TITLE: GCN CIRCULAR NUMBER: 40411 SUBJECT: GRB 250509A: Enhanced Swift-XRT position DATE: 25/05/10 01:51:55 GMT FROM: Phil Evans at U of Leicester pae9@star.le.ac.uk

A.P. Beardmore, P.A. Evans, M.R. Goad and J.P. Osborne (U. Leicester) report on behalf of the Swift-XRT team.

Using 877 s of XRT Photon Counting mode data and 2 UVOT images for GRB 250509A, 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 = 46.44965, -38.84201 which is equivalent to:

RA (J2000): 03h 05m 47.92s Dec (J2000): -38d 50' 31.2"

with an uncertainty of 2.3 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).

This circular was automatically generated, and is an official product of the Swift-XRT team.

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