TITLE: GCN CIRCULAR NUMBER: 39835 SUBJECT: GRB 250322A: Swift detection of a short burst DATE: 25/03/22 16:26:08 GMT FROM: David Palmer at LANL palmer@lanl.gov
R. Gupta (NASA GSFC), R. Brivio (INAF-OAB), M. Ferro (INAF-OAB), J. A. Kennea (PSU), H. A. Krimm (NSF), M. J. Moss (GSFC), K. L. Page (U Leicester), D. M. Palmer (LANL), C. Salvaggio (INAF-OAB), T. Sbarrato (INAF-OAB), M. H. Siegel (PSU) and M. A. Williams (PSU) report on behalf of the Neil Gehrels Swift Observatory Team:
At 16:06:12 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 250322A (trigger=1297832). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 106.734, +7.199 which is RA(J2000) = 07h 06m 56s Dec(J2000) = +07d 11' 56" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a complex structure with a duration of about 1 sec. The peak count rate was ~10,000 counts/sec (15-350 keV), at ~0 sec after the trigger.
The XRT began observing the field at 16:07:25.4 UT, 73 seconds after the BAT trigger. Using promptly downlinked data we find an uncatalogued X-ray source with an enhanced position: RA, Dec 106.76025, 7.19285 which is equivalent to: RA(J2000) = 07h 07m 02.46s Dec(J2000) = +07d 11' 34.2" with an uncertainty of 1.9 arcseconds (radius, 90% containment). This position may be improved as more data are received; the latest position is available at https://www.swift.ac.uk/sper.
A power-law fit to a spectrum formed from promptly downlinked event data gives a column density consistent with the Galactic value of 2.70 x 10^21 cm^-2 (Willingale et al. 2013).
UVOT took a finding chart exposure of 150 seconds with the White filter starting 76 seconds after the BAT trigger. No credible afterglow candidate has been found in the initial data products. The 2.7'x2.7' sub-image covers none of the XRT error circle. The 8'x8' region for the list of sources generated on-board covers 100% of the XRT error circle. The list of sources is typically complete to about 18 mag. No correction has been made for the expected extinction corresponding to E(B-V) of 0.154.
Burst Advocate for this burst is R. Gupta (rahulbhu.c157 AT gmail.com). 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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