TITLE: GCN CIRCULAR NUMBER: 21264 SUBJECT: GRB 170626A: Swift detection of a burst DATE: 17/06/26 09:53:22 GMT FROM: David Palmer at LANL F. E. Marshall (NASA/GSFC), A. P. Beardmore (U Leicester), A. A. Breeveld (UCL-MSSL), D. N. Burrows (PSU), S. W. K Emery (UCL-MSSL), P. A. Evans (U Leicester), N. P. M. Kuin (UCL-MSSL), K. L. Page (U Leicester), D. M. Palmer (LANL) and B. Sbarufatti (INAF-OAB/PSU) report on behalf of the Swift Team: At 09:37:23 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 170626A (trigger=758766). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 165.414, +56.469 which is RA(J2000) = 11h 01m 39s Dec(J2000) = +56d 28' 09" 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 15 sec. The peak count rate was ~35000 counts/sec (15-350 keV), at ~0 sec after the trigger. The XRT began observing the field at 09:38:21.6 UT, 58.5 seconds after the BAT trigger. XRT found a bright, uncatalogued X-ray source located at RA, Dec 165.3927, 56.4759 which is equivalent to: RA(J2000) = +11h 01m 34.25s Dec(J2000) = +56d 28' 33.2" with an uncertainty of 5.3 arcseconds (radius, 90% containment). This location is 49 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. The initial flux in the 2.5 s image was 1.52e-09 erg cm^-2 s^-1 (0.2-10 keV). The XRT position is 5.4 arcmin away from a magnitude 2 star (Merak), therefore there are no UVOT data for this burst. 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.)