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GCN Circular 22953

Subject
GRB 180715A: Swift-XRT observations
Date
2018-07-16T23:29:17Z (6 years ago)
From
Phil Evans at U of Leicester <pae9@leicester.ac.uk>
J.A. Kennea (PSU), B. Sbarufatti (INAF-OAB/PSU), S.L. Gibson (U.
Leicester), Z. Liu (NAOC / U. Leicester), J.P. Osborne (U. Leicester),
A. D'Ai (INAF-IASFPA), A. Melandri (INAF-OAB), P. D'Avanzo (INAF-OAB),
D.N. Burrows (PSU) and T. N. Ukwatta (LANL) report on behalf of the
Swift-XRT team:

We have analysed 14 ks of Photon Counting (PC) mode XRT data for the
Swift/BAT-detected burst GRB 180715A (Ukwatta et al. GCN Circ. 22951),
collected between T0+11.0 ks and T0+67.7 ks. 

Five 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.


The 3-sigma upper limit at the BAT position is 9.5x10^-4 ct/sec.

Details of these sources are given below:

Source 5:
  RA (J2000.0):  235.1362  =  15:40:32.68
  Dec (J2000.0): -0.9559  =  -00:57:21.2
  Error: 6.1 arcsec (radius, 90% conf.)
  Count-rate: (5.4 [+2.7, -2.1])e-4 ct s^-1   
  Distance: 266 arcsec from Swift/BAT position.

Source 7:
  RA (J2000.0):  235.0967  =  15:40:23.21
  Dec (J2000.0): -0.9760  =  -00:58:33.6
  Error: 5.4 arcsec (radius, 90% conf.)
  Count-rate: (7.4 [+3.2, -2.6])e-4 ct s^-1   
  Distance: 210 arcsec from Swift/BAT position.

Source 8:
  RA (J2000.0):  235.1256  =  15:40:30.15
  Dec (J2000.0): -0.8791  =  -00:52:44.8
  Error: 6.5 arcsec (radius, 90% conf.)
  Count-rate: (8.2 [+3.3, -2.7])e-4 ct s^-1   
  Distance: 261 arcsec from Swift/BAT position.
  Flux: (5.6 [+2.3, -1.8])e-14 erg cm^-2 s^-1 (observed, 0.3-10 keV)

Source 10:
  RA (J2000.0):  234.9980  =  15:39:59.51
  Dec (J2000.0): -0.9504  =  -00:57:01.5
  Error: 5.0 arcsec (radius, 90% conf.)
  Count-rate: (1.85 [+0.46, -0.42])e-3 ct s^-1	 
  Distance: 272 arcsec from Swift/BAT position.
  Flux: (8.9 [+2.2, -2.0])e-14 erg cm^-2 s^-1 (observed, 0.3-10 keV)

Source 11:
  RA (J2000.0):  235.0291  =  15:40:6.98
  Dec (J2000.0): -0.9196  =  -00:55:10.6
  Error: 10.7 arcsec (radius, 90% conf.)
  Count-rate: (4.4 [+2.5, -2.0])e-4 ct s^-1   
  Distance: 144 arcsec from Swift/BAT position.

Ten 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
http://www.swift.ac.uk/ToO_GRBs/00848048.

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