TITLE: GCN CIRCULAR NUMBER: 8502 SUBJECT: Swift-BAT Trigger 334129: possible burst DATE: 08/11/09 14:11:03 GMT FROM: David Palmer at LANL S. Immler (CRESST/GSFC/UMD), A. P. Beardmore (U Leicester), D. N. Burrows (PSU), J. R. Cummings (NASA/UMBC), P. A. Evans (U Leicester), N. Gehrels (NASA/GSFC), C. Guidorzi (INAF-OAB), S. T. Holland (CRESST/USRA/GSFC), S. D. Hunsberger (PSU), N. P. M. Kuin (MSSL), J. Mao (INAF-OAB), F. E. Marshall (NASA/GSFC), P. T. O'Brien (U Leicester), K. L. Page (U Leicester), D. M. Palmer (LANL), P. Romano (INAF-IASFPA), R. L. C. Starling (U Leicester), G. Tagliaferri (INAF-OAB) and L. Vetere (PSU) report on behalf of the Swift Team: At 13:47:16 UT, the Swift Burst Alert Telescope (BAT) triggered and located a possible source (trigger=334129). Swift slewed immediately to the location. The BAT on-board calculated location is RA, Dec 350.157, -55.904 which is RA(J2000) = 23h 20m 38s Dec(J2000) = -55d 54' 12" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). This was a 128-second image trigger. As is usual for image triggers, the BAT light curve showed no significant peaks. The XRT began observing the field at 13:50:19.9 UT, 183.1 seconds after the BAT trigger. No source was detected in the promptly available XRT data. 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 187 seconds after the BAT trigger. We do not detect an optical afterglow in any of the UVOT data. The 2.7'x2.7' sub-image covers 25% of the BAT error circle with a 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 0.01. Due to the marginal significance of the BAT image and the non-detection of any source by XRT and UVOT, we cannot confirm that this is a real source. Further analysis will require the Malindi data, which will be downlinked at T+8 hours. Burst Advocate for this trigger is S. Immler (immler@milkyway.gsfc.nasa.gov). Please contact the BA by email if you require additional information regarding Swift followup of this trigger. 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.)