TITLE: GCN CIRCULAR NUMBER: 41194 SUBJECT: GRB 250728A: Swift-XRT observations DATE: 25/07/29 09:59:23 GMT FROM: Phil Evans at U of Leicester pae9@star.le.ac.uk
M.A. Williams (PSU), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), A.P. Beardmore (U. Leicester), A. Melandri (INAF-OAR), T. Sbarrato (INAF-OAB), P. D'Avanzo (INAF-OAB), S. Dichiara (PSU), J.A. Kennea (PSU) 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 250728A, collecting 3.1 ks of Photon Counting (PC) mode data between T0+14.6 ks and T0+28.2 ks.
One uncatalogued X-ray source has been detected within the estimated 3-sigma Fermi/GBM error region (394 arcsec), it is below the RASS limit and shows no definitive signs of fading. Therefore, at the present time we cannot confirm this as the afterglow. Details of this source are given below:
Source 3: RA (J2000.0): 260.9895 = 17:23:57.48 Dec (J2000.0): +16.2004 = +16:12:01.6 Error: 6.7 arcsec (radius, 90% conf.) Count-rate: (1.98 [+1.26, -0.93])e-3 ct s^-1 Distance: 154 arcsec from Fermi/GBM position. Flux: (1.34 [+0.85, -0.63])e-13 erg cm^-2 s^-1 (observed, 0.3-10 keV)
Two uncatalogued sources were also detected too far from the GRB position to be likely afterglow candidates.
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/00021852.
This circular is an official product of the Swift-XRT team.
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