TITLE: GCN CIRCULAR NUMBER: 39473 SUBJECT: GRB 250225B: Swift detection of a burst DATE: 25/02/25 20:00:29 GMT FROM: David Palmer at LANL palmer@lanl.gov
M. A. Williams (PSU), S. Dichiara (PSU), R. Gupta (NASA GSFC), H. A. Krimm (NSF), M. J. Moss (GSFC), K. L. Page (U Leicester) and D. M. Palmer (LANL) report on behalf of the Neil Gehrels Swift Observatory Team:
At 19:39:13 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 250225B (trigger=1291459). Swift could not slew immediately due to an observing constraint. The BAT on-board calculated location is RA, Dec 306.145, -41.484 which is RA(J2000) = 20h 24m 35s Dec(J2000) = -41d 29' 03" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a multiple-peaked structure (well-separated peaks at T+1, T+60, T+110) with a total duration of about 120 sec. The peak count rate was ~13000 counts/sec (15-350 keV), at ~1 sec after the trigger.
Due to a Moon observing constraint, Swift cannot slew to the BAT position until 05:11 UT on 2025 February 26. There will thus be no XRT or UVOT data for this trigger before this time.
We note the presence of the Emission-line Galaxy ESO 340-26 in the BAT error box. This is a bright (B=14.8, R=10.9) extended (1.4 arcmin) galaxy at z ~ 0.018 .
Burst Advocate for this burst is M. A. Williams (mjw6837 AT psu.edu). Please contact the BA by email if you require additional information regarding Swift followup of this burst. In extremely urgent cases, after trying the Burst Advocate, you can contact the Swift PI by phone (see Swift TOO web site for information: http://www.swift.psu.edu/)
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