TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3725 SUBJECT: GRB050801: Swift-BAT detection of a burst DATE: 05/08/01 19:25:50 GMT FROM: Scott Barthelmy at NASA/GSFC D.L. Band (GSFC), S. Barthelmy (GSFC), J. Cummings (GSFC/NRC), N. Gehrels (GSFC), C. Gronwall (PSU) S. Hunsberger (PSU), J. Kennea (PSU), D. Palmer (LANL), M. Perri (ASDC) on behalf of the Swift team: At 18:28:02.07 UT, Swift-BAT triggered and located GRB050801 (trigger=148522). The spacecraft slewed immediately. The BAT on-board calculated location is RA,Dec 204.139d,-21.950d {+13h 36m 33s,-21d 57' 00"} (J2000), with an uncertainty of 3 arcmin (radius, 90% containment, stat+sys). The BAT light curve shows a single FRED structure with a total duration of 3 sec. The peak count rate was ~900 counts/sec (15-350 keV), which peaks at ~T+0.5 seconds. The XRT began observing at 18:29:03 UT, 61 seconds after the BAT trigger. XRT did centroid on a position, but on-ground examination of the image revealed that the object found by the centroiding algorithm is a CCD artifact (Kennea, GCN 3724). Swift-UVOT began observations of GRB 050801 after the slew, however, the UVOT dark burst image did not come down via TDRSS so no information is available at this time. Detailed analysis will be performed when data is available after the next Malindi pass. Because of orbit trajectory with respect to the Malindi ground station, we will not have access to the full data sets to produce the refined analyses for several hours.