GCN Circular 42417

D.N. Burrows (PSU), S. Lanava (PSU), S. Dichiara (PSU), J.P. Osborne
(U. Leicester), K.L. Page (U. Leicester), M. Capalbi (INAF-OAR), M.
Perri (SSDC & INAF-OAR), 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
Fermi/LAT-detected burst GRB 251022A in a series of observations tiled
on the sky.  The total exposure time is  4.6 ks, distributed over 4
tiles; the maximum exposure at a single sky location in the tiling was
2.5 ks. The data were collected between T0+26.7 ks and T0+71.7 ks, and
are entirely in Photon Counting (PC) mode. 

Seven uncatalogued X-ray sources have been detected, however none of
them is above the RASS limit or shows definitive signs of fading in the
X-rays. 

Source 4 is 2.6 arcsec from the reported optical transient GOTO25iym
(O'Neill et al., GCN Circ. 42386
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 ) and thus is likely the counterpart to
that transient and the GRB afterglow, though we cannot at present
confirm fading in X-rays. The details of this source are:

Source 4:
  RA (J2000.0):  65.4968  =  04h 21m 59.23s
  Dec (J2000.0): -18.9188  =  -18d 55' 07.8"
  Error: 4.8 arcsec (radius, 90% conf.)
  Count-rate: 0.0110 [+0.0026, -0.0025] ct s^-1   
  Distance: 1463 arcsec from Fermi/LAT position.
  Flux: (2.96 [+0.71, -0.67])e-13 erg cm^-2 s^-1 (observed, 0.3-10 keV)

The other 6 uncatalogued sources detected are enumerated below:

Source 1:
  RA (J2000.0):  65.0135  =  04h 20m 03.25s
  Dec (J2000.0): -19.3306  =  -19d 19' 50.1"
  Error: 6.3 arcsec (radius, 90% conf. [Enhanced position])
  Count-rate: 0.0173 [+0.0061, -0.0050] ct s^-1   
  Distance: 1247 arcsec from Fermi/LAT position.
  Flux: (3.5 [+1.2, -1.0])e-12 erg cm^-2 s^-1 (observed, 0.3-10 keV)

Source 2:
  RA (J2000.0):  65.0984  =  04h 20m 23.62s
  Dec (J2000.0): -19.2625  =  -19d 15' 45.2"
  Error: 5.4 arcsec (radius, 90% conf.)
  Count-rate: 0.0115 [+0.0046, -0.0037] ct s^-1   
  Distance: 971 arcsec from Fermi/LAT position.
  Flux: (4.4 [+1.8, -1.4])e-13 erg cm^-2 s^-1 (observed, 0.3-10 keV)

Source 5:
  RA (J2000.0):  65.3796  =  04h 21m 31.10s
  Dec (J2000.0): -18.9857  =  -18d 59' 08.4"
  Error: 6.0 arcsec (radius, 90% conf.)
  Count-rate: (7.7 [+2.6, -2.1])e-3 ct s^-1   
  Distance: 1167 arcsec from Fermi/LAT position.
  Flux: (2.17 [+0.72, -0.60])e-13 erg cm^-2 s^-1 (observed, 0.3-10 keV)

Source 6:
  RA (J2000.0):  65.5456  =  04h 22m 10.93s
  Dec (J2000.0): -19.1086  =  -19d 06' 30.8"
  Error: 6.5 arcsec (radius, 90% conf.)
  Count-rate: (6.0 [+2.5, -2.0])e-3 ct s^-1   
  Distance: 917 arcsec from Fermi/LAT position.
  Flux: (9.1 [+3.9, -3.0])e-14 erg cm^-2 s^-1 (observed, 0.3-10 keV)

Source 8:
  RA (J2000.0):  65.4382  =  04h 21m 45.16s
  Dec (J2000.0): -19.0268  =  -19d 01' 36.6"
  Error: 7.8 arcsec (radius, 90% conf.)
  Count-rate: (3.2 [+1.8, -1.3])e-3 ct s^-1   
  Distance: 1038 arcsec from Fermi/LAT position.
  Flux: (6.8 [+3.9, -2.8])e-14 erg cm^-2 s^-1 (observed, 0.3-10 keV)

Source 9:
  RA (J2000.0):  65.3956  =  04h 21m 34.95s
  Dec (J2000.0): -19.0576  =  -19d 03' 27.4"
  Error: 6.3 arcsec (radius, 90% conf.)
  Count-rate: (3.6 [+2.1, -1.5])e-3 ct s^-1   
  Distance: 910 arcsec from Fermi/LAT position.
  Flux: (1.15 [+0.65, -0.48])e-13 erg cm^-2 s^-1 (observed, 0.3-10 keV)

Two catalogued sources were also detected.

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_GRB00139.

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