GCN Circular 2974

C. Pagani (OAB), J. Kennea, D. N. Burrows, J. E. Hill, J. A. Nousek (PSU), G.
Chincarini, G. Tagliaferri, A. Moretti, P. Romano, S. Campana (OAB), M. Goad,
K. Page, A. Wells, J. Osborne, A. Beardmore (U. Leicester), M. Chester (PSU),
S. Barthelmy, N. Gehrels, N. White (GSFC), P. Schady (MSSL), M. Tripicco
(GSFC), L. Cominsky (Sonoma State U.),
P. Giommi (ASDC) on behalf of the Swift XRT team.

The Swift X-Ray Telescope (XRT) was pointed at GRB050124 ( GCN 2972
Not found
 
 
, Markwardt
et al.; GCN 2973
Not found
 
 
, Cummings et al.) on 2005/01/24 at 14:34 UT.  The spacecraft
did not autonomously slew to the burst since automated slewing was not enabled
at the time the burst occurred.  The observation was performed as a Target of
Opportunity beginning about 3 hours after the burst.  The first XRT exposure
was at 14:35:16 UT.  The observation continued until 15:17:12 UT.  The XRT was
in Auto State and the ToO was performed as if it were an automated burst
observation.  XRT attempted to determine a prompt centroid but found
insufficient counts.  It took one frame in Piled-up Photodiode mode, one in
Low-rate Photodiode mode, and then settled into Windowed Timing mode (1-D
position resolution, 2 ms timing) for the bulk of the observation (1100
frames), with about 220 frames in Photon-Counting mode (2-D position
resolution, 2.5s timing).

We processed the data on the ground and detect a bright X-ray source in this
field.  The X-ray centroid has an approximate location of:
RA(J2000) = 12:51:31.1
Dec(J2000) = 13:02:34.3.

This position is not corrected for stellar aberration, and we estimate an
uncertainty of about 30 arcseconds as a result.  A more accurate position will
be available once the data are processed by the XRT pipeline software.

Checks against SIMBAD and the HEASARC master X-ray catalog yielded no known
source at this position on the sky.   The XRT position is about 70 arcseconds
from the refined BAT positions (GCN 2973
Not found
 
 
).

We have a total of about 600 counts from this object in the first observation
set.  The spectrum appears consistent with a power-law, but detailed fitting
awaits the pipeline-processed data.  Additional automated observations are in
progress when the afterglow field is observable by Swift.

[GCN OPS NOTE (24Jan05): In the first line, the "GRB010124" was changed to "GRB050124"
as per author's request.]