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GCN Circular 23031

Subject
GRB 180718B: Swift-XRT observations
Date
2018-07-24T14:21:22Z (7 years ago)
From
Boris Sbarufatti at PSU <bxs60@psu.edu>
B. Sbarufatti (INAF-OAB/PSU), A. A. Breeveld (UCL-MSSL), Z. Liu (NAOC /
U. Leicester), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester),
A. Melandri (INAF-OAB), P. D'Avanzo (INAF-OAB), V. D'Elia (ASDC), D.N.
Burrows (PSU), A. Tohuvavohu (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 180718B (Crnogorcevic et al. GCN Circ.
22961Loading...
 
 ), collecting 5.0 ks of Photon Counting (PC) mode data between
T0+38.9 ks and T0+50.6 ks. 

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. The UVOT finds no new optical sources at the position of any
of the four X-ray sources. Details of these sources are given below:

Source 1:
  RA (J2000.0):  44.7960  =  02:59:11.03
  Dec (J2000.0): -31.6692  =  -31:40:09.2
  Error: 3.0 arcsec (radius, 90% conf. [Enhanced position])
  Count-rate: (9.0 +/- 2.4)e-3 ct s^-1	 
  Distance: 705 arcsec from Fermi/LAT position.
  Flux: (2.79 +/- 0.74)e-13 erg cm^-2 s^-1 (observed, 0.3-10 keV)

Source 2:
  RA (J2000.0):  44.6153  =  02:58:27.68
  Dec (J2000.0): -31.6555  =  -31:39:19.9
  Error: 6.1 arcsec (radius, 90% conf.)
  Count-rate: (1.91 [+0.92, -0.71])e-3 ct s^-1	 
  Distance: 593 arcsec from Fermi/LAT position.
  Flux: (5.1 [+2.4, -1.9])e-14 erg cm^-2 s^-1 (observed, 0.3-10 keV)

Source 3:
  RA (J2000.0):  44.7970  =  02:59:11.27
  Dec (J2000.0): -31.4797  =  -31:28:47.0
  Error: 4.0 arcsec (radius, 90% conf. [Enhanced position])
  Count-rate: (2.80 [+1.14, -0.91])e-3 ct s^-1	 
  Distance: 366 arcsec from Fermi/LAT position.
  Flux: (1.19 [+0.49, -0.39])e-13 erg cm^-2 s^-1 (observed, 0.3-10 keV)


Source 4:
  RA (J2000.0):  44.7053  =  02:58:49.28
  Dec (J2000.0): -31.4407  =  -31:26:26.5
  Error: 5.0 arcsec (radius, 90% conf.)
  Count-rate: (2.51 [+1.10, -0.87])e-3 ct s^-1	 
  Distance: 227 arcsec from Fermi/LAT position.
  Flux: (5.1 [+2.2, -1.8])e-14 erg cm^-2 s^-1 (observed, 0.3-10 keV)

The results of the XRT-team automatic analysis of the XRT observations,
including a position-specific upper limit calculator, are available at
http://www.swift.ac.uk/ToO_GRBs/00020803.

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