TITLE: GCN CIRCULAR NUMBER: 12088 SUBJECT: GRB 110625A: Swift detection of a burst DATE: 11/06/25 21:25:19 GMT FROM: Scott Barthelmy at NASA/GSFC K. L. Page (U Leicester), S. D. Barthelmy (GSFC), A. P. Beardmore (U Leicester), J. R. Cummings (NASA/UMBC), V. D'Elia (ASDC), S. T. Holland (CRESST/USRA/GSFC), F. E. Marshall (NASA/GSFC), C. Pagani (U Leicester), D. M. Palmer (LANL), P. Romano (INAF-IASFPA), C. J. Saxton (UCL-MSSL), M. H. Siegel (PSU), M. C. Stroh (PSU) and T. N. Ukwatta (MSU) report on behalf of the Swift Team: At 21:08:28 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 110625A (trigger=456073). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 286.750, +6.753, which is RA(J2000) = 19h 07m 00s Dec(J2000) = +06d 45' 10" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve shows several bright peaks with a total duration of about 60 sec. The peak count rate was ~20,000 counts/sec (15-350 keV), at ~13 sec after the trigger. The XRT began observing the field at 21:10:48.8 UT, 140.3 seconds after the BAT trigger. Using promptly downlinked data we find a bright, fading, uncatalogued X-ray source located at RA, Dec 286.73189, 6.75386 which is equivalent to: RA(J2000) = 19h 06m 55.65s Dec(J2000) = +06d 45' 13.9" with an uncertainty of 3.8 arcseconds (radius, 90% containment). This location is 64 arcseconds from the BAT onboard position, within the BAT error circle. This position may be improved as more data are received; the latest position is available at http://www.swift.ac.uk/sper. A power-law fit to a spectrum formed from promptly downlinked event data does not constrain the column density. The initial flux in the 2.5 s image was 1.72e-09 erg cm^-2 s^-1 (0.2-10 keV). UVOT took a finding chart exposure of 250 seconds with the U filter starting 205 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 19.2 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 18.0 mag. No correction has been made for the large, but uncertain extinction expected. Burst Advocate for this burst is K. L. Page (kpa AT star.le.ac.uk). 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/too.html.)