TITLE:   GCN CIRCULAR
NUMBER:  16178
SUBJECT: GRB 140428A: Swift-XRT detection of a source
DATE:    14/04/29 05:13:35 GMT
FROM:    Kim Page at U.of Leicester  <klp5@leicester.ac.uk>

K.L. Page (U. Leicester), D. Malesani (DARK/NBI) and D. Kocevski
(NASA/GSFC/ORAU) report on behalf of the Swift-XRT team:

We have analysed the initial downlinked Swift-XRT data for the possible
GRB 140428A (GCN Circ. 16177) and find a fading X-ray source within the
BAT field of view.

Using 1124 s of XRT Photon Counting mode data and 3 UVOT images, we find
an astrometrically corrected X-ray position (using the XRT-UVOT alignment
and matching UVOT field sources to the USNO-B1 catalogue): RA, Dec =
194.36852, 28.38490 which is equivalent to:

RA (J2000):  12h 57m 28.45s
Dec (J2000): +28d 23′ 05.7′′

with an uncertainty of 1.7 arcsec (radius, 90% confidence).

This position may be improved as more data are received. The latest
position can be viewed at http://www.swift.ac.uk/xrt_positions. Position
enhancement is described by Goad et al. (2007, A&A, 476, 1401) and Evans
et al. (2009, MNRAS, 397, 1177).

The light curve can be modelled with a power-law decay with a decay index
of alpha=0.92 (+0.11,-0.10).

We therefore confirm that Swift trigger number 597519 is, indeed, a real
GRB.

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