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GCN Circular 29939

Subject
GRB 210504A: Swift-BAT refined analysis
Date
2021-05-05T02:27:49Z (3 years ago)
From
Amy Lien at GSFC <amy.y.lien@nasa.gov>
S. Laha (GSFC/UMBC), S. D. Barthelmy (GSFC),
A. P. Beardmore (U Leicester), J. R. Cummings (CPI),
H. A. Krimm (NSF), 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-239 to T+963 sec from the recent telemetry
downlink, we report further analysis of BAT GRB 210504A (trigger #1046782)
(Beardmore et al., GCN Circ. 29929).  The BAT ground-calculated position is
RA, Dec = 222.379, -30.557 deg which is
   RA(J2000)  =  14h 49m 31.0s
   Dec(J2000) = -30d 33' 23.5"
with an uncertainty of 2.1 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 53%.

The mask-weighted light curve shows several overlapping pulses
that start at ~T-30 s and end at ~T+150 s. There might be additional
burst emission before the GRB came into the BAT FOV at ~T-43 s.
T90 (15-350 keV) is 135.06 +- 9.57 sec (estimated error including
systematics).

The time-averaged spectrum from T-27.55 to T+134.76 sec is best fit
by a simple power-law model.  The power law index of the time-averaged
spectrum is 1.64 +- 0.13.  The fluence in the 15-150 keV band is
2.7 +- 0.2 x 10^-6 erg/cm2. The 1-sec peak photon flux measured from
T+87.68 sec in the 15-150 keV band is 0.9 +- 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/1046782/BA/
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