TITLE: GCN CIRCULAR NUMBER: 41252 SUBJECT: GRB 250805A: Swift-BAT refined analysis DATE: 25/08/06 19:09:40 GMT FROM: Mike Moss at NASA GSFC mikejmoss3@gmail.com

T. Sakamoto (AGU), E. Ambrosi (INAF-IASFPA), 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), T. Parsotan (GSFC), D. Sadaula (GSFC/UMBC) (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 250805A (trigger #1339848) (Ambrosi, et al., GCN Circ. 41233). The BAT ground-calculated position is RA, Dec = 24.124, -81.400 deg which is RA(J2000) = 01h 36m 29.8s Dec(J2000) = -81d 23' 59.0" with an uncertainty of 1.4 arcmin, (radius, sys+stat, 90% containment). The partial coding was 65%.

The mask-weighted light curve displays a main emission period between T0-25 sec and T0+30 sec composed of multiple pulses with the strongest pulse beginning at T0. There is dim but significant emission beginning at T0-60 sec. The T90 (15-350 keV) is 79.37 +- 11.98 sec (estimated error including systematics).

The time-averaged spectrum from T-60.66 to T+36.25 sec is best fit by a power law with an exponential cutoff. This fit gives a photon index 0.58 +- 0.53, and Epeak of 68.0 +- 15.8 keV (chi squared 54.47 for 56 d.o.f.). For this model the total fluence in the 15-150 keV band is 2.2 +- 0.2 x 10^-06 erg/cm2 and the 1-sec peak flux measured from T+0.46 sec in the 15-150 keV band is 1.7 +- 0.2 ph/cm2/sec. A fit to a simple power law gives a photon index of 1.59 +- 0.11 (chi squared 67.84 for 57 d.o.f.). 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/1339848

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