GCN Circular 9869

C. A. Swenson (PSU) and M. H. Siegel (PSU) report on behalf of the Swift
UVOT team:

The Swift/UVOT began observations of the field of GRB090902B
approximately 12.5 hours after the Fermi GBM/LAT trigger (de Palma et
al., GCN #9867, Bissaldi et al., GCN #9866).  Within the initial 4.2"
XRT error circle (Kennea et al., GCN #9868) we find a very faint source:

Filter    T_start(s)    T_stop(s)    Exp(s)      Mag

u         273627410     273634846     2691     20.41 +- 0.20 (5.5-sigma)

This source does not seem to appear in the DSS; however, its proximity
to another DSS source, also within the XRT error circle, makes
identifying this source as the afterglow difficult.  We await an
enhanced XRT position and/or ground-based detection to confirm the
nature of this potential afterglow candidate.

The values quoted above are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.04 in the direction of the burst
(Schlegel et al. 1998).