TITLE: GCN CIRCULAR NUMBER: 15269 SUBJECT: GRB 130929A: Swift detection of a burst DATE: 13/09/29 10:07:59 GMT FROM: Jamie A. Kennea at PSU/Swift-XRT F. E. Marshall (NASA/GSFC), J. R. Cummings (NASA/UMBC), J. A. Kennea (PSU), C. Pagani (U Leicester), K. L. Page (U Leicester), M. H. Siegel (PSU) and T. N. Ukwatta (MSU) report on behalf of the Swift Team: At 09:36:33 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 130929A (trigger=572308). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 135.069, -47.565 which is RA(J2000) = 09h 00m 17s Dec(J2000) = -47d 33' 53" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a single peak structure with a duration of about 10 sec. The peak count rate was ~3407 counts/sec (15-350 keV), at ~0 sec after the trigger. The XRT began observing the field at 09:38:14.6 UT, 101.5 seconds after the BAT trigger. Using promptly downlinked data we find an uncatalogued X-ray source with an enhanced position: RA, Dec 135.0241, -47.5605 which is equivalent to: RA(J2000) = 09h 00m 05.78s Dec(J2000) = -47d 33' 37.9" with an uncertainty of 2.1 arcseconds (radius, 90% containment). This location is 110 arcseconds from the BAT onboard position, within the BAT error circle. This position may be improved as more data are received; the latest position is available at http://www.swift.ac.uk/sper. A power-law fit to a spectrum formed from promptly downlinked event data does not constrain the column density. UVOT took a finding chart exposure of 150 seconds with the White filter starting 280 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 0% 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 F. E. Marshall (marshall AT milkyway.gsfc.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.)