[vsnet-grb-info 3189] GRB060428A: Swift/UVOT observations.

[GCN Circulars]

TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  5024
SUBJECT: GRB060428A: Swift/UVOT observations.
DATE:    06/04/28 15:30:29 GMT
FROM:    Massimiliano de Pasquale at MSSL-UCL  <mdp at mssl.ucl.ac.uk>

  M. De Pasquale (UCL-MSSL), V. Mangano (IASF Palermo) report on
  behalf of the Swift/UVOT team:

   The Swift/UVOT began taking data on the field of GRB060428A
at 03:23:48 UT on 2006-04-28, 60 s after the BAT trigger
(Mangano et al., GCN 5014), with the settling exposure. In the
refined XRT error circle (Magano et al., GCN 5018), we find
a weak (4 sigma detection) optical source in the V band at
about V=20, not present in  USNO B1.0 catalogue. This source
however appears to be constant throughout the observation,
thus further observations will be needed to determine if it
is the optical afterglow of this burst.

No other afterglow candidate was detected at the refined XRT
position in summed images from any of the filters down to the
following three-sigma upper limits.

   Filter  T_range(s)  Exp(s) 3sig_UL

   V        60-7526    1657   20.2
   B       548-7116    442    20.5
   U       524-13380   436    20.5
   UVW1    500-12666   1358   20.0
   UVM2    476-11758   1425   19.9
   UVW2    563-7322    472    19.5

   These upper limits are uncorrected for the strong estimated
Galactic reddening of E_{B-V} = 1.25 mag (Schlegel et al. 1998).