TITLE:   GCN CIRCULAR
NUMBER:  30734
SUBJECT: GRB 210827A: Swift-XRT observations
DATE:    21/08/28 08:58:36 GMT
FROM:    Paolo D'Avanzo at INAF - OAB  <paolo.davanzo@inaf.it>

J. D. Gropp (PSU), J.A. Kennea (PSU), A.P. Beardmore (U. Leicester),
J.P. Osborne (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-GUANO-detected burst GRB 210827A (James DeLaunay et al. GCN
Circ. 30732), collecting 2.3 ks of Photon Counting (PC) mode data
between T0+44.4 ks and T0+50.4 ks. 

One uncatalogued X-ray source has been detected consistent with being
within 296 arcsec of the Swift/BAT-GUANO position, 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):  174.9003  =  11:39:36.07
  Dec (J2000.0): +55.7239  =  +55:43:26.2
  Error: 3.8 arcsec (radius, 90% conf. [Enhanced position])
  Count-rate: 0.0103 +/- 0.0025 ct s^-1   
  Distance: 225 arcsec from Swift/BAT-GUANO position.
  Flux: (4.8 +/- 1.2)e-13 erg cm^-2 s^-1 (observed, 0.3-10 keV)

Four 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/00021461.

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