TITLE: GCN CIRCULAR NUMBER: 5988 SUBJECT: GRB 070103: Swift detection of a burst DATE: 07/01/03 21:12:06 GMT FROM: Scott Barthelmy at NASA/GSFC T. Sakamoto (NASA/ORAU), S. D. Barthelmy (GSFC), D. N. Burrows (PSU), M. M. Chester (PSU), J. R. Cummings (NASA/UMBC), N. Gehrels (NASA/GSFC), S. T. Holland (CRESST/GSFC/USRA), S. Immler (GSFC/USRA), J. A. Kennea (PSU), H. A. Krimm (GSFC/USRA), V. Mangano (INAF-IASFPA), F. E. Marshall (NASA/GSFC), K. M. McLean (LANL/UTD), C. Pagani (PSU), S. B. Pandey (UCL-MSSL), A. M. Parsons (GSFC), P. Romano (Univ. Bicocca & INAF-OAB), B. Sbarufatti (INAF-IASFPA), D. E. Vanden Berk (PSU) and H. Ziaeepour (UCL-MSSL) report on behalf of the Swift Team: At 20:46:39.41 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB (trigger=254532). Swift slewed immediately to the burst. The BAT on-board calculated location is RA=352.557, Dec=+26.875 (J2000), which is RA(J2000) = 23h 30m 14s Dec(J2000) = +26d 52' 32" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve shows two peaks separated by ~10 sec and a few more weak peaks extending out to ~T+20 sec. The peak count rate was ~2400 counts/sec (15-350 keV), at ~0 sec after the trigger. The XRT began taking data at 20:47:48 UT, 69 seconds after the BAT trigger. The XRT on-board centroid algorithm did not find a source in the image, however analysis of downlinked data reveals an uncatalogued point source at the position RA=352.5576, Dec=+26.8751 (J2000), which is RA(J2000) = 23h 30m 13.82s Dec(J2000) = +26d 52' 30".21 with 4.74 arcsec error radius (90% containment). UVOT took a finding chart exposure of 100 seconds with the White (160-650 nm) filter starting 74 seconds after the BAT trigger, and a 400 second exposure with the V filter starting 179 seconds after the trigger. No afterglow candidate has been found in the initial data products. The 2.7'x2.7' sub-image covers 100% of the XRT error circle. The 3-sigma upper limit is 19.5 in white, 18.8 in V. No correction has been made for the expected extinction corresponding to E(B-V) of 0.07.