TITLE: GCN CIRCULAR NUMBER: 6125 SUBJECT: GRB070223: Swift burst DATE: 07/02/23 01:43:51 GMT FROM: Scott Barthelmy at NASA/GSFC L. Vetere (PSU), S. D. Barthelmy (GSFC), D. N. Burrows (PSU), S. Campana (INAF-OAB), M. M. Chester (PSU), N. Gehrels (NASA/GSFC), D. Grupe (PSU), J. A. Kennea (PSU), W. B. Landsman (NASA/GSFC), F. E. Marshall (NASA/GSFC), D. M. Palmer (LANL), M. Stamatikos (NASA/ORAU) and E. Troja (INAF-IASFPA) report on behalf of the Swift Team: At 01:15:00 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 070223 (trigger=261664). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 153.452, +43.121 which is RA(J2000) = 10h 13m 49s Dec(J2000) = +43d 07' 16" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve shows several peaks with a duration of about 50 sec. The peak count rate was ~1000 counts/sec (15-350 keV), at ~0 sec after the trigger. The XRT began observing the field at 01:16:50 UT, 110 seconds after the BAT trigger. XRT found a bright, fading, uncatalogued X-ray source located at RA, Dec 153.4533, +43.1336 which is RA(J2000) = 10h 13m 48.7s Dec(J2000) = 43d 08' 00.9" with an uncertainty of 4.7 arcseconds (radius, 90% containment). This location is 45 arcseconds from the BAT on-board position, within the BAT error circle. The initial flux in the 2.5s image was 3.0e-09 erg/cm2/s (0.2-10 keV). UVOT took a finding chart exposure of nominal 100 seconds with the White (160-650 nm) filter starting 120 seconds after the BAT trigger, and a finding chart in V starting 226 seconds after the trigger. No afterglow candidate has been found in the initial data products. Image catalog data are not available at this time. The 2.7'x2.7' immediately available image covers 100% of the XRT error circle. The list of sources is typically complete to about 18 mag. No correction has been made for the expected extinction corresponding to E(B-V) of 0.01.