GCN Circular 9886
Subject
GRB090904A: Correction to enhanced XRT position
Date
2009-09-04T12:32:00Z (15 years ago)
From
Phil Evans at U of Leicester <pae9@star.le.ac.uk>
P.A. Evans (U. Leicester) reports on behalf of the Swift-XRT team:
The automatic enhanced XRT position (GCN 9885) was incorrect and should
be disregarded. The position was obtained by averaging all the PC data
from the first orbit, however the degree of pile up in this period
changes by much more than is normal (see the light curve at:
http://www.swift.ac.uk/xrt_curves/00361830/). As a result, the PSF of
the image did not match any of our calibrated PSFs. We apologise for any
confusion.
The best XRT position available is the enhanced SPER position, which was
distributed as an XRT Position Update GCN notice about at 01:27 UT. This
position is RA, Dec = 100.8858, 50.2038, which corresponds to
RA(J2000.0) = 06h 43m 32.59s
Dec (J2000.0) = +50d 12' 13.6"
with an uncertainty of 2.3 arcsec (radius, 90% confidence).
This circular is an official product of the Swift-XRT team.