GCN Circular 41851

J.A. Kennea (PSU), A.P. Beardmore (U. Leicester), J.P. Osborne (U.
Leicester), B. Sbarufatti (INAF-OAB), C. Salvaggio (INAF-OAB), M. Ferro
(INAF-OAB), D.N. Burrows (PSU), S. Lanava (PSU) and P.A. Evans (U.
Leicester) reports on behalf of the Swift-XRT team:

We have analysed 5.5 ks of Photon Counting (PC) mode XRT data for GRB
250917B, collected between T0+142 s and T0+28.4 ks. 

Three uncatalogued X-ray sources have been detected within the
estimated 3-sigma Swift-BAT error region (296 arcsec), however none of
them is above the RASS limit or shows definitive signs of fading.
Therefore, at the present time we cannot identify which, if any, is the
afterglow. Details of these sources are given below:

Source 1:
  RA (J2000.0):  291.3458  =  19h 25m 23.00s
  Dec (J2000.0): +11.1151  =  +11d 06' 54.5"
  Error: 5.5 arcsec (radius, 90% conf. [Enhanced position])
  Count-rate: (5.5 [+1.3, -1.2])e-3 ct s^-1   
  Distance: 113 arcsec from Swift-BAT position.
  Flux: (1.26 [+0.30, -0.28])e-13 erg cm^-2 s^-1 (observed, 0.3-10 keV)

Source 5:
  RA (J2000.0):  291.3929  =  19h 25m 34.30s
  Dec (J2000.0): +11.0748  =  +11d 04' 29.2"
  Error: 7.7 arcsec (radius, 90% conf.)
  Count-rate: (4.6 [+5.4, -3.9])e-4 ct s^-1   
  Distance: 147 arcsec from Swift-BAT position.

Source 6:
  RA (J2000.0):  291.4312  =  19h 25m 43.49s
  Dec (J2000.0): +11.1014  =  +11d 06' 05.0"
  Error: 8.3 arcsec (radius, 90% conf.)
  Count-rate: (7.4 [+6.4, -4.8])e-4 ct s^-1   
  Distance: 192 arcsec from Swift-BAT position.
  Flux: (1.47 [+1.27, -0.95])e-12 erg cm^-2 s^-1 (observed, 0.3-10 keV)

Three 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/01350381.

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