[vsnet-grb-info 4419] GRB 070309: variability of the XRT afterglow candidate

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  6200
SUBJECT: GRB 070309: variability of the XRT afterglow candidate
DATE:    07/03/12 17:02:35 GMT
FROM:    Cristiano Guidorzi at INAF-OAB  <cristiano.guidorzi at brera.inaf.it>

S.D. Vergani (Dunsink observatory-DIAS, DCU), P. Romano (INAF-OAB, Univ. 
Bicocca),
C. Guidorzi (INAF-OAB, Univ. Bicocca), A. Moretti (INAF-OAB) report on 
behalf
of the Swift-XRT team:

We continued to analyse the XRT data regarding the source reported by
Vergani et al. in GCN Circ. 6187.
We collected a total of 21 counts for a total exposure time of about
17ks. It is not possible to extract a proper light curve or spectrum.
We divided the observations in two consecutive blocks, with exposures
of 7672 s and of 9623 s, collecting 16 and 5 counts, respectively.
In the assumption of a constant rate source, the probability of having
equally or less uniformly distributed counts is estimated to be smaller 
than 1%.
We conclude that this seems to be a varying source but at the present
time we cannot confirm that this is the X-ray afterglow of GRB070309.

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