TITLE: GCN CIRCULAR NUMBER: 7733 SUBJECT: GRB 080516: Swift detection of a burst DATE: 08/05/16 00:47:29 GMT FROM: David Burrows at PSU/Swift S. T. Holland (CRESST/USRA/GSFC), S. D. Barthelmy (GSFC), D. N. Burrows (PSU), E. A. Hoversten (PSU), J. A. Kennea (PSU), H. A. Krimm (CRESST/GSFC/USRA), F. E. Marshall (NASA/GSFC), K. L. Page (U Leicester), D. M. Palmer (LANL), M. Stamatikos (NASA/ORAU), R. L. C. Starling (U Leicester) and E. Troja (U Leicester/INAF-IASFPA) report on behalf of the Swift Team: At 00:17:07 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 080516 (trigger=311762). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 120.629, -26.176 which is RA(J2000) = 08h 02m 31s Dec(J2000) = -26d 10' 33" 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 20 sec. The peak count rate was ~2500 counts/sec (15-350 keV), at ~0 sec after the trigger. The XRT began observing the field at 00:18:29.9 UT, 82.9 seconds after the BAT trigger. Using promptly downlinked data we find an uncatalogued X-ray source with an enhanced position: RA, Dec 120.64234, -26.15900 which is equivalent to: RA(J2000) = 08h 02m 34.16s Dec(J2000) = -26d 09' 32.4" with an uncertainty of 3.7 arcseconds (radius, 90% containment). This is 75 arcsec from the BAT position, within the BAT error circle. UVOT took a finding chart exposure of nominal 400 seconds with the V filter starting 81 seconds after the BAT trigger. No afterglow candidate has been found in the initial data products. This is a particularly crowded field with many stars. The 8'x8' region for the list of sources generated on-board covers 100% of the XRT error circle. The limiting magnitude is about 17.7. No correction has been made for the large, but uncertain extinction expected. 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.)