TITLE: GCN CIRCULAR NUMBER: 39974 SUBJECT: GRB 250331B: Enhanced Swift-XRT position DATE: 25/03/31 15:22:51 GMT FROM: Phil Evans at U of Leicester pae9@star.le.ac.uk

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

Using 824 s of XRT Photon Counting mode data and 1 UVOT images for GRB 250331B, 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 = 71.37215, +43.81257 which is equivalent to:

RA (J2000): 04h 45m 29.32s Dec (J2000): +43d 48' 45.2"

with an uncertainty of 3.6 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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