TITLE: GCN CIRCULAR NUMBER: 6949 SUBJECT: GRB 071020: Swift detection of a bright burst DATE: 07/10/20 07:18:57 GMT FROM: Scott Barthelmy at NASA/GSFC S. T. Holland (CRESST/USRA/GSFC), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC), A. P. Beardmore (U Leicester), P. A. Evans (U Leicester), N. Gehrels (NASA/GSFC), C. Guidorzi (Univ Bicocca&INAF-OAB), C. Pagani (PSU), K. L. Page (U Leicester), D. M. Palmer (LANL), A. M. Parsons (GSFC), T. Sakamoto (NASA/UMBC), R. L. C. Starling (U Leicester) and T. N. Ukwatta (GSFC/GWU) report on behalf of the Swift Team: At 07:02:26 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 071020 (trigger=294835). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 119.664, +32.861 which is RA(J2000) = 07h 58m 39s Dec(J2000) = +32d 51' 40" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve shows a double peak structure with a duration of about 5 sec. The peak count rate was ~22000 counts/sec (15-350 keV), at ~0 sec after the trigger. The XRT began observing the field at 07:03:28 UT, 61 seconds after the BAT trigger. In 268 s of promptly downlinked data XRT found a bright, fading, uncatalogued X-ray source located at RA, Dec 119.6656, 32.8611 which is RA(J2000) = 07 58 39.74 Dec(J2000) = +32 51 40.0 with an uncertainty of 4.3 arcsec (radius, 90% containment). This location is 5 arcseconds from the BAT on-board position, within the BAT error circle. The initial flux in the 2.5s image was 1.8e-09 erg/cm2/s (0.2-10 keV). There will be no UVOT data products for this burst, because it is still in engineering mode after the recent recovery to the new 3-gyro mode. Burst Advocate for this burst is S. T. Holland (sholland 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.)