GCN Circular 3086
Subject
GRB 050306: Confirmation of X-ray afterglow
Date
2005-03-11T17:51:30Z (19 years ago)
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.