[vsnet-grb-info 4900] GRB 070707: Swift-XRT follow-up observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  6626
SUBJECT: GRB 070707: Swift-XRT follow-up observations
DATE:    07/07/15 00:42:06 GMT
FROM:    Andy Beardmore at U Leicester  <apb at star.le.ac.uk>

A.P. Beardmore (U. Leicester) and A. Parsons (GSFC) report on behalf of
the Swift-XRT team:

The Swift XRT obtained further follow-up observations of 
GRB 070707 (Beckmann et al., GCN 6606; Gotz et al., GCN 6607). In an
11.1 ks exposure photon counting mode image taken from 325.1 ks to 
516.6 ks after the trigger, and using the same 10 pixel radius extraction
region as before, we find a 3 sigma upper limit to the observed count
rate of 0.0011 count/s. When compared with the initial XRT detection
(Beardmore et al., GCN 6610) of 0.0066 +/- 0.0013 count/s (where the
error bar is a 1 sigma estimate) we conclude the source has faded and
that it was the X-ray counterpart to the GRB.

An absorbed powerlaw fit to the photon energy distribution of the
source observed during the first XRT observation (from 31.8 ks to 
54.1 ks after the trigger), using Cash statistics and with the NH fixed
at the (Dickey and Lockman) galactic value of 6e20cm^-2, gave a powerlaw
index of 2.7 +/- 0.6. The observed 0.3-10 keV flux was 
(2.4 +2.0 -1.4)e-13 ergs cm^-2 s^-1.

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