TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  3086
SUBJECT: GRB 050306: Confirmation of X-ray afterglow
DATE:    05/03/11 17:51:30 GMT
FROM:    David Burrows at PSU/Swift  <dxb15@psu.edu>

V. Mangano, G. Cusumano, T. Mineo (INAF-IASF/Palermo), M. Perri, P. Giommi, 
M. Capalbi, F. Tamburelli (ASDC), D. N. Burrows, D. C. Morris, J. Hill, M. 
Chester (PSU), A. Moretti, D. Malesani (INAF-OAB), O. Godet, P. T. O'Brien 
(U. Leicester), L. Cominsky (Sonoma State U.), J. Greiner (MPE), D. 
Hinshaw, and N. Gehrels (GSFC),  report on behalf of the Swift XRT team:

The Swift X-Ray Telescope (XRT) observed the field of GRB 050306 (GCN 
3071,  Markwardt et al.) for a second time on 2005-03-10 from  01:08:09 UT 
until 15:46:39 UT.  We confirm that the source identified by Perri et al. 
(GCN 3075) has faded from view and is therefore the likely X-ray afterglow 
of this burst.

Only the Photon Counting mode, which provides the best XRT sensitivity, was 
used for this observation.  The total exposure time was 10205 s. No X-ray 
emission was found from the XRT candidate afterglow detected on March 7 
during the first XRT follow-up observation of the field (GCN 3075, Perri et 
al.).  We place a three sigma upper limit on the 0.5-10 keV count rate of 
1.4e-3 cts/s which is significantly lower than the count rate observed on 
March 7 (3.3e-3 cts/s), implying that the source has faded.

We conclude that the candidate reported in GCN 3075 is the X-ray afterglow 
of GRB 050306.  The updated position for this source is:

RA(J2000) = 18 49 14.1
Dec(J2000) = -09 09 11.2

This position is based on 12322s of data from March 7, 2005 (about 3 times 
the amount used in our preliminary report in GCN 3075).  The position 
uncertainty is estimated to be about 6 arcseconds.