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GCN Circular 24898

Subject
GRB 190610A: Further Swift-XRT observations
Date
2019-06-28T14:21:27Z (5 years ago)
From
Phil Evans at U of Leicester <pae9@leicester.ac.uk>
P.A. Evans (U. Leicester) reports on behalf of the Swift-XRT team:

Swift-XRT has carried out further observations of GRB 190610A (Palmer et 
al. GCN Circ. 24783, Beardmore et al., GCN Circ. 24883), in order to 
ascertain whether the faint source in the BAT error circle ("Source 7") 
is fading. Marginal evidence of fading has been detected.

In our later-epoch observations, the source is not detected at the 
3-sigma level. The 3-sigma upper limit is 1.27 x 10^-3 ct/sec, or a 
1-sigma confidence interval count-rate is 3.2 (+5.6, -1.7) x 10^-4 
ct/sec (all rates are 0.3-10 keV). The original detection had a count 
rate of 1.76 (+0.83, -0.64) x 10^-3 ct/sec.

Thus the source appears to be fading, but only at the 2.1-sigma level.

Given the low significance of the fading, the faintness of the source, 
and the fact that low-level variability is not uncommon among X-ray 
sources, we cannot say with confidence that this is definitely the 
afterglow of GRB 190610A, however it remains a tantalising possibility.
Due to the faint nature of the object, no further XRT observations are 
planned.

The details of the source can be viewed, and the light curve rebinned, 
at: http://www.swift.ac.uk/ToO_GRBs/00020896/Source7.php

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