TITLE: GCN CIRCULAR NUMBER: 9062 SUBJECT: GRB 090401: Swift detection of a burst DATE: 09/04/01 00:23:21 GMT FROM: Scott Barthelmy at NASA/GSFC P. Schady (MSSL-UCL), S. D. Barthelmy (GSFC), N. Gehrels (NASA/GSFC), S. T. Holland (CRESST/USRA/GSFC), H. A. Krimm (CRESST/GSFC/USRA), C. B. Markwardt (CRESST/GSFC/UMD), F. E. Marshall (NASA/GSFC), K. L. Page (U Leicester), D. M. Palmer (LANL), A. M. Parsons (GSFC), B. A. Rowlinson (U Leicester) and L. Vetere (PSU) report on behalf of the Swift Team: At 00:00:59 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 090401 (trigger=348128). The BAT on-board calculated location is RA, Dec 350.909, +29.767 which is RA(J2000) = 23h 23m 38s Dec(J2000) = +29d 46' 00" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve shows a small peak at ~T+30 sec and then two large peaks at ~T+100 and ~T+120 sec. The peak count rate was ~4000 counts/sec (15-350 keV), at ~120 sec after the trigger. Due to an observing constraint, Swift cannot slew to the BAT position. It will not be possible to observe until 2nd May due to a sun constraint. There will thus be no XRT or UVOT data for this trigger. Burst Advocate for this burst is P. Schady (ps AT mssl.ucl.ac.uk). Please contact the BA by email if you require additional information regarding Swift followup of this burst. In extremely urgent cases, after trying the Burst Advocate, you can contact the Swift PI by phone (see Swift TOO web site for information: http://www.swift.psu.edu/too.html.)