(Hiroshima U.), M. Tashiro, Y. Terada, Y. Urata, A. Endo, K. Onda,
N. Kodaka, K. Morigami, T. Sugasahara, W. Iwakiri (Saitama U.),
T. Enoto, K. Nakazawa, K. Makishima (Univ. of Tokyo), E. Sonoda,
M. Yamauchi, H. Tanaka, R. Hara, N. Ohmori (Univ. of Miyazaki),
S. Hong (Nihon U.), on behalf of the Suzaku WAM team, report:
The long GRB080916A (Swift/BAT trigger #324895; Ziaeepour et al.,
GCN 8237) was detected by the Suzaku Wide-band All-sky Monitor (WAM)
which covers an energy range of 50 keV - 5 MeV at 09:45:19.970 UT (=T0).
The observed light curve shows a single peak at T0+0 s, followed by a second
soft peak at ~T0+16 s with a total duration (T90) of about 20 seconds.
The fluence in 100 - 500 keV was (2.57 +/- 0.32)x10^-6 erg/cm^2.
The 1-s peak flux measured from T0+0 s was
1.54 (-0.12, +0.25) photons/cm^2/s in the same energy range.
Preliminary result shows that the time-averaged spectrum from T0-5s to
T0+10s is fit by a single power-law with a photon index of
1.58 +/- 0.29 (chi^2/d.o.f = 13.1/12) in 100 - 500 keV.
All the quoted errors are at statistical 90% confidence level, in which
the systematic uncertainties are not included.
The light curves with 1/64 sec time resolution for this burst are now
available at:
http://www.astro.isas.jaxa.jp/suzaku/HXD-WAM/WAM-GRB/grb/trig/grb_table.html