TITLE:   GCN CIRCULAR
NUMBER:  18243
SUBJECT: GRB 150902A: Swift-XRT afterglow detection
DATE:    15/09/05 14:09:50 GMT
FROM:    Boris Sbarufatti at INAF-OAB/IASFPA  <boris.sbarufatti@brera.inaf.it>

L.M. McCauley (PSU), J.A. Kennea (PSU), B. Sbarufatti (INAF-OAB/PSU),
A.P. Beardmore (U. Leicester), J.P. Osborne (U. Leicester), V. D'Elia
(ASDC), A. D'ai (INAF-IASFPA), A. Maselli  (INAF-IASFPA) 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 150902A (Arimoto et al. GCN Circ. 18228).
The observations now extend from T0+59.5 ks to T0+192.1 ks. 

Of the sources reported by McCauley et al. (GCN Circ. 18237), "Source
1" is  believed to be the afterglow.  The position of this source is
RA, Dec=214.9796, -69.3536 which is equivalent to:

RA (J2000): 14:19:55.09
Dec(J2000): -69:21:13.1

with an uncertainty of 4.3 arcsec (radius, 90% confidence).  This
position is 73 arcsec from the Fermi/LAT position. 

The light curve can be modelled with a power-law decay with a decay
index of alpha=1.0 (+0.7, -0.4).

The results of the XRT-team automatic analysis of the likely afterglow
are at http://www.swift.ac.uk/ToO_GRBs/00020549/index_1.php.
The results of the full analysis of the XRT observations are available
at http://www.swift.ac.uk/ToO_GRBs/00020549.

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