[vsnet-grb-info 3807] GRB 060927: Swift XRT Team refined analysis

[GCN Circulars]

TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  5641
SUBJECT: GRB 060927: Swift XRT Team refined analysis 
DATE:    06/09/27 23:19:06 GMT
FROM:    Kim Page at U.of Leicester  <kpa at star.le.ac.uk>

E. Troja (INAF-IASFPa), K. L. Page (U. Leicester), D. Burrows (PSU) and L.
M. Barbier (NASA/GSFC) report on behalf of the Swift/XRT team:

We have analysed the first three orbits of Swift data of GRB 060927
(Barbier et al., GCN 5627). The XRT data set consists of 4 ks in Photon
Counting mode (PC).

We derived a refined XRT position of

RA(J2000)   =  21h 58m 12.2s
Dec(J2000)  = +05d  21' 52.2''

with an error of 6" (90% confidence, including boresight uncertainties).
This position is within 1.8" of the initial XRT position, and 4.6" from
the optical afterglow candidate, reported in GCN 5629 (Schaefer et al.).

The lightcurve shows a break at 4 ks after the trigger. The decay before
the break is 0.7 steepening to 1.4 at later times. The spectrum can be
modelled with an absorbed power-law with a spectral index of 1.96+/-0.2
and a column density of 8+/-3 e20 cm^-2. The Galactic absorption in this
direction is 5.2e20 cm^-2.

The average unabsorbed flux for the first three orbits is 5.6e-12 ergs
cm^-2 s^-1. At this decay rate we predict a count rate of 1.2e-3 cts/s at
T+24h, corresponding to an unabsorbed flux of 7.2e-14 ergs cm^-2 s^-1.

This circular is an official product of the Swift XRT Team.