TITLE: GCN CIRCULAR NUMBER: 45812 SUBJECT: GRB 261005B: Swift detection of a burst DATE: 26/10/05 22:04:52 GMT FROM: Jimmy DeLaunay at PSU T. M. Parsotan (GSFC), R. Brivio (INAF-OAB), J. J. DeLaunay (PSU), R. Gupta (NASA GSFC), N. P. M. Kuin (UCL-MSSL), A. Y. Lien (U Tampa), A. Mei (INAF-OAB), K. L. Page (U Leicester), D. M. Palmer (LANL) and C. Salvaggio (INAF-OAB) report on behalf of the Neil Gehrels Swift Observatory Team: At 21:39:06 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 261005B (trigger=1515414). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec = 255.327, +1.590 deg which is RA(J2000) = 17h 01m 19s Dec(J2000) = 01d 35' 25" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a multi-peaked structure with a duration of about 40 sec. The peak count rate was ~2000 counts/sec (15-350 keV), at ~4 sec after the trigger. The XRT began observing the field at 21:41:10.7 UT, 124.1 seconds after the BAT trigger. No source was detected in the 2.5-s promptly available image. We are waiting for the full dataset to detect and localise the XRT counterpart. There are no UVOT data available at this time. Burst Advocate for this burst is T. M. Parsotan (tyler.parsotan 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/)