TITLE: GCN CIRCULAR NUMBER: 40057 SUBJECT: GRB 250331C Swift-BAT refined analysis DATE: 25/04/04 16:17:44 GMT FROM: Mike Moss at NASA GSFC mikejmoss3@gmail.com
A. Y. Lien (U Tampa), S. D. Barthelmy (GSFC), S. B. Cenko (GSFC), R. Gupta (GSFC), H. A. Krimm (NSF), S. Laha (GSFC/UMBC), 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-239 to T+963 sec from the recent telemetry downlink, we report further analysis of BAT GRB 250331C (trigger #1299967) (Cenko, et al., GCN Circ. 39959). The BAT ground-calculated position is RA, Dec = 80.963, 33.068 deg which is RA(J2000) = 05h 23m 51.0s Dec(J2000) = +33d 04' 03.4" with an uncertainty of 2.0 arcmin, (radius, sys+stat, 90% containment). The partial coding was 100%.
The mask-weighted light curve shows a dim pulse of emission with some possible complex structure. The T90 (15-350 keV) is 70.10 +- 11.70 sec (estimated error including systematics).
The time-averaged spectrum from T-12.59 to T+66.67 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.88 +- 0.23. The fluence in the 15-150 keV band is 6.6 +- 1.0 x 10^-07 erg/cm2. The 1-sec peak photon flux measured from T-3.19 sec in the 15-150 keV band is 0.3 +- 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/1299967
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