GCN Circular 9046

J. Kennea (PSU), P. Evans and M. Goad (U Leicester) report on behalf of 
the Swift/XRT Team:

Further analysis of the candidate afterglow of GRB 090328 has been 
performed utilizing downlinked Swift XRT and UVOT data. Using 1329 s of 
XRT Photon Counting mode data and 2 UVOT images, we find an 
astrometrically corrected X-ray position (using the XRT-UVOT alignment and 
matching UVOT field sources to the USNO-B1 catalogue): RA, Dec = 90.66494, 
-41.88265 which is equivalent to:

RA (J2000):  06 02 39.58
Dec (J2000): -41 52 57.5

with an uncertainty of 2.0 arcsec (radius, 90% confidence). Position 
enhancement is described by Goad et al. (2007, A&A, 476, 1401 
http://www.swift.ac.uk/xrt_positions/Goad.pdf), the current algorithm is 
an extension of this method.

Swift/UVOT detects a point source at a location consistant with the 
XRT error circle, detected in the U and White filters. A catalogue search 
does not reveal any known source at the location of this source. We 
tentatively suggest that this UVOT source may be the optical afterglow of 
GRB 090328, although this cannot be confirmed until either the optical or 
X-ray afterglow candidates are seen to fade.