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GCN Circular 6200

GRB 070309: variability of the XRT afterglow candidate
2007-03-12T17:02:35Z (17 years ago)
Cristiano Guidorzi at INAF-OAB <>
S.D. Vergani (Dunsink observatory-DIAS, DCU), P. Romano (INAF-OAB, Univ. 
C. Guidorzi (INAF-OAB, Univ. Bicocca), A. Moretti (INAF-OAB) report on 
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.

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