TITLE: GCN CIRCULAR NUMBER: 17526 SUBJECT: GRB 150302A: Swift detection of a burst DATE: 15/03/02 05:56:18 GMT FROM: David Palmer at LANL A. Y. Lien (GSFC/UMBC), M. M. Chester (PSU), M. De Pasquale (INAF-IASFPA), A. Maselli (INAF-IASFPA), D. M. Palmer (LANL) and M. H. Siegel (PSU) report on behalf of the Swift Team: At 05:42:36 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 150302A (trigger=633237). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 175.508, +36.827 which is RA(J2000) = 11h 42m 02s Dec(J2000) = +36d 49' 37" 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 30 sec. The peak count rate was ~800 counts/sec (15-350 keV), at ~2 sec after the trigger. The XRT began observing the field at 05:44:17.5 UT, 100.9 seconds after the BAT trigger. XRT found a bright, uncatalogued X-ray source located at RA, Dec 175.5314, 36.8110 which is equivalent to: RA(J2000) = +11h 42m 7.54s Dec(J2000) = +36d 48' 39.6" with an uncertainty of 5.9 arcseconds (radius, 90% containment). This location is 88 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 2 seconds with the White filter starting 109 seconds after the BAT trigger. No credible afterglow candidate has been found in the initial data products. Results from the 2.7'x2.7' sub-image are not available at this time. Results from the list of sources generated on-board are not available at this time. No correction has been made for the expected extinction corresponding to E(B-V) of 0.02. Burst Advocate for this burst is A. Y. Lien (amy.y.lien AT nasa.gov). 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.)