TITLE:   GCN CIRCULAR
NUMBER:  39856
SUBJECT: GRB 250321B: Swift-XRT observations
DATE:    25/03/23 16:57:22 GMT
FROM:    Phil Evans at U of Leicester <pae9@star.le.ac.uk>

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

Swift-XRT has performed follow-up observations of the
SVOM/ECLAIRs-detected burst GRB 250321B, collecting  2.7 ks of Photon
Counting (PC) mode data between T0+81.0 ks and T0+92.8 ks. 

No X-ray sources have been detected. The 3-sigma upper limit in the
field ranges from ~0.005 to ~0.006 ct s^-1, corresponding to a 0.3-10
keV observed flux of 2.1e-13 to 2.4e-13 erg cm^-2 s^-1 (assuming a
typical GRB spectrum).

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/00021824.

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