GCN Circular 5006

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.