TITLE:   GCN CIRCULAR
NUMBER:  24062
SUBJECT: GRB 190404C: Swift-XRT afterglow detection
DATE:    19/04/08 14:57:46 GMT
FROM:    Valerio D'Elia at ASDC  <valerio.delia@ssdc.asi.it>

P. D'Avanzo (INAF-OAB), J.A. Kennea (PSU), B. Sbarufatti
(INAF-OAB/PSU), D.N. Burrows (PSU), J.P. Osborne (U. Leicester), K.L.
Page (U. Leicester), A.P. Beardmore (U. Leicester), V. D'Elia (ASDC),
A. D'Ai (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
MAXI-detected burst GRB 190404C  (Yamada et al., GCN Circ. 24049). The
observations now extend from T0+7.4 ks to T0+335.5 ks. 

Of the sources reported by D'Avanzo et al. (GCN Circ. 24054), "Source
3" is fading with 3-sigma significance, and is therefore likely the GRB
afterglow. Using 1249 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 = 220.84256, -22.66386
which is equivalent to:

RA (J2000): 14h 43m 22.21s
Dec(J2000): -22d 39' 49.9"

with an uncertainty of 2.8 arcsec (radius, 90% confidence). This
position is 4.1 arcmin from the MAXI position. 

The light curve can be modelled with a power-law decay with a decay
index of alpha=0.72 (+0.39, -0.22).

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00020887.
The results of the full analysis of the tiled XRT observations are
available at http://www.swift.ac.uk/xrt_products/TILED_GRB00079.

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