TITLE: GCN CIRCULAR NUMBER: 40456 SUBJECT: GRB 250509A: Swift-BAT refined analysis DATE: 25/05/14 02:57:21 GMT FROM: Rahul Gupta at NASA GSFC rahul.gupta@nasa.gov
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), D. M. Palmer (LANL), D. Sadaula (GSFC/UMBC), T. Sakamoto (AGU), M. H. Siegel (PSU) (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 250509A (trigger #1311764) (Siegel, et al., GCN Circ. 40407). The BAT ground-calculated position is RA, Dec = 46.451, -38.854 deg which is RA(J2000) = 03h 05m 48.3s Dec(J2000) = -38d 51' 15.1" with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment). The partial coding was 96%.
The mask-weighted BAT light curve shows a sharp rise and exponential decay profile. T90 (15-350 keV) is 55.43 +- 10.47 sec (estimated error including systematics).
The time-averaged spectrum from T-2.85 to T+71.46 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.54 +- 0.08. The fluence in the 15-150 keV band is 2.4 +- 0.1 x 10^-06 erg/cm2. The 1-sec peak photon flux measured from T+0.42 sec in the 15-150 keV band is 1.9 +- 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/1311764
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