TITLE:   GCN CIRCULAR
NUMBER:  18101
SUBJECT: GRB 150724B: Swift-XRT afterglow detection
DATE:    15/08/01 05:05:00 GMT
FROM:    Kim Page at U.of Leicester  <kpa@star.le.ac.uk>

J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), C. Pagani (U.
Leicester), V. D'Elia (ASDC), A. D'ai (INAF-IASFPA), A. Maselli 
(INAF-IASFPA), L.M. McCauley (PSU), J.A. Kennea (PSU), B. Sbarufatti
(INAF-OAB/PSU) and P.A. Evans (U. Leicester) report on behalf of the
Swift-XRT team:

Swift-XRT has conducted further observations of the field of the
Fermi/LAT-detected burst GRB 150724B (Bissaldi et al. GCN Circ. 18065).
The observations now extend from T0+88.6 ks to T0+607.8 ks. The source
previously reported by Osborne et al. (GCN Circ. 18069), "Source 1", is
fading with 3-sigma significance, and is therefore likely the GRB
afterglow.  The position of this source is RA, Dec=351.8905, +3.8181
which is equivalent to:

RA (J2000): 23:27:33.71
Dec(J2000): +03:49:05.2

with an uncertainty of 4.1 arcsec (radius, 90% confidence).  This
position is 9.1 arcmin from the Fermi/LAT position.  The source is
fading with alpha >0.3.

The results of the XRT-team automatic analysis of the likely afterglow
are at http://www.swift.ac.uk/ToO_GRBs/00020543/index_1.php.
The results of the full analysis of the XRT observations are available
at http://www.swift.ac.uk/ToO_GRBs/00020543.

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