TITLE:   GCN CIRCULAR
NUMBER:  26700
SUBJECT: IceCube-200109A: Swift-XRT and UVoT Follow-up Observations
DATE:    20/01/10 22:39:51 GMT
FROM:    Azadeh Keivani at Columbia U  <azadeh.keivani@columbia.edu>

IceCube-200109A: Swift-XRT and UVoT Follow-up Observations

P. A. Evans (U. Leicester), A. Keivani (Columbia U.), J. A. Kennea (PSU),
F. E. Marshall (NASA/GSFC), and D. B. Fox (PSU), report:

The Neil Gehrels Swift Observatory observed the field of the IceCube
Astrotrack Gold astrophysical neutrino candidate event IceCube-200109A
(revision 1, https://gcn.gsfc.nasa.gov/gcn3/26696.gcn3) beginning Jan 10,
05:55:10 UT (~6 hours after the neutrino arrival time).

Swift utilized a 35-point tiling pattern to cover a region centered on
R.A., Dec. (J2000) = 164.49d, 11.87d, with a radius of approximately 66
arcmin; estimated 90%-containment error region for this event is rather
large with asymmetric (+4.94d, -4.19d) on RA and (+1.16, -1.36) on Dec.
Swift-XRT collected ~230 s per field of PC-mode data per tile (except for
one tile which only 8 s were obtained). The X-ray data have been reduced
using the analysis approach and software routines of Evans et al. 2014
(ApJS, 210, 8).

Only one X-ray source (RA = 165.34231 deg, Dec = 12.58648 deg) is detected
in the field of observation, which is consistent with a double or multiple
star (HEI 155; 1.5 arcsec away) which is also 18.8 arcsec away from a known
X-ray source 1RXS J110123.1+123524 from ROSAT/RASSFSC. This is not
considered as a source of interest.

Excluding the identified source, the 3-sigma upper limit on the count rate
of any point-like counterpart over the rest of the tiled region 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).

Swift/UVOT co-observed with XRT (with a slightly smaller field-of-view)
using the U filter. The exposures are ~219 s except for one tile (target ID
00013102), for which only 8 s were obtained. No uncatalogued sources were
found with a limiting magnitude of about 18.9 for the typical field and
17.5 for target ID 00013102.