GCN Circular 31051

V. D'Elia (SSDC & INAF-OAR), A. D'Ai (INAF-IASFPA), B. Sbarufatti
(PSU), D.N. Burrows (PSU), J. D. Gropp (PSU), A.P. Beardmore (U.
Leicester), J.P. Osborne (U. Leicester), A. Melandri (INAF-OAB) and
P.A. Evans (U. Leicester) report on behalf of the Swift-XRT team:

Swift-XRT has performed follow-up observations of the
Swift/BAT-GUANO-detected burst GRB 211106A, collecting 5.0 ks of Photon
Counting (PC) mode data between T0+39.2 ks and T0+58.2 ks. 

Eight uncatalogued X-ray sources have been detected, 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 2:
  RA (J2000.0):  343.5852  =  22:54:20.45
  Dec (J2000.0): -53.2303  =  -53:13:49.0
  Error: 3.4 arcsec (radius, 90% conf. [Enhanced position])
  Count-rate: (8.7 +/- 1.6)e-3 ct s^-1	 
  Distance: 126 arcsec from Swift/BAT-GUANO position.
  Flux: (4.42 +/- 0.81)e-13 erg cm^-2 s^-1 (observed, 0.3-10 keV)

Source 3:
  RA (J2000.0):  343.7780  =  22:55:6.71
  Dec (J2000.0): -53.3150  =  -53:18:53.9
  Error: 5.9 arcsec (radius, 90% conf.)
  Count-rate: (2.24 [+1.04, -0.81])e-3 ct s^-1	 
  Distance: 406 arcsec from Swift/BAT-GUANO position.
  Flux: (9.8 [+4.5, -3.5])e-14 erg cm^-2 s^-1 (observed, 0.3-10 keV)

Source 4:
  RA (J2000.0):  343.7223  =  22:54:53.36
  Dec (J2000.0): -53.1215  =  -53:07:17.5
  Error: 5.5 arcsec (radius, 90% conf.)
  Count-rate: (3.18 [+1.21, -0.98])e-3 ct s^-1	 
  Distance: 445 arcsec from Swift/BAT-GUANO position.
  Flux: (1.42 [+0.54, -0.44])e-13 erg cm^-2 s^-1 (observed, 0.3-10 keV)

The source position is 1" away from an AGN candidate (Assef et al,
2018, ApJS, 234, 23; Guo et al., 2018, A&A, 618, 144). 

Source 5:
  RA (J2000.0):  343.6827  =  22:54:43.86
  Dec (J2000.0): -53.1372  =  -53:08:14.1
  Error: 5.8 arcsec (radius, 90% conf. [Enhanced position])
  Count-rate: (5.5 +/- 1.5)e-3 ct s^-1	 
  Distance: 365 arcsec from Swift/BAT-GUANO position.
  Flux: (2.23 +/- 0.59)e-13 erg cm^-2 s^-1 (observed, 0.3-10 keV)

Source 6:
  RA (J2000.0):  343.7423  =  22:54:58.14
  Dec (J2000.0): -53.2260  =  -53:13:33.6
  Error: 7.3 arcsec (radius, 90% conf.)
  Count-rate: (1.62 [+0.86, -0.66])e-3 ct s^-1	 
  Distance: 216 arcsec from Swift/BAT-GUANO position.
  Flux: (7.5 [+4.0, -3.0])e-14 erg cm^-2 s^-1 (observed, 0.3-10 keV)
The source position is 7" away from an AGN candidate (Assef et al,
2018, ApJS, 234, 23). 

Source 7:
  RA (J2000.0):  343.7343  =  22:54:56.22
  Dec (J2000.0): -53.3579  =  -53:21:28.5
  Error: 6.0 arcsec (radius, 90% conf.)
  Count-rate: (2.98 [+1.18, -0.94])e-3 ct s^-1	 
  Distance: 481 arcsec from Swift/BAT-GUANO position.
The source position is 5" away from an AGN candidate (Assef et al,
2018, ApJS, 234, 23). 

Source 8:
  RA (J2000.0):  343.7230  =  22:54:53.51
  Dec (J2000.0): -53.2861  =  -53:17:10.0
  Error: 6.9 arcsec (radius, 90% conf.)
  Count-rate: (2.72 [+1.12, -0.90])e-3 ct s^-1	 
  Distance: 249 arcsec from Swift/BAT-GUANO position.
  Flux: (9.7 [+4.0, -3.2])e-14 erg cm^-2 s^-1 (observed, 0.3-10 keV)
The source position is 9.5" away from an AGN candidate (Assef et al,
2018, ApJS, 234, 23).

Source 9:
  RA (J2000.0):  343.8707  =  22:55:28.96
  Dec (J2000.0): -53.2028  =  -53:12:10.2
  Error: 5.3 arcsec (radius, 90% conf.)
  Count-rate: (2.17 [+1.02, -0.79])e-3 ct s^-1	 
  Distance: 504 arcsec from Swift/BAT-GUANO position.
  Flux: (6.3 [+3.0, -2.3])e-14 erg cm^-2 s^-1 (observed, 0.3-10 keV)

A catalogued source was also detected.

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/00021466.

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