TITLE: GCN CIRCULAR NUMBER: 11790 SUBJECT: GRB 110315A: Swift detection of a burst DATE: 11/03/16 00:09:22 GMT FROM: Scott Barthelmy at NASA/GSFC A. Melandri (INAF-OAB), S. D. Barthelmy (GSFC), P. D'Avanzo (INAF-OAB), N. Gehrels (NASA/GSFC), J. M. Gelbord (PSU), C. Gronwall (PSU), S. T. Holland (CRESST/USRA/GSFC), E. A. Hoversten (PSU), J. A. Kennea (PSU), N. P. M. Kuin (UCL-MSSL), V. Mangano (INAF-IASFPA), R. Margutti (INAF-OAB), C. B. Markwardt (NASA/GSFC), F. E. Marshall (NASA/GSFC), C. J. Saxton (UCL-MSSL), B. Sbarufatti (INAF-OAB/IASFPA) and M. H. Siegel (PSU) report on behalf of the Swift Team: At 23:57:04 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 110315A (trigger=449399). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 279.191, +17.532 which is RA(J2000) = 18h 36m 46s Dec(J2000) = +17d 31' 56" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve shows 3 or 4 peaks with a total duration of about 20 sec. The peak count rate was ~1200 counts/sec (15-350 keV), at ~2 sec after the trigger. The XRT began observing the field at 23:58:49.1 UT, 104.6 seconds after the BAT trigger. XRT found a bright, uncatalogued X-ray source located at RA, Dec 279.1928, +17.5388 which is equivalent to: RA(J2000) = 18h 36m 46.27s Dec(J2000) = +17d 32' 19.6" with an uncertainty of 5.8 arcseconds (radius, 90% containment). This location is 25 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 150 seconds with the White filter starting 112 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 coverage of the XRT error circle by the 8'x8' region for the list of sources generated on-board is uncertain because the large number of sources filled the available telemetry. No correction has been made for the expected extinction corresponding to E(B-V) of 0.25. Burst Advocate for this burst is A. Melandri (andrea.melandri AT brera.inaf.it). 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.)