[vsnet-grb-info 7487] GRB 090328: Updated position/optical afterglow candidate
GCN Circulars
gcncirc at capella.gsfc.nasa.gov
Sun Mar 29 14:46:19 JST 2009
TITLE: GCN CIRCULAR
NUMBER: 9046
SUBJECT: GRB 090328: Updated position/optical afterglow candidate
DATE: 09/03/29 05:46:10 GMT
FROM: Jamie A. Kennea at PSU/Swift-XRT <kennea at astro.psu.edu>
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.
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