TITLE: GCN CIRCULAR NUMBER: 45889 SUBJECT: GRB 261010A: Swift detection of a burst DATE: 26/10/10 19:34:53 GMT FROM: Jimmy DeLaunay at PSU A. Y. Lien (U Tampa), R. Gupta (NASA GSFC), N. P. M. Kuin (UCL-MSSL), M. J. Moss (GSFC), K. L. Page (U Leicester), D. M. Palmer (LANL) and M. H. Siegel (PSU) report on behalf of the Neil Gehrels Swift Observatory Team: At 19:17:07 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 261010A (trigger=1516528). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec = 248.752, 26.609 deg, which is RA(J2000) = 16h 35m 00s Dec(J2000) = 26d 36' 33" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a single-peaked structure with a duration of at least 5 sec. The peak count rate was ~7000 counts/sec (15-350 keV), at ~0 sec after the trigger. There may be additional pulse structures that are caused either by the burst or by entry into the SAA. Additional ground data are required to distinguish the burst emission from background noise. The XRT began observing the field at 19:18:41.4 UT, 94.2 seconds after the BAT trigger. XRT found a bright, uncatalogued X-ray source located at RA, Dec 248.7491, 26.5802 which is equivalent to: RA(J2000) = 16h 34m 59.78s Dec(J2000) = +26d 34' 48.7" with an uncertainty of 5.0 arcseconds (radius, 90% containment). This location is 104 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 data are unavailable at this time Burst Advocate for this burst is A. Y. Lien (yarleen AT gmail.com). 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/)