NASA Swift: GRB 060428: Swift detection of a burst
TITLE: GCN GRB OBSERVATION REPORT
NUMBER: 5014
SUBJECT: GRB 060428: Swift detection of a burst
DATE: 06/04/28 03:45:11 GMT
FROM: Scott Barthelmy at NASA/GSFC Scott@lheamail.gsfc.nasa.gov
V. Mangano (INAF-IASFPA), S. D. Barthelmy (GSFC), D. N. Burrows (PSU), J. R. Cummings (NASA/ORAU), N. Gehrels (NASA/GSFC), S. T. Holland (GSFC/USRA), J. A. Kennea (PSU), C. B. Markwardt (GSFC/UMD), F. E. Marshall (NASA/GSFC), D. M. Palmer (LANL) and D. E. Vanden Berk (PSU) report on behalf of the Swift Team:
At 03:22:48 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 060428 (trigger=207364). Swift slewed immediately to the burst. The BAT on-board calculated location is RA,Dec 123.568, -37.165 {08h 14m 16s, -37d 09′ 52″} (J2000) with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve shows a main peak starting at ~T-5 sec and ending at ~T+15 sec. There is a possible second peak going from T+20 to T+40 sec. The peak count rate was ~2500 counts/sec (15-350 keV), at ~4 sec after the trigger.
The XRT began observing the field at 03:23:56 UT, 69 seconds after the BAT trigger. XRT found a fading, uncatalogued X-ray source located at RA(J2000) = 08h 14m 10.9s, Dec(J2000) = -37d 10′ 09.1″, with an estimated uncertainty of 4.7 arcseconds (90% confidence radius). This location is 65 arcseconds from the BAT on-board position, within the BAT error circle. The initial flux in the 2.5s image was 3.2e-09 erg/cm2/s (0.2-10 keV).
UVOT took a finding chart exposure of 400 seconds with the V filter starting 71 seconds after the BAT trigger. No afterglow candidate has been found in the initial data products. The 2.7’x2.7′ sub-image covers 100% of the XRT error circle. The 3-sigma upper limit is about 19.1 mag. The 8’x8′ region for the list of sources generated on-board covers 100% of the XRT error circle. The limiting magnitude is expected to be about 17.5. No correction has been made for the large, but uncertain extinction expected.
