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GCN Circular 28205

GRB 200803A: Swift-XRT afterglow detection
2020-08-03T20:28:04Z (4 years ago)
Andy Beardmore at U Leicester <>
J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), M.G. Bernardini
(INAF-OAB), E. Ambrosi	(INAF-IASFPA) , M. Capalbi (INAF-IASFPA), B.
Sbarufatti (PSU), D.N. Burrows (PSU), J. D. Gropp (PSU) and P.A. Evans
(U. Leicester) report on behalf of the Swift-XRT team:

Swift-XRT has performed follow-up observations of the
Fermi/LAT-detected burst GRB 200803A (Cutini et al. GCN Circ. 28203) in
a series of observations tiled on the sky. The total exposure time is
3.5 ks, distributed over 4 tiles; the maximum exposure at a single sky
location was 1.6 ks. The data were collected between T0+36.3 ks and
T0+46.6 ks, and are entirely in Photon Counting (PC) mode. 

Five uncatalogued X-ray sources are detected, of which one ("Source 1")
is above the RASS limit, and is therefore likely the GRB afterglow.
Using 812 s of PC mode data and 2 UVOT images, we find an enhanced XRT
position (using the XRT-UVOT alignment and matching UVOT field sources
to the USNO-B1 catalogue): RA, Dec = 311.09390, -62.94478 which is
equivalent to:

RA (J2000): 20h 44m 22.54s
Dec(J2000): -62d 56' 41.2"

with an uncertainty of 2.8 arcsec (radius, 90% confidence). This
position is 9.7 arcmin from the Fermi/LAT position and 1.5 arcsec from
the MASTER optical counterpart reported by Lipunov et al. (GCN Circ.

The light curve can be modelled with a power-law decay with a decay
index of alpha=3.30 (+0.06, -2.56).

If the light curve continues to decay with a power-law decay index of
3.30, the count rate at T+24 hours will be 2.1 x 10^-3 count s^-1

The results of the XRT-team automatic analysis of the likely afterglow
are at

The results of the full analysis of the tiled XRT observations are
available at

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