GCN Circular 19747
Subject
Swift follow up of IceCube-160731A
Date
2016-08-01T15:00:23Z (8 years ago)
From
Phil Evans at U of Leicester <pae9@leicester.ac.uk>
P.A. Evans (U. Leicester), J.A. Kennea (PSU), A. Keivani (PSU), D.B. Fox
(PSU), G. Tesic (PSU), D.F. Cowen (PSU), J.P. Osborne (U. Leicester),
M.W.E. Smith (JPL) and F.E. Marshall (GSFC) report on behalf of the
Swift-IceCube collaboration:
Swift has observed the field of the IceCube HESE event IceCube-160731A,
"AMON ICECUBE HESE 128290 6888376" (revision 0), utilising the on-board
19-point tiling pattern to cover a region centred on RA,Dec (J2000) =
(215.109, -0.458), with a radius of approximately 0.8 degrees. Swift-XRT
collected ~800 s per field of PC mode data per tile. The observations
were taken between 03:00:46 and 14:51:52 on 2016 Jul 31 (i.e. from
3.9 ks to 46.5 ks after the neutrino trigger), and covered 2.1
square degrees.
Six X-ray sources are detected in the observations. All of these
correspond either to known X-ray emitters, or to objects catalogued
(e.g. in SIMBAD) and from which X-rays may be expected. Therefore, we
conclude that we have not discovered a transient X-ray event associated
with the IceCube trigger. The 3-sigma upper limit on the count rate in
the rest of the field is 0.01 ct s^-1, which corresponds to a 0.3-10 keV
flux of 4.3e-13 erg cm^-2 s^-1 for a typical AGN spectrum (NH=3e20
cm^-2, Gamma=1.7). Overlaps between the different tiles accounts for 0.5
square degrees: in these regions the 3-sigma upper limit is 0.0071 ct
s^-1, corresponding to 3.1e-13 erg cm^-2 s^-1.
No transient sources were detected in the UVOT data, down to a 3-sigma
upper limit of 18.0, in the u filter.
Details of the six detected X-ray sources are below. All fluxes are
0.3-10 keV and assume the same AGN spectrum as above.
Source 1
========
RA: 14h 22m 46.57s = 215.69403d
Dec: -00d 38' 16.0" = -0.63777d
Error: 4.2 arcsec (90% confidence radius)
Count rate: (1.7 +/- 0.4) x 10^-2 ct s^-1
Flux: (7.3 +/- 1.7) x 10^-13 erg cm^-2 s^-1
Notes: This source is 2.4" from HD 125981 which SIMBAD lists as an
A0IV star (classified by the Michigan Spectral Survey).
This detection may not be due to an X-ray source, but due
to the bright (V = 6.7) stellar optical flux.
Source 2
========
RA: 14h 19m 36.50s = 214.90209d
Dec: -01d 08' 45.3" = -0.14592d
Error: 4.9 arcsec (90% confidence radius)
Count rate: (1.3 +/- 0.6) x 10^-2 ct s^-1
Flux: (5.6 +/- 2.6) x 10^-13 erg cm^-2 s^-1
Notes: This source is 6.5" from [VV2006] J141936.0-010840 which
SIMBAD lists as a quasar.
Source 3
========
RA: 14h 22m 53.44s = 215.72267d
Dec: -00d 01' 50.7" = -0.03074d
Error: 5.9 arcsec (90% confidence radius)
Count rate: (2.2 +/- 0.7) x 10^-2 ct s^-1
Flux: (9.5 +/- 3.0) x 10^-13 erg cm^-2 s^-1
Notes: This source is 2.2" from QSO J1422-0001 which SIMBAD lists
as a quasar, and 3.1" from the known X-ray source,
3XMM J142253.3-000149. The observed X-ray flux is
consistent with the flux in the 3XMM catalogue.
Source 4
========
RA: 14h 22m 53.44s = 215.72267d
Dec: -00d 36' 00.1" = -0.60004d
Error: 8.1 arcsec (90% confidence radius)
Count rate: (6.7 +/- 3.2) x 10^-3 ct s^-1
Flux: (2.9 +/- 1.4) x 10^-13 erg cm^-2 s^-1
Notes: This source has been previously detected by Swift
(1SXPS J142252.8-003553) and the observed flux is
consistent with the catalogued values.
Source 5
========
RA: 14h 19m 50.15s = 214.95898
Dec: -00d 06' 45.6" = -0.11266d
Error: 5.5 arcsec (90% confidence radius)
Count rate: (1.5 +/- 0.6) x 10^-2 ct s^-1
Flux: (6.5 +/- 2.6) x 10^-13 erg cm^-2 s^-1
Notes: This source is 2.3" from [VV2006] J141949.9-000644 which
SIMBAD lists as a quasar.
Source 6
========
RA: 14h 19m 50.15s = 214.61169d
Dec: -00d 06' 45.6" = 0.24144d
Error: 6.6 arcsec (90% confidence radius)
Count rate: (1.5 +/- 0.7) x 10^-2 ct s^-1
Flux: (6.5 +/- 3.0) x 10^-13 erg cm^-2 s^-1
Notes: This source is 2.3" from 2MASS J14182661+0014283, which
appears to be a late-type star.