TITLE: GCN CIRCULAR NUMBER: 6273 SUBJECT: GRB 070412: Swift detection of a burst DATE: 07/04/12 01:58:32 GMT FROM: David Palmer at LANL P. Romano (Univ. Bicocca & INAF-OAB), S. D. Barthelmy (GSFC), D. N. Burrows (PSU), J. R. Cummings (NASA/UMBC), N. Gehrels (NASA/GSFC), S. T. Holland (CRESST/GSFC/USRA), H. A. Krimm (GSFC/USRA), A. Moretti (INAF-OAB), C. Pagani (PSU), D. M. Palmer (LANL), T. Sakamoto (NASA/ORAU), M. Stamatikos (NASA/ORAU) and D. E. Vanden Berk (PSU) report on behalf of the Swift Team: At 01:27:03 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 070412 (trigger=275119). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 181.505, +40.101 which is RA(J2000) = 12h 06m 01s Dec(J2000) = +40d 06' 03" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a double-peaked structure with peaks at approximately 5 and 30 seconds and a total duration of about 40 sec. The peak count rate was ~2400 counts/sec (15-350 keV), at ~5 sec after the trigger. The XRT began observing the field at 01:28:04 UT, 61 seconds after the BAT trigger. Analysis of XRT downlinked data found an X-ray source located at RA, Dec 181.54, +40.141 which is RA(J2000) = 12h 06m 10.5s Dec(J2000) = 40d 08' 27.8" with an uncertainty of 5.6 arcseconds (radius, 90% containment). This location is 181 arcseconds from the BAT on-board position, outside the BAT error circle. The initial flux in the 2.5s image was 7.0e-10 erg/cm2/s (0.2-10 keV). UVOT took a finding chart exposure of 54 seconds with the White (160-650 nm) filter starting 70 seconds after the BAT trigger. No afterglow candidate has been found in the initial data products. Image catalog data are not available at this time. The 8'x8' region for the list of sources generated on-board 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 extinction of E(B-V)=0.02. The TDRSS transmissions were delayed by 11 minutes due to the trigger occuring during a Malindi downlink.