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GCN Circular 21912

Subject

GRB 170921A: Swift-BAT refined analysis

Date

2017-09-22T14:27:15Z (7 years ago)

From

Amy Lien at GSFC <amy.y.lien@nasa.gov>

T. Sakamoto (AGU), S. D. Barthelmy (GSFC),
J. R. Cummings (CPI), A. D'Ai (INAF-IASFPA)
H. A. Krimm (NSF/USRA), A. Y. Lien (GSFC/UMBC),
C. B. Markwardt (GSFC), D. M. Palmer (LANL),
M. Stamatikos (OSU), T. N. Ukwatta (LANL)
(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 GRB 170921A (trigger #773509)
(D'Ai et al., GCN Circ. 21901Not found
 
 
).  The BAT ground-calculated position is
RA, Dec = 26.840, 30.880 deg which is
  RA(J2000)  =  01h 47m 21.6s
  Dec(J2000) = +30d 52' 47.1"
with an uncertainty of 1.8 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 86%.

The mask-weighted light curve shows a single-peaked structure that starts at
~T-22 s, peaks at ~T+3 s, and ends at ~T+13 s. T90 (15-350 keV) is
28.9 +- 6.0 sec (estimated error including systematics).

The time-averaged spectrum from T-21.82 to T+13.00 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.76 +- 0.17.  The fluence in the 15-150 keV band is 6.7 +- 0.8 x 10^-7 erg/cm2.
The 1-sec peak photon flux measured from T+2.74 sec in the 15-150 keV band
is 0.8 +- 0.2 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/773509/BA/