[vsnet-grb-info 10560] GRB 110428A : X-ray afterglow confirmation

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  11989
SUBJECT: GRB 110428A : X-ray afterglow confirmation
DATE:    11/05/02 19:15:40 GMT
FROM:    Andrea Melandri at Liverpool John Moores U  <axm at astro.livjm.ac.uk>

A. Melandri, P. D'Avanzo, R. Margutti (INAF-OAB), B. Sbarufatti (INAF- 
OAB/IASFPA) report on behalf of the  Swift Team:

Swift continued to monitor the field of GRB 110428A (Vasileiou et  
al., GCN 11982) in two different observations carried out on April  
29th and May 1st, 2011.

In the final 18.49 ks of data (at a mean T-T0 = 2.07 days after the  
burst event) we still detect Source #1 reported by Melandri et al.  
(GCN 11984) with count rate of (1.6e-2 +/- 1.1e-3) cts/s, consistent  
with a constant flux for this source.

Source #2 is no longer detected with a 3 sigma upper limit of 1.4e-3  
cts/s. The probability for this source of having a constant flux is  
8e-6. This is evidence of the fading of Source #2 with respect to the  
XRT observation reported in Melandri et al. (GCN 11984). Therefore we  
consider Source #2 as the X-ray afterglow of GRB 110428A.

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