TITLE: GCN CIRCULAR NUMBER: 43359 SUBJECT: Swift Trigger 1434591: possible GRB 260109C DATE: 26/01/09 13:17:07 GMT FROM: P.A. Evans at U. Leicester <pae9@leicester.ac.uk> T. M. Parsotan (GSFC), P. A. Evans (U Leicester), R. Gupta (NASA GSFC), J. A. Kennea (PSU), N. P. M. Kuin (UCL-MSSL), A. Mei (INAF-OAB), K. L. Page (U Leicester), C. Salvaggio (INAF-OAB) and B. Sbarufatti (INAF-OAB) report on behalf of the Neil Gehrels Swift Observatory Team: At 12:47:15 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 260109C (trigger=1434591). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 123.728, -35.258 which is RA(J2000) = 08h 14m 55s Dec(J2000) = -35d 15' 27" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a complex structure with a duration of about 15 sec. The peak count rate was ~4000 counts/sec (15-350 keV), at ~10 sec after the trigger. The XRT began observing the field at 12:48:41.8 UT, 86.8 seconds after the BAT trigger. No source was detected in 1.3 ks of promptly downlinked data. We are waiting for the full dataset to detect and localise the XRT counterpart. UVOT took a finding chart exposure of 250 seconds with the U filter starting 146 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 25% of the BAT error circle. The typical 3-sigma upper limit has been about 19.2 mag. The 8'x8' region for the list of sources generated on-board covers 100% of the BAT error circle. The limiting magnitude for the list of sources is expected to be about 17.7. No correction has been made for extinction. 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/) View this GCN Circular online at https://gcn.nasa.gov/circulars/43359. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...