TITLE: GCN CIRCULAR NUMBER: 40357 SUBJECT: GRB 250504A: Swift-BAT refined analysis DATE: 25/05/06 02:54:01 GMT FROM: Mike Moss at NASA GSFC mikejmoss3@gmail.com
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 250504A (trigger #1310284) (Moss, et al., GCN Circ. 40343). The BAT ground-calculated position is RA, Dec = 269.605, -40.345 deg which is RA(J2000) = 17h 58m 25.3s Dec(J2000) = -40d 20' 41.8" with an uncertainty of 1.1 arcmin, (radius, sys+stat, 90% containment). The partial coding was 98%.
The mask-weighted light curve shows a complex light curve with several pulses. T90 (15-350 keV) is 52.39 +- 2.31 sec (estimated error including systematics).
The time-averaged spectrum from T-2.96 to T+55.10 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.27 +- 0.08. The fluence in the 15-150 keV band is 2.3 +- 0.1 x 10^-06 erg/cm2. The 1-sec peak photon flux measured from T+7.70 sec in the 15-150 keV band is 1.6 +- 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/1310284
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