TITLE: GCN CIRCULAR NUMBER: 12498 SUBJECT: GRB 111029A: Swift detection of a burst DATE: 11/10/29 10:02:02 GMT FROM: Kim Page at U.of Leicester E. Troja (NASA/GSFC/ORAU), S. Campana (INAF-OAB), P. A. Evans (U Leicester), C. Guidorzi (U Ferrara), E. A. Hoversten (PSU), V. Mangano (INAF-IASFPA), C. J. Mountford (U Leicester), P. T. O'Brien (U Leicester), K. L. Page (U Leicester) and D. M. Palmer (LANL) report on behalf of the Swift Team: At 09:44:40 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 111029A (trigger=506519). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 44.691, +57.085 which is RA(J2000) = 02h 58m 46s Dec(J2000) = +57d 05' 07" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a complex structure with a duration of at least 20 sec from T+20 to T+40. The peak count rate was ~1500 counts/sec (15-350 keV), at ~23 sec after the trigger. The XRT began observing the field at 09:47:39.0 UT, 178.5 seconds after the BAT trigger. Using promptly downlinked data we find an uncatalogued X-ray source located at RA, Dec 44.78260, 57.11024 which is equivalent to: RA(J2000) = 02h 59m 7.82s Dec(J2000) = +57d 06' 36.9" with an uncertainty of 4.4 arcseconds (radius, 90% containment). This location is 200 arcseconds from the BAT onboard position. This position may be improved as more data are received; the latest position is available at http://www.swift.ac.uk/sper. We cannot determine whether the source is fading at the present time. As this position is significantly outside the BAT error circle, it is probably unrelated to the trigger. A power-law fit to a spectrum formed from promptly downlinked event data gives a column density consistent with the Galactic value of 6.27 x 10^21 cm^-2 (Kalberla et al. 2005). UVOT took a finding chart exposure of 71 seconds with the White filter starting 163 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 none of the XRT error circle. The 8'x8' region for the list of sources generated on-board covers 100% of the XRT error circle. The list of sources is typically complete to about 18 mag. No correction has been made for the large, but uncertain extinction expected. Burst Advocate for this burst is E. Troja (eleonora.troja 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.)