Swift follow up of IceCube-160731A
ATel #9294; 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)
on 1 Aug 2016; 15:02 UT
Distributed as an Instant Email Notice Transients
Credential Certification: Phil Evans (pae9@star.le.ac.uk)
Subjects: Ultra-Violet, X-ray, Transient
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°. 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-σ 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 4.3×10-13 erg cm-2 s-1 for a typical AGN spectrum (NH=3×1020 cm-2, Γ=1.7). Overlaps between the different tiles accounts for 0.5 square degrees: in these regions the 3-σ upper limit is 0.0071 ct s-1, corresponding to 3.1×10-13 erg cm-2 s-1.
No transient sources were detected in the UVOT data, down to a 3-σ 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
Dec: -00d 38' 16.0"
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
Dec: -01d 08' 45.3"
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
Dec: -00d 01' 50.7"
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
Dec: -00d 36' 00.1"
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
Dec: -00d 06' 45.6"
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
Dec: -00d 06' 45.6"
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.
