TITLE: GCN CIRCULAR NUMBER: 40481 SUBJECT: GRB 250515A: Swift-XRT observations DATE: 25/05/17 08:43:22 GMT FROM: Phil Evans at U of Leicester pae9@star.le.ac.uk

M. Capalbi (INAF-IASFPA), M. Perri (SSDC & INAF-OAR), V. D'Elia (SSDC & INAF-OAR), D.N. Burrows (PSU), M.A. Williams (PSU), S. Dichiara (PSU), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester) and P.A. Evans (U. Leicester) reports on behalf of the Swift-XRT team:

Swift-XRT has performed follow-up observations of the Fermi/GBM-detected burst GRB 250515A, centred on the location of GOTO25cqo (GCN 40464) collecting 4.5 ks of Photon Counting (PC) mode data between T0+88.8 ks and T0+117.8 ks.

No X-ray sources have been detected within the estimated 3-sigma GOTO error region (4.9 arcsec). The 3-sigma upper limit in the field ranges from ~0.002 to ~0.003 ct s^-1, corresponding to a 0.3-10 keV observed flux of 9.2e-14 to 1.4e-13 erg cm^-2 s^-1 (assuming a typical GRB spectrum).

GOTO25cqo has since been classified as a type Ia supernova.

The results of the XRT-team automatic analysis of the XRT observations, including a position-specific upper limit calculator, are available at https://www.swift.ac.uk/ToO_GRBs/00021829.

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

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