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GCN Circular 30536

Subject
GRB 210726A: Swift-BAT refined analysis
Date
2021-07-27T19:36:05Z (3 years ago)
From
Amy Lien at GSFC <amy.y.lien@nasa.gov>
D. M. Palmer (LANL), S. D. Barthelmy (GSFC),
M. G. Bernardini (INAF-OAB), H. A. Krimm (NSF),
S. Laha (GSFC/UMBC), A. Y. Lien (GSFC/UMBC),
C. B. Markwardt (GSFC), 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 210726A (trigger #1061687)
(Bernardini et al., GCN Circ. 30523).  The BAT ground-calculated position is
RA, Dec = 193.333, 19.211 deg which is
   RA(J2000)  =  12h 53m 19.9s
   Dec(J2000) = +19d 12' 38.9"
with an uncertainty of 2.6 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 100%.

The mask-weighted light curve shows a short spike that starts at ~T0,
peaks at ~T+0.2 s, and ends at ~T+0.4 s. Some tail emission from the
raw light curves was mentioned in the original circular (Bernardini et al.,
GCN Circ. 30523), and this potential weak tail can be seen in the 1-s
binned
light curve (15-350 keV) as well. However, image analyses from ~T+0.5 s
to ~T+2 s do not find any significant detections that are >~ 2 sigma.
Therefore, this signal is also consistent with noise fluctuation.
T90 (15-350 keV) is 0.39 +- 0.11 sec (estimated error including
systematics).

The time-averaged spectrum from T-0.00 to T+0.42 sec is best fit by
a simple power-law model.  The power law index of the time-averaged
spectrum is 1.54 +- 0.47.  The fluence in the 15-150 keV band is
4.5 +- 1.1 x 10^-8 erg/cm2. The 1-sec peak photon flux measured from
T-0.29 sec in the 15-150 keV band is 0.7 +- 0.3 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/1061687/BA/
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