TITLE:   GCN CIRCULAR
NUMBER:  25680
SUBJECT: GRB 190823A: Swift-XRT afterglow detection
DATE:    19/09/06 19:19:49 GMT
FROM:    Elena Ambrosi at INAF-IASF  <elena.ambrosi@inaf.it>

V. D'Elia (ASDC), A. D'Ai (INAF-IASFPA), A. Melandri (INAF-OAB), A.
Tohuvavohu (U Toronto), J.A. Kennea (PSU), B. Sbarufatti (PSU), A.P.
Beardmore (U. Leicester), J.P. Osborne (U. Leicester) and P.A. Evans
(U. Leicester) report on behalf of the Swift-XRT team:

Swift-XRT has performed further observations of the MAXI-detected burst
GRB 190823A (Iwakiri et al. GCN Circ. 25456).
The observations now extend from T0+12.3 ks and T0+1148.9 ks with a 
total exposure time of 4.1 ks in Photon Counting (PC) mode.

The source previously reported by Ambrosi et al. (GCN Circ. 25476) is
fading with 3-sigma significance, and is therefore likely the GRB
afterglow.
Using 147 s of PC mode data and 1 UVOT image, we find an enhanced XRT
position (using the XRT-UVOT alignment and matching UVOT field sources
to the USNO-B1 catalogue): RA, Dec = 279.68735, -43.52789 which is
equivalent to:

RA (J2000): 18h 38m 44.97s
Dec(J2000): -43d 31' 40.4"

with an uncertainty of 8.7 arcsec (radius, 90% confidence). This
position is 18.6 arcmin from the MAXI position.  The source is fading
with alpha >0.7.

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00020932.
The results of the full analysis of the tiled XRT observations are
available at https://www.swift.ac.uk/xrt_products/TILED_GRB00085.

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