TITLE:   GCN CIRCULAR
NUMBER:  45686
SUBJECT: GRB 260921A: Swift-BAT refined analysis
DATE:    26/09/22 01:58:07 GMT
FROM:    Amy <yarleen@gmail.com>

T. Parsotan (GSFC), S. D. Barthelmy (GSFC), R. Gupta (GSFC), H. A. Krimm
(NSF), S. Laha (GSFC/UMBC), A. Y. Lien (U Tampa), C. B. Markwardt (GSFC),
M. J. Moss (GSFC), K. L. Page (U Leicester), D. M. Palmer (LANL), D.
Sadaula (GSFC/UMBC), T. Sakamoto (AGU) (i.e. the Swift-BAT team):

Using the data set from T-61 to T+243 sec from the recent telemetry
downlink, we report further analysis of BAT GRB 260921A (trigger #1512356)
(Page et al., GCN Circ. 45676).  The BAT ground-calculated position is
RA, Dec = 145.376, 2.849 deg which is
   RA(J2000)  =  09h 41m 30.2s
   Dec(J2000) = +02d 50' 55.6"
with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 27%.

The mask-weighted light curve shows a single-pulse structure that starts at
~T-7 s, peaks at ~T0, and ends at ~T+7 s. T90 (15-350 keV) is 8.62 +- 1.44
sec (estimated error including systematics).

The time-averaged spectrum from T-6.88 to T+6.93 sec is best fit by a
simple power-law model.  The power law index of the time-averaged spectrum
is 1.29 +- 0.07.  The fluence in the 15-150 keV band is 3.4 +- 0.1 x 10^-06
erg/cm2. The 1-sec peak photon flux measured from T+0.13 sec in the 15-150
keV band is 7.5 +- 0.6 ph/cm2/sec.  All the quoted errors are at the 90%
confidence level.

The results of the batgrbproduct analysis are available at
https://swift.gsfc.nasa.gov/results/batgrbcat/BAT_refined_circular/1512356