GCN Circular 20125

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-161103
utilising the on-board 19-point tiling pattern to cover a region centred
on RA,Dec (J2000) = (40.874,+12.616), with a radius of approximately 0.8 
degrees. Swift-XRT collected between 150 and 250 s of PC mode data per 
tile. The observations were taken between 13:58:30 and 18:55:15 UT on 
2016 November 3 (i.e. from 17.5 ks to 35.3.5 ks after the neutrino 
trigger), and covered 2.1 square degrees.

Four X-ray sources are detected in the observations. None of these are
known X-ray emitters, however all are faint, and well below the RASS 
limits, therefore we do not consider any of them to be likely 
counterparts to the IceCube trigger.

The 3-sigma upper limit on the count rate in the rest of the field 
ranges is 0.03 ct s^-1, which corresponds to a 0.3-10 keV flux of 
1.2e-12 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 0.02 ct
s^-1, corresponding to 8.1e-13 erg cm^-2 s^-1.

Details of the four detected X-ray sources are below. All fluxes are
0.3-10 keV and assume the same AGN spectrum as above.

Source 1
========
RA:          02h 42m 42.34s = 40.6764d
Dec:         +12d 09' 40.1" = 12.1611d
Error:       3.5 arcsec (90% confidence radius)
Count rate:  (3.9 [+1.7, -1.3]) x 10^-2 ct s^-1
Flux:        (1.6 [+0.7, -0.5]) x 10^-12 erg cm^-2 s^-1


Source 2
========
RA:          02h 44m 51.43s = 41.2143d
Dec:         +12d 57' 23.3" = 12.9565d
Error:       6.4 arcsec (90% confidence radius)
Count rate:  (3.8 [+1.8, -1.4]) x 10^-2 ct s^-1
Flux:        (1.5 [+0.7, -0.6]) x 10^-12 erg cm^-2 s^-1

Source 3
========
RA:          02h 44m 51.43s = 41.6322d
Dec:         +12d 34' 09.1" = 12.5692d
Error:       3.7 arcsec (90% confidence radius)
Count rate:  (3.5 [+1.9, -1.4]) x 10^-2 ct s^-1
Flux:        (1.4 [+0.7, -0.6]) x 10^-12 erg cm^-2 s^-1

Source 4
========
RA:          02h 46m 07.42s = 41.5309d
Dec:         +12d 44' 11.3" = 12.7365d
Error:       3.0 arcsec (90% confidence radius)
Count rate:  (3.8 [+1.8, -1.4]) x 10^-2 ct s^-1
Flux:        (1.5 [+0.7, -0.6]) x 10^-12 erg cm^-2 s^-1