TITLE:   GCN CIRCULAR
NUMBER:  21133
SUBJECT: GRB 170522A: Swift-XRT observations
DATE:    17/05/24 13:51:04 GMT
FROM:    Sarah Gibson at U.of Leicester  <slg44@leicester.ac.uk>

B. Mingo (U. Leicester), A.P. Beardmore (U. Leicester), A. Melandri
(INAF-OAB), P. D'Avanzo (INAF-OAB), V. D'Elia (ASDC), J.A. Kennea
(PSU), B. Sbarufatti (INAF-OAB/PSU), D.N. Burrows (PSU) and P.A. Evans
(U. Leicester) report on behalf of the Swift-XRT team:

Swift-XRT has performed follow-up observations of the
Fermi/LAT-detected burst GRB 170522A (Arimoto et al. GCN Circ. 21127)
in a series of observations tiled on the sky. The total exposure time
is 4.7 ks, distributed over 5 tiles; the maximum exposure at a single
sky location was 3.3 ks. The data were collected between T0+39.4 ks and
T0+51.3 ks, and are entirely in Photon Counting (PC) mode. 

Four 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 1:
  RA (J2000.0):  139.1534  =  09:16:36.82
  Dec (J2000.0): +25.4844  =  +25:29:03.9
  Error: 3.8 arcsec (radius, 90% conf. [Enhanced position])
  Count-rate: (9.7 [+3.1, -2.6])e-3 ct s^-1   
  Distance: 901 arcsec from Fermi/LAT position.
  Flux: (4.2 [+1.3, -1.1])e-13 erg cm^-2 s^-1 (observed, 0.3-10 keV)

Source 2:
  RA (J2000.0):  139.2381  =  09:16:57.13
  Dec (J2000.0): +25.4737  =  +25:28:25.5
  Error: 6.0 arcsec (radius, 90% conf.)
  Count-rate: (6.7 [+3.3, -2.5])e-3 ct s^-1   
  Distance: 780 arcsec from Fermi/LAT position.
  Flux: (4.4 [+2.2, -1.6])e-13 erg cm^-2 s^-1 (observed, 0.3-10 keV)

Source 3:
  RA (J2000.0):  139.1099  =  09:16:26.38
  Dec (J2000.0): +25.8756  =  +25:52:32.2
  Error: 6.5 arcsec (radius, 90% conf.)
  Count-rate: (6.6 [+2.9, -2.2])e-3 ct s^-1   
  Distance: 1050 arcsec from Fermi/LAT position.

Source 4:
  RA (J2000.0):  139.0535  =  09:16:12.85
  Dec (J2000.0): +25.6179  =  +25:37:04.5
  Error: 10.2 arcsec (radius, 90% conf.)
  Count-rate: (5.6 [+3.1, -2.3])e-3 ct s^-1   
  Distance: 948 arcsec from Fermi/LAT position.

The results of the XRT-team automatic analysis of the tiled XRT
observations, including a position-specific upper limit calculator, are
available at http://www.swift.ac.uk/xrt_products/TILED_GRB00068.

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