NASA Swift: GRB 060427: Swift detection of a burst

TITLE: GCN GRB OBSERVATION REPORT
NUMBER: 5006
SUBJECT: GRB 060427: Swift detection of a burst
DATE: 06/04/27 12:06:37 GMT
FROM: Scott Barthelmy at NASA/GSFC Scott@lheamail.gsfc.nasa.gov

V. Mangano (INAF-IASFPA), S. D. Barthelmy (GSFC), S. Campana (INAF-OAB), J. R. Cummings (NASA/ORAU), J. A. Kennea (PSU), H. A. Krimm (GSFC/USRA), F. E. Marshall (NASA/GSFC), K. L. Page (U Leicester), D. M. Palmer (LANL), P. Romano (INAF-OAB) and D. E. Vanden Berk (PSU) report on behalf of the Swift Team:

At 11:43:10 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 060427 (trigger=207281). Swift slewed immediately to the burst. The BAT on-board calculated location is RA,Dec 124.303, +62.617 {08h 17m 13s, +62d 37′ 02″} (J2000) with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). This was an image trigger so the TDRSS lightcurve does not show any significant activity.

The XRT began observing the field at 11:45:20 UT, 130 seconds after the BAT trigger. XRT found a fading, uncatalogued X-ray source located at RA(J2000) = 08h 17m 04.5s, Dec(J2000) = +62d 40′ 17.4″, with an estimated uncertainty of 5.4 arcseconds (90% confidence radius). This location is 204 arcseconds from the BAT on-board position, outside the BAT error circle. The initial flux in the 2.5s image was 9.6e-10 erg/cm2/s (0.2-10 keV).

UVOT took a finding chart exposure of 400 seconds with the V filter starting 133 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 typical 3-sigma upper limit has been about 18.5 mag. The 8’x8′ region for the list of sources generated on-board covers 100% of the XRT error circle. The list of sources has an upper limit of 19.2 mag. No correction has been made for the expected extinction of about 0.2 magnitudes.