TITLE: GCN CIRCULAR NUMBER: 17573 SUBJECT: GRB 150314A: Swift detection of a bright burst DATE: 15/03/14 05:15:27 GMT FROM: David Palmer at LANL L. M. Z. Hagen (PSU), S. D. Barthelmy (GSFC), J. A. Kennea (PSU), A. Y. Lien (GSFC/UMBC), F. E. Marshall (NASA/GSFC), D. M. Palmer (LANL) and B. Sbarufatti (INAF-OAB/PSU) report on behalf of the Swift Team: At 04:55:16 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 150314A (trigger=634795). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 126.659d, +63.833d which is RA(J2000) = 08h 26m 38s Dec(J2000) = +63d 50' 00" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a single complex peak structure with a duration of about 15 sec. The peak count rate was ~45000 counts/sec (15-350 keV), at ~1 sec after the trigger. The XRT began observing the field at 04:56:17.9 UT, 85.1 seconds after the BAT trigger. XRT found a bright, uncatalogued X-ray source located at RA, Dec 126.6756, 63.8321 which is equivalent to: RA(J2000) = +08h 26m 42.14s Dec(J2000) = +63d 49' 55.6" with an uncertainty of 4.8 arcseconds (radius, 90% containment). This location is 26 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 data is not immediately available. Burst Advocate for this burst is L. M. Z. Hagen (lea.zernow.hagen 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/too.html.)