[vsnet-grb-info 2870] GRB060204a: Swift XRT Source is not GRB Afterglow

[GCN Circulars]

TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  4707
SUBJECT: GRB060204a: Swift XRT Source is not GRB Afterglow
DATE:    06/02/07 18:22:26 GMT
FROM:    David Morris at PSU/Swift-XRT  <morris at astro.psu.edu>

D. Morris (PSU), D. Burrows (PSU), N. Gehrels (GSFC) on behalf of the 
Swift XRT team:

Further Swift XRT observations of the X-ray source detected within the 
INTEGRAL error circle (GCN 4685, Morris et al) have shown that the 
source is not fading. This information, together with the coincident, 
bright, non-fading source detected in the UVOT (GCN 4698, Cucchiara et 
al) and the archival ROSAT pointed observation detection of an X-ray 
source consistent with this source position (GCN 4700, Halpern), 
indicates that this source is not the afterglow of GRB060204a.

Swift XRT has now collected 24ks of data on this field, producing an 
upper limit on the unabsorbed flux of the afterglow in the 0.2-10keV 
band of 2e-14 ergs/cm2/s at a mean epoch of T+120ks. This upper limit 
assumes an absorbed powerlaw spectrum with photon index of 2 and 
galactic absorption of 1e21cm-2. No further observations are planned.

We note that Swift BAT and XRT have previously detected GRBs which have 
subsequently become undetectable to a similar limiting flux level in the 
XRT on timescales similar to our observation of this field, including 
GRB050421, GRB051117b and GRB051210.

This circular is an official product of the Swift XRT Team.