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GCN Circular 41730

Subject

GRB 250904A: Swift-BAT refined analysis

Event

GRB 250904A

Date

2025-09-05T21:28:22Z (4 days ago)

From

D. R. Sadaula at NASA GSFC <dev.r.sadaula@nasa.gov>

Via

Web form

D. M. Palmer (LANL), 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),
T. Parsotan (GSFC), D. Sadaula (GSFC/UMBC),
T. Sakamoto (AGU) (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 250904 A (trigger #1347179)
(Salvaggio, et al., GCN Circ. 41704Loading...
 
 ).  The BAT ground-calculated position is
RA, Dec = 84.377, 3.575 deg which is 
   RA(J2000)  =  05h 37m 30.5s 
   Dec(J2000) = +03d 34' 29.9" 
with an uncertainty of 1.0 arcmin (radius, sys+stat, 90% containment).
The partial coding was 100%.
 
The BAT light curve showed a complex structure with a duration of about 50 sec.
T90 (15-350 keV) is 37.11 +- 13.89 sec (estimated error including systematics).
 
The time-averaged spectrum from T-19.68 to T+54.44 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.40 +- 0.11.  The fluence in the 15-150 keV band is 1.7 +- 0.1 x 10^-06 erg/cm2.
The 1-sec peak photon flux measured from T+5.11 sec in the 15-150 keV band
is 1.1 +- 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/1347179