GCN Circular 41868

T. Parsotan (GSFC), S. D. Barthelmy (GSFC), R. Caputo (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), D. M. Palmer (LANL), D. Sadaula
(GSFC/UMBC), T. Sakamoto (AGU) (i.e. the Swift-BAT team):

Using the data set from T-240 to T+962 sec from the recent telemetry
downlink, we report further analysis of BAT GRB 250917B (trigger #1350381)
(Caputo et al., GCN Circ. 41848
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 ).  The BAT ground-calculated position is
RA, Dec = 291.382, 11.117 deg which is
   RA(J2000)  =  19h 25m 31.8s
   Dec(J2000) = +11d 06' 59.9"
with an uncertainty of 1.4 arcmin, (radius, sys+stat, 90% containment). The
partial coding was 48%.

The mask-weighted light curve shows a single FRED-like structure that
starts at ~T-0.1, peaks at ~T0, and ends at ~T+0.4. T90 (15-350 keV) is
0.29 +- 0.08 sec (estimated error including systematics).

The time-averaged spectrum from T+0.00 to T+0.37 sec is best fit by a
simple power-law model.  The power law index of the time-averaged spectrum
is 1.66 +- 0.17.  The fluence in the 15-150 keV band is 1.7 +- 0.2 x 10^-07
erg/cm2. The 1-sec peak photon flux measured from T-0.31 sec in the 15-150
keV band is 2.4 +- 0.3 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/1350381