[AAVSO-HEN] GRB 090902B: Enhanced Swift-XRT position

[grb at aavso.org]

The following is a GCN Circular circulated via the AAVSO network.
For an archive and more information on circulars visit:
http://lheawww.gsfc.nasa.gov/docs/gamcosray/legr/bacodine/gcn3_archive.html

TITLE:   GCN CIRCULAR
NUMBER:  9871
SUBJECT: GRB 090902B: Enhanced Swift-XRT position
DATE:    09/09/03 06:25:14 GMT
FROM:    Phil Evans at U of Leicester  <pae9 at star.le.ac.uk>

P.A. Evans (U. Leicester)  reports on behalf of the Swift-XRT team.

Using 2.7 ks of XRT Photon Counting mode data and 2 UVOT images for GRB 
090902B, 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 = 264.93859, 27.32448 which is equivalent to:

RA (J2000): 17h 39m 45.26s
Dec (J2000): +27d 19' 28.1"

with an uncertainty of 2.1 arcsec (radius, 90% confidence).

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.