GCN Circular 42006

Subject

GRB 250925A: Swift-BAT refined analysis

Event

GRB 250925A

Date

2025-09-26T15:51:01Z (6 days ago)

From

Hans Krimm at NSF/NASA-GSFC <hkrimm@nsf.gov>

Via

S. D. Barthelmy (GSFC), S. Dichiara (PSU), 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),
T. Parsotan (GSFC), 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 250925A (trigger #1352124)
(Dichiara, et al., GCN Circ. 41985Loading...
 
 ).  The BAT ground-calculated position is
RA, Dec = 341.207, 46.549 deg which is
   RA(J2000)  =  22h 44m 49.7s
   Dec(J2000) = +46d 32' 57.0"
with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 76%.

The mask-weighted light curve shows a broad, multi-peaked structure starting at ~T-25 sec and decaying to background by T+50 sec. T90 (15-350 keV) is 64.51 +- 6.59 sec (estimated error including systematics).

The time-averaged spectrum from T-23.52 to T+64.42 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.87 +- 0.09.  The fluence in the 15-150 keV band is 2.7 +- 0.1 x 10^-6 erg/cm2.
The 1-sec peak photon flux measured from T+0.19 sec in the 15-150 keV band
is 1.2 +- 0.2 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/1352124