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GCN Circular 21796

Subject

GRB 170903A: Swift-BAT refined analysis

Date

2017-09-03T17:30:06Z (7 years ago)

From

Scott Barthelmy at NASA/GSFC <scott@lheamail.gsfc.nasa.gov>

S. D. Barthelmy (GSFC), J. R. Cummings (CPI), H. A. Krimm (NSF/USRA),
A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC), D. M. Palmer (LANL),
T. Sakamoto (AGU), M. Stamatikos (OSU), T. N. Ukwatta (LANL)
(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 170903A (trigger #770528)
(Markwardt, et al., GCN Circ. 21793Not found
 
 
).  The BAT ground-calculated position is
RA, Dec = 254.532, 34.985 deg, which is 
   RA(J2000)  =  16h 58m 07.7s 
   Dec(J2000) = +34d 59' 07.5" 
with an uncertainty of 1.3 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 30%.
 
The mask-weighted light curve shows two slightly overlapping peaks starting
at ~T-5 sec, with a maximum at ~T+1 sec, and returning to baseline at ~T+70 sec.
T90 (15-350 keV) is 29.2 +- 4.4 sec (estimated error including systematics).
 
The time-averaged spectrum from T-10.00 to T+25.70 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.94 +- 0.12.  The fluence in the 15-150 keV band is 2.4 +- 0.2 x 10^-6 erg/cm2.
The 1-sec peak photon flux measured from T+0.58 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/770528/BA/