TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  3383
SUBJECT: GRB 050509b: Swift XRT Position
DATE:    05/05/09 06:29:23 GMT
FROM:    Jamie A. Kennea at PSU/Swift-XRT  <kennea@astro.psu.edu>

J. A. Kennea, D. N. Burrows, J. Nousek (PSU), C. P. Hurkett, E. Rol, J. 
Osborne, A. Wells (U. Leicester), N. Gehrels (NASA/GSFC), G. Chincarini 
(INAF-OAB) and P. Giommi (ASDC) report on behalf of the Swift XRT team:

The Swift BAT instrument detected GRB 050509b at 04:00:19 UT on 9th May 
2005 (GCN Circ 3381). The observatory executed an automated slew to the 
BAT position and the XRT began taking data at 04:01:12 UT. The XRT was in 
Auto state but was not able to centroid on the afterglow due to low source 
intensity. From downlinked data we find a faint uncatalogued X-ray source 
located at:

RA(J2000) = 12:36:13.6,
Dec(J2000) = +28:58:58.6

We estimate an uncertainty of about 6 arcseconds radius (90% containment). 
This position is 61 arcseconds from the BAT position reported in GCN 3381. 
This source lies 44 arcseconds from the center of the Galaxy Cluster NSC 
J123610+285901. Note that this source position is 157 arcseconds from the 
tentative UVOT optical afterglow counterpart reported in GCN 3381, and 
therefore is not associated with that source.  We cannot yet determine 
whether this X-ray source is fading.  Additional observations are in 
progress.