TITLE: GCN CIRCULAR NUMBER: 6411 SUBJECT: GRB 070517: Swift detection of a burst DATE: 07/05/17 11:40:57 GMT FROM: Scott Barthelmy at NASA/GSFC S. D. Vergani (DIAS-DCU), S. D. Barthelmy (GSFC), A. P. Beardmore (U Leicester), D. N. Burrows (PSU), S. Campana (INAF-OAB), M. M. Chester (PSU), G. Cusumano (INAF-IASFPA), P. A. Evans (U Leicester), N. Gehrels (NASA/GSFC), J. A. Kennea (PSU), H. A. Krimm (GSFC/USRA), W. B. Landsman (NASA/GSFC), V. Mangano (INAF-IASFPA), A. Moretti (INAF-OAB), P. T. O'Brien (U Leicester), J. P. Osborne (U Leicester), K. L. Page (U Leicester), D. M. Palmer (LANL), P. Romano (Univ. Bicocca & INAF-OAB), G. Sato (GSFC/ISAS), B. Sbarufatti (INAF-IASFPA), M. Stamatikos (NASA/ORAU), R. L. C. Starling (U Leicester), G. Tagliaferri (INAF-OAB), E. Troja (INAF-IASFPA) and H. Ziaeepour (UCL-MSSL) report on behalf of the Swift Team: At 11:20:58 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 070517 (trigger=279494). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 277.579, -62.333 which is RA(J2000) = 18h 30m 19s Dec(J2000) = -62d 19' 56" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve shows two peaks with a duration of about 10 sec. The peak count rate was ~1000 counts/sec (15-350 keV), at ~1 sec after the trigger. The XRT began taking data at 11:22:43 UT, 105 seconds after the BAT trigger. The XRT on-board centroid algorithm did not find a source in the image, but analysis of down-linked data yields a position: RA(J2000) = 18h 30m 29.4s Dec(J2000) = -62d 17' 50.8" with an uncertainty of 5.2 arcsec (radius, 90% containment). This position is 2.4 arcmin from the BAT position. The UVOT is unable to observe the field of GRB070517 due to the presence of a 4th magnitude star 8 arcmin from the burst's location. The Galactic reddening in the direction of the burst is E(B-V) = 0.15.