TITLE:   GCN CIRCULAR
NUMBER:  9024
SUBJECT: GRB 090323: Possible XRT Counterpart
DATE:    09/03/24 03:31:40 GMT
FROM:    Jamie A. Kennea at PSU/Swift-XRT  <kennea@astro.psu.edu>

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

At 19:27UT on March 23rd, 2009, Swift began a TOO observation of the 
Fermi/LAT error circle of GRB 090323 (GCN #9021). Ground analysis of the 
initial data finds an uncatalogued point source inside the LAT error 
circle. Currently only one orbit of data has been downlinked so it is not 
possible to determine if the source is fading.

Using 1137 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 = 
190.70940, 17.05390 which is equivalent to:

RA (J2000):  12 42 50.26
Dec (J2000): +17 03 14.2

with an uncertainty of 2.7 arcsec (radius, 90% confidence). This position 
is 1.9 arcminutes from the LAT on-ground localization given in GCN #9021.

This position may be improved as more data are received. The latest 
position can be viewed at http://www.swift.ac.uk/xrt_positions. 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.