TITLE:   GCN CIRCULAR
NUMBER:  6151
SUBJECT: GRB070224: Swift-XRT Astrometrically Corrected Position
DATE:    07/02/26 19:22:30 GMT
FROM:    Judith Racusin at PSU  <racusin@astro.psu.edu>

J. Racusin (PSU), M. Goad (U. Leicester), D.N. Burrows (PSU), O. Godet (U. 
Leicester), R. Starling (U. Leicester) report on behalf of the Swift XRT 
team:

Based on an accurate mapping between the XRT and UVOT detector coordinate 
systems, we have used the simultaneous UVOT V-band images to 
astrometrically correct (relative to stellar catalogues, e.g. USNO-B1) the 
XRT world coordinate system, and thereby refine the XRT position.  We 
obtain a new XRT position at RA,Dec=179.02792,-13.3304 which is:

RA(J2000):  11h 56m 06.7s
Dec(J2000): -13d 19' 49.6"

with an uncertainty of 2.6 arcseconds (90% containment).  This is 3.8 
arcseconds from the refined XRT position (Racusin et al., GCN 6143), and 
2.0 arcseconds from the optical candidate first identified by Thoene et 
al. (GCN 6142).

This circular is an official product of the Swift-XRT team.