//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6352 SUBJECT: GRB 070427: Swift detection of a burst DATE: 07/04/27 08:48:05 GMT FROM: David Palmer at LANL G. Sato (GSFC/ISAS), S. Campana (INAF-OAB), P. A. Evans (U Leicester), C. Guidorzi (Univ Bicocca&INAF-OAB), C. B. Markwardt (GSFC/UMD), P. T. O'Brien (U Leicester), J. P. Osborne (U Leicester), K. L. Page (U Leicester), D. M. Palmer (LANL), R. L. C. Starling (U Leicester) and H. Ziaeepour (UCL-MSSL) report on behalf of the Swift Team: At 08:31:08 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 070427 (trigger=277356). This burst was too close to the Sun (42 degrees) for Swift to slew to it. The BAT on-board calculated location is RA, Dec 28.862, -27.633 which is RA(J2000) = 01h 55m 27s Dec(J2000) = -27d 37' 57" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a multiple-peaked structure with a duration of about 15 sec. The peak count rate was ~3500 counts/sec (15-350 keV), at ~5 sec after the trigger. The GRB will become observable by the XRT and UVOT on May 5. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6354 SUBJECT: GRB 070427, Swift-BAT Refined Analysis DATE: 07/04/27 18:56:04 GMT FROM: Michael Stamatikos at GSFC G. Sato (GSFC/ISAS), L. Barbier (GSFC), S. D. Barthelmy (GSFC), J. Cummings (GSFC/UMBC), E. Fenimore (LANL), N. Gehrels (GSFC), H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD), D. Palmer (LANL), A. Parsons (GSFC), T. Sakamoto (GSFC/ORAU), M. Stamatikos (GSFC/ORAU), J. Tueller (GSFC) on behalf of the Swift-BAT team: Using the data set from T-240 to T+962 sec from the recent telemetry downlink, we report further analysis of BAT GRB 070427 (trigger #277356) (Sato, et al., GCN Circ. 6352). The BAT ground-calculated position is RA, Dec = 28.871, -27.603 deg which is RA(J2000) = 1h 55m 29.1s Dec(J2000) = -27d 36' 11.2" with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment). The partial coding was 100%. The mask weighted light curve steeply rises at ~ T+0 sec, exhibiting some multi-peak sub structure, falling more gradually until ~T+20 sec, with trivial emission above 100 keV. T90 (15-350 keV) is 11 +- 1 sec (estimated error including systematics). The time-averaged spectrum from T-0.2 to T+13.7 is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 2.08 +- 0.10. The fluence in the 15-150 keV band is 7.2 +- 0.4 x 10^-07 erg/cm^2. The 1-sec peak photon flux measured from T+6.79 sec in the 15-150 keV band is 1.3 +- 0.1 ph/cm^2/sec. All the quoted errors are at the 90% confidence level.