TITLE: GCN CIRCULAR NUMBER: 14293 SUBJECT: GRB 130313A: Swift detection of a short burst DATE: 13/03/13 16:36:56 GMT FROM: Scott Barthelmy at NASA/GSFC B.P. Gompertz (U Leicester), S. D. Barthelmy (GSFC), A. P. Beardmore (U Leicester), D. N. Burrows (PSU), V. D'Elia (ASDC), S. T. Holland (STScI), C. B. Markwardt (NASA/GSFC), F. E. Marshall (NASA/GSFC), K. L. Page (U Leicester), M. H. Siegel (PSU), R. L. C. Starling (U Leicester), C. A. Swenson (PSU) and E. Troja (NASA/GSFC/UMCP) report on behalf of the Swift Team: At 16:08:11 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 130313A (trigger=550906). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 236.423, -0.362 which is RA(J2000) = 15h 45m 42s Dec(J2000) = -00d 21' 41" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve shows a single spike with a duration of about 0.2 sec. The peak count rate was ~2000 counts/sec (15-350 keV), at ~0 sec after the trigger. The XRT began observing the field at 16:09:29.2 UT, 78.1 seconds after the BAT trigger. No source was detected in 737 s of promptly downlinked data, which covered 93% of the BAT error circle. We are waiting for the full dataset to detect and localise the XRT counterpart. UVOT took a finding chart exposure of 150 seconds with the White filter starting 81 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 25% of the BAT 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 BAT 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 0.10. Burst Advocate for this burst is B.P. Gompertz (bpg6 AT 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.)