TITLE: GCN CIRCULAR NUMBER: 40633 SUBJECT: GRB 250605A: Swift detection of a burst DATE: 25/06/05 19:08:03 GMT FROM: K.L. Page at U Leicester klp5@leicester.ac.uk
R. Gupta (NASA GSFC), J. J. DeLaunay (PSU), S. Dichiara (PSU), C. Gronwall (PSU), N. J. Klingler (GSFC/UMBC/CRESSTII), H. A. Krimm (NSF), M. J. Moss (GSFC), K. L. Page (U Leicester), T. M. Parsotan (GSFC), M. H. Siegel (PSU) and M. A. Williams (PSU) report on behalf of the Neil Gehrels Swift Observatory Team:
At 18:52:31.27 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 250605A (trigger=1321323). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 166.977, -19.795 which is RA(J2000) = 11h 07m 54s Dec(J2000) = -19d 47' 42" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve shows a complex light curve with one strong pulse between T0-2 sec to T0+10 sec and a second dimmer but broad pulse between T0+40 sec to T0+100 sec. The peak count rate was 4,000 counts/sec (15-350 keV), at ~2 sec after the trigger.
The XRT began observing the field at 18:54:09.2 UT, 98.0 seconds after the BAT trigger. XRT found a bright, uncatalogued X-ray source located at RA, Dec 166.9571, -19.7882 which is equivalent to: RA(J2000) = 11h 07m 49.70s Dec(J2000) = -19d 47' 17.5" with an uncertainty of 5.5 arcseconds (radius, 90% containment). This location is 71 arcseconds from the BAT onboard position, within the BAT error circle. No event data are yet available to determine the column density using X-ray spectroscopy.
UVOT took a finding chart exposure of 144 seconds with the White filter starting 106 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 100% of the XRT error circle. The typical 3-sigma upper limit has been about 19.6 mag. 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 0.039.
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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