[vsnet-grb-info 2368] GRB051028: Swift-XRT refined analysis

[GCN Circulars]

TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  4205
SUBJECT: GRB051028: Swift-XRT refined analysis
DATE:    05/11/07 12:03:55 GMT
FROM:    Kim Page at U.of Leicester  <kpa at star.le.ac.uk>

K.L. Page, M.R. Goad (U. Leicester), D.N. Burrows, J. Racusin (PSU), S.
Oates (MSSL), M. Ajello (MPE) and M. Trippico (GSFC-SSAI) report on behalf
of the Swift XRT team:

We have analysed 38 ks of XRT observations of the HETE burst GRB051028
(trigger number H3951; GCN 4172, Hurley et al.), between approximately 7.1
and 178 hours after the trigger. As reported in GCN 4174 (Racusin et al.),
there is an uncatalogued, fading X-ray source within the HETE error
circle. The refined coordinates for this X-ray afterglow are:

RA(J2000):   01 48 15.1
Dec(J2000): +47 45 12.9

with an estimated uncertainty of 3.8 arcsec (90% containment) and
including the latest XRT boresight correction. The position is 0.6 arcsec
from that given by Racusin et al. (GCN 4174) and 3.9 arcsec from the
optical afterglow detected by the WHT (GCNs 4175, Jelinek et al., and
4176, Pandey et al.)

The X-ray light-curve shows a simple power-law decay with a slope of 1.25
+0.25/-0.16.  The spectrum of the full 38 ks of data can also be modelled
with a power-law, with photon index, Gamma = 1.74 +/- 0.21. There is no
evidence for an absorbing column higher than the Galactic value of 1.2e21
cm^-2.

At 7.1 hours, the 0.3-10 keV observed (unabsorbed) flux was ~1.8e-12
(2.2e-12) erg cm^-2 s^-1. At 178 hours, the afterglow had faded to an
observed (unabsorbed) flux level of 2.3e-14 (2.8e-14) erg cm^-2 s^-1.