TITLE: GCN CIRCULAR NUMBER: 22699 SUBJECT: Swift Trigger 831888: a possible GRB or Galactic transient DATE: 18/05/11 08:51:18 GMT FROM: Boris Sbarufatti at PSU A. Tohuvavohu (PSU), P. A. Evans (U Leicester), J.D. Gropp (PSU), J. A. Kennea (PSU), A. Y. Lien (GSFC/UMBC), K. L. Page (U Leicester) and B. Sbarufatti (PSU) report on behalf of the Neil Gehrels Swift Observatory Team: At 07:15:39 UT, the Swift Burst Alert Telescope (BAT) triggered and located a possible burst or a Galactic transient (trigger=831888). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 214.508, -62.457 which is RA(J2000) = 14h 18m 02s Dec(J2000) = -62d 27' 24" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve does not show anything significant, as it typical for image triggers (duration is 10.4 min in this case). The XRT began observing the field at 07:33:44.3 UT, 1085.3 seconds after the BAT trigger. No source was detected in 764 s of promptly downlinked data. We are waiting for the full dataset to detect and localise the XRT counterpart. We note that the BAT error circle was not covered by the promptly downlinked data. Because of a known bug in the onboard identification software that affects image triggers longer than 7 minutes happening at the time of a spacecraft slew we believe the identification with a known source in the on-board catalog is incorrect. Since the BAT position is close to the galactic plane (l,b = 312.76,-1.25) at the moment we cannot confidently determine if this is a GRB or a galactic source. We are waiting for the full dataset to properly identify the nature of this trigger. Burst Advocate for this burst is A. Tohuvavohu (aaronb AT swift.psu.edu). 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.)