GCN Circular 41136

J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), T. Sbarrato
(INAF-OAB), P. D'Avanzo (INAF-OAB), M.G. Bernardini (INAF-OAB), D.N.
Burrows (PSU), M.A. Williams (PSU), S. Dichiara (PSU) and P.A. Evans
(U. Leicester) reports on behalf of the Swift-XRT team:

Swift-XRT has performed follow-up observations of the MAXI-detected
burst GRB 250721A in a series of observations tiled on the sky.  The
total exposure time is	1.4 ks, distributed over 5 tiles; the maximum
exposure at a single sky location in the tiling was 569 s. The data
were collected between T0+16.2 ks and T0+22.9 ks, and are entirely in
Photon Counting (PC) mode. 

No X-ray sources have been detected. The 3-sigma upper limit in the
field (not including the regions where the tiles overlap) ranges from
~0.02 to ~0.05 ct s^-1, corresponding to a 0.3-10 keV observed flux of
6.5e-13 to 2.2e-12 erg cm^-2 s^-1 (assuming a typical GRB spectrum).

The results of the XRT-team automatic analysis of the tiled XRT
observations, including a position-specific upper limit calculator, are
available at https://www.swift.ac.uk/xrt_products/TILED_GRB00137.

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