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GCN Circular 41081

Subject

GRB 250628A: Swift-BAT refined analysis

Event

GRB 250628A

Date

2025-07-13T20:59:21Z (2 days ago)

From

Takanori Sakamoto at AGU <tsakamoto@phys.aoyama.ac.jp>

Via

Web form

C. B. Markwardt (GSFC), S. D. Barthelmy (GSFC), M. Ferro (INAF-OAB),
R. Gupta (GSFC), H. A. Krimm (NSF), S. Laha (GSFC/UMBC),
A. Y. Lien (U Tampa), 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-240 to T+963 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 250628A (trigger #1328546)
(Ferro, et al., GCN Circ. 40853Loading...
 
 ).  The BAT ground-calculated position is
RA, Dec = 38.539, -38.082 deg which is
   RA(J2000)  =  02h 34m 09.3s
   Dec(J2000) = -38d 04' 54.3"
with an uncertainty of 1.5 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 51%.

The mask-weighted light curve shows a double-peak structure that starts at
~T-9 s, peaks at ~T+1 s, and ends at ~T+70 s.
T90 (15-350 keV) is 64 +- 11 sec (estimated error including systematics).

The time-averaged spectrum from T-9.42 to T+68.56 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.99 +- 0.12.  The fluence in the 15-150 keV band is 1.9 +- 0.1 x 10^-6 erg/cm2.
The 1-sec peak photon flux measured from T-0.10 sec in the 15-150 keV band
is 1.2 +- 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/1328546