GCN Circular 29960

J. D. Gropp (PSU), J.A. Kennea (PSU), K.L. Page (U. Leicester), A.P.
Beardmore (U. Leicester), T. Sbarrato (INAF-OAB), P. D'Avanzo
(INAF-OAB), M.G. Bernardini (INAF-OAB), A. Tohuvavohu (U. Toronto) 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-detected burst GRB 210506A (Aaron Tohuvavohu et al. GCN Circ.
29947
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 ), collecting 4.8 ks of Photon Counting (PC) mode data between
T0+29.0 ks and T0+45.6 ks. 

Three uncatalogued X-ray sources have been detected consistent with
being within 296 arcsec of the Swift/BAT position, 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 3:
  RA (J2000.0):  132.9074  =  08:51:37.78
  Dec (J2000.0): +4.5999  =  +04:35:59.6
  Error: 6.4 arcsec (radius, 90% conf.)
  Count-rate: (1.46 [+0.89, -0.69])e-3 ct s^-1	 
  Distance: 206 arcsec from Swift/BAT position.

Source 8:
  RA (J2000.0):  132.8470  =  08:51:23.29
  Dec (J2000.0): +4.6632  =  +04:39:47.4
  Error: 7.4 arcsec (radius, 90% conf.)
  Count-rate: (1.72 [+1.01, -0.78])e-3 ct s^-1	 
  Distance: 291 arcsec from Swift/BAT position.
  Flux: (1.05 [+0.62, -0.48])e-13 erg cm^-2 s^-1 (observed, 0.3-10 keV)

Source 9:
  RA (J2000.0):  132.7917  =  08:51:10.02
  Dec (J2000.0): +4.6042  =  +04:36:15.2
  Error: 7.9 arcsec (radius, 90% conf.)
  Count-rate: (1.76 [+0.96, -0.76])e-3 ct s^-1	 
  Distance: 232 arcsec from Swift/BAT position.
  Flux: (2.8 [+1.5, -1.2])e-13 erg cm^-2 s^-1 (observed, 0.3-10 keV)

Six 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/00021430.

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