[vsnet-grb-info 20547] GRB 180409A: Swift-XRT afterglow detection

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  22643
SUBJECT: GRB 180409A: Swift-XRT afterglow detection
DATE:    18/04/15 03:23:31 GMT
FROM:    Aaron Tohuvavohu at PSU/Swift  <aaronb at swift.psu.edu>

A. Tohuvavohu (PSU), S. J. LaPorte (PSU), A.P. Beardmore (U.
Leicester), S.L. Gibson (U. Leicester), P. D'Avanzo (INAF-OAB), V.
D'Elia (ASDC), A. D'Ai (INAF-IASFPA), J.A. Kennea (PSU), B. Sbarufatti
(INAF-OAB/PSU) 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
IPN-detected burst GRB 180409A (Yoshida et al. GCN Circ. 22635). The
observations now extend from T0+53.4 ks to T0+455.1 ks. The source
previously reported by Tohuvavohu et al. (GCN Circ. 22625), "Source 1",
is fading with 3-sigma significance, and is therefore likely the GRB
afterglow. Using 1887 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 = 175.84306, +36.23354
which is equivalent to:

RA (J2000): 11h 43m 22.33s
Dec(J2000): +36d 14' 00.8"

with an uncertainty of 3.1 arcsec (radius, 90% confidence). This
position is 4.5 arcmin from the IPN position. 

The light curve can be modelled with a power-law decay with a decay
index of alpha=1.0 (+/-0.3).

The results of the XRT-team automatic analysis of the likely afterglow
are at http://www.swift.ac.uk/xrt_products/TILED_GRB00069/Source1.php.
The results of the full analysis of the tiled XRT observations are
available at http://www.swift.ac.uk/xrt_products/TILED_GRB00069.

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