[vsnet-grb-info 3645] GRB 060825: XRT Team Refined Analysis

[GCN Circulars]

TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  5479
SUBJECT: GRB 060825: XRT Team Refined Analysis
DATE:    06/08/25 16:03:09 GMT
FROM:    Kim Page at U.of Leicester  <kpa at star.le.ac.uk>

A.P. Beardmore, K.L. Page (U. Leicester) & G. Sato (GSFC/ISAS) report on 
behalf of the Swift-XRT team:

We have analysed the first 4 orbits of Swift-XRT data obtained for GRB 060825
(trigger 226382). From 3660 seconds of data, we find a refined position of:

RA(J2000)  =   01 12 29.00
Dec(J2000) =  +55 47 46.5

with an uncertainty of 4.1 arcsec (90% containment). This is 0.8 arcsec
from the XRT position reported in GCN Circ. 5471 (Sato et al.), and 18.6
arcsec from the refined BAT position in GCN Circ. 5478 (Fenimore et al.).

The X-ray afterglow is faint, initially only 0.8 count/s, 74s after
the BAT trigger, decaying with a slope of alpha = 0.87 +/- 0.09 out to 20ks.
There is, however, a small flare centred at 220s, where the count rate rises
to 1.2 count/s.

The X-ray spectrum from the first four orbits can be well fitted by an
absorbed power-law, with a photon index of Gamma = 1.64 +/- 0.29 absorbed
by the Galactic column density of 3.0e21 cm^-2. The early time unabsorbed
flux (between 74 - 189s after the trigger) was 3.57e-11 erg cm^-2 s^-1
over the 0.3-10 keV band.

Providing the source decays at the same rate then the count rate is
predicted to be ~0.002 count/s 24 hr after the trigger, which
corresponds to an observed 0.3-10keV flux of 1.20e-13 erg cm^-2 s^-1,
or an unabsorbed flux of 1.58e-13 erg cm^-2 s^-1.

This circular is an offical product of the Swift-XRT team.