TITLE: GCN CIRCULAR NUMBER: 40055 SUBJECT: GRB 250330A Swift-BAT refined analysis DATE: 25/04/04 16:15:22 GMT FROM: Mike Moss at NASA GSFC mikejmoss3@gmail.com

H. A. Krimm (NSF), S. D. Barthelmy (GSFC), S. B. Cenko (GSFC), R. Gupta (GSFC), 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), T. Sakamoto (AGU) (i.e. the Swift-BAT team):

Using the data set from T-137 to T+963 sec from the recent telemetry downlink, we report further analysis of BAT GRB 250330A (trigger #1299776) (Cenko, et al., GCN Circ. 39938). The BAT ground-calculated position is RA, Dec = 252.685, -86.875 deg which is RA(J2000) = 16h 50m 44.5s Dec(J2000) = -86d 52' 29.6" with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment). The partial coding was 98%.

The mask-weighted light curve shows a single well defined fast-rise exponential- decay pulse shape. the T90 (15-350 keV) is 11.27 +- 2.53 sec (estimated error including systematics).

The time-averaged spectrum from T-0.16 to T+14.33 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.72 +- 0.10. The fluence in the 15-150 keV band is 9.2 +- 0.6 x 10^-07 erg/cm2. The 1-sec peak photon flux measured from T+0.26 sec in the 15-150 keV band is 4.0 +- 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/1299776

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