TITLE: GCN CIRCULAR NUMBER: 37355 SUBJECT: GRB 240825A: Swift-BAT refined analysis DATE: 24/08/30 23:32:53 GMT FROM: Amy yarleen@gmail.com

M. J. Moss (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), 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-240 to T+800 sec from the recent telemetry downlink, we report further analysis of BAT GRB 240825A (trigger #1250617) (Gupta et al., GCN Circ. 37274). The BAT ground-calculated position is RA, Dec = 344.570, 1.019 deg which is RA(J2000) = 22h 58m 16.9s Dec(J2000) = +01d 01' 08.9" with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment). The partial coding was 53%.

The mask-weighted light curve shows a very bright FRED-like pulse that starts at ~T0 and peaks at ~T+1.8 s. In addition, there are some secondary pulses on top of the main FRED-like structure. The main structure ends at ~T+10 s, and there is a long tail emission that lasts till ~T+300 s. T90 (15-350 keV) is 57.20 +- 8.57 sec (estimated error including systematics).

The time-averaged spectrum from T-0.04 to T+216.76 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.20 +- 0.03. The fluence in the 15-150 keV band is 2.5 +- 0.04 x 10^-05 erg/cm2. The 1-sec peak photon flux measured from T+1.44 sec in the 15-150 keV band is 100.0 +- 1.7 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/1250617

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