[AAVSO-HEN] GRB 081221: Enhanced Swift-XRT position

[grb at aavso.org]

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TITLE:   GCN CIRCULAR
NUMBER:  8690
SUBJECT: GRB 081221: Enhanced Swift-XRT position
DATE:    08/12/22 03:22:16 GMT
FROM:    Phil Evans at U of Leicester  <pae9 at star.le.ac.uk>

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

Using 4345 s of XRT Photon Counting mode data and 7 UVOT
images for GRB 081221, 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 = 15.7925, -24.5481 which is equivalent
to:

RA (J2000): 01h 03m 10.20s
Dec (J2000): -24d 32' 53.1"

with an uncertainty of 1.4 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
http://www.swift.ac.uk/xrt_positions/Goad.pdf), the current algorithm is an
extension of this method.

This circular was automatically generated, and is an official product of the
Swift-XRT team.