[vsnet-grb-info 8787] GRB 091221: Enhanced Swift-XRT position

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  10287
SUBJECT: GRB 091221: Enhanced Swift-XRT position
DATE:    09/12/22 09:17:25 GMT
FROM:    Phil Evans at U of Leicester  <pae9 at star.le.ac.uk>

P.A. Evans and M.R. Goad (U. Leicester) report
on behalf of the Swift-XRT team:

Using 3.7 ks of XRT Photon Counting mode data and 7 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 =
55.79749, 23.24119 which is equivalent to:

RA (J2000):  03 43 11.40
Dec (J2000): +23 14 28.3

with an uncertainty of 1.7 arcsec (radius, 90% confidence).

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) and Evans
et al. (2009, MNRAS, 397, 1177).

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