TITLE:   GCN CIRCULAR
NUMBER:  34702
SUBJECT: GRB 230911A: Swift-XRT afterglow detection
DATE:    23/09/15 06:29:37 GMT
FROM:    Phil Evans at U of Leicester <pae9@star.le.ac.uk>

P. D'Avanzo (INAF-OAB), D.N. Burrows (PSU), J. D. Gropp (PSU), S.
Dichiara (PSU), A.P. Beardmore (U. Leicester), J.P. Osborne (U.
Leicester), M.G. Bernardini (INAF-OAB), E. Ambrosi  (INAF-IASFPA)  and
P.A. Evans (U. Leicester) reports on behalf of the Swift-XRT team:

Swift-XRT has performed follow-up observations of the
Fermi/GBM-detected burst GRB 230911A, collecting 2.8 ks of Photon
Counting (PC) mode data between T0+215.5 ks and T0+326.2 ks. 

An uncatalogued X-ray source is detected consistent with the GOTO
position (GCN Circ. 34681) of the fading optical counterpart candidate,
and this is therefore believed to be the afterglow.  The position of
this source (astrometrically enhanced by using the XRT-UVOT alignment
and matching UVOT field sources to the USNO-B1 catalogue) is RA,
Dec=57.5027, -29.8259 which is equivalent to:

RA (J2000): 03:50:0.65
Dec(J2000): -29:49:33.2

with an uncertainty of 3.4 arcsec (radius, 90% confidence). Position
enhancement is described by Goad et al. (2007, A&A, 476, 1401) and
Evans et al. (2009, MNRAS, 397, 177). This position is 3.1 arcsec from
the GOTO position.  

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00021622.
The results of the full analysis of the XRT observations are available
at https://www.swift.ac.uk/ToO_GRBs/00021622.

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