TITLE: GCN CIRCULAR NUMBER: 16311 SUBJECT: GRB 140521A: Swift detection of a burst DATE: 14/05/21 17:51:56 GMT FROM: Eleonora Troja at GSFC E. Troja (NASA/GSFC/UMCP), S. B. Cenko (GSFC), J. R. Cummings (NASA/UMBC), V. D'Elia (ASDC), L. M. Z. Hagen (PSU), L. Izzo (URoma/ICRA), J. A. Kennea (PSU), H. A. Krimm (CRESST/GSFC/USRA), V. Mangano (PSU), A. Melandri (INAF-OAB), P. T. O'Brien (U Leicester), K. L. Page (U Leicester), B. Sbarufatti (INAF-OAB/PSU), M. H. Siegel (PSU) and T. N. Ukwatta (MSU) report on behalf of the Swift Team: At 17:34:18 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 140521A (trigger=599546). Swift did not slew to the burst due to an observing constraint. The BAT on-board calculated location is RA, Dec 320.013, +67.602 which is RA(J2000) = 21h 20m 03s Dec(J2000) = +67d 36' 06" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a single-peaked structure with a duration of about 12 sec. The peak count rate was ~3000 counts/sec (15-350 keV), at ~0.1 sec after the trigger. Due to an observing constraint, Swift will not slew until 00:39UT on May 22. There will be no XRT or UVOT data until this time. Burst Advocate for this burst is E. Troja (eleonora.troja 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/too.html.)