TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  2520
SUBJECT: GRB040106: refined X-ray transient position
DATE:    04/01/21 17:24:04 GMT
FROM:    Darach Watson at U.of Copenhagen  <darach@astro.ku.dk>

J. A. Tedds (University of Leicester) and D. Watson (University of
Copenhagen) report on behalf of a larger collaboration:


The XMM-Newton EPIC coordinates were refined by matching the X-ray sources
in the field to the USNO-A2 catalogue.  The cross-correlation is extremely
good and yields a final source position (J2000) for the X-ray afterglow of

RA: 11 52 12.43, Dec: -46 47 15.9

The 1 sigma error radius is 0.7" (including the residual 0.5" systematic
error from the correlation that is observed in the 1XMM catalogue).

This is not precisely consistent with the position of the fading optical
source reported by Masetti et al. (GCN 2515).  However we note that the
position of the star listed as #4 in the image provided by Masetti et al.,
which corresponds to the USNO-B1 source 0432-0297902 and the relative
position of another star in the field (USNO-B1 0432-0297908), both imply a
shift of ~1" in their coordinates in R.A.  Correcting for this shift we find
the optical transient position consistent with the XMM-Newton position given
above.  This position is not coincident with that of the radio source
reported by Wieringa & Frail (GCN 2516).