GCN Circular 22132

S. Buson (NASA/GSFC), M. Kreter (Wurzburg Univ.), 
D. Kocevski (NASA/MSFC) report on behalf of the Fermi-LAT collaboration 


We report follow-up observations of the [very] high-energy IceCube-171106A 
neutrino event (GCN #22105) with all-sky survey data from the Large Area 
Telescope (LAT), on board the Fermi Gamma-ray Space Telescope. The IceCube 
event was detected on 2017-1-06 18:39:39.21 UTC (T0) with J2000 position
RA =340.25 deg, Dec = 7.314 deg (14.99 arcmin 50% containment). The closest 
cataloged >100 MeV gamma-ray source is 3FGL J2234.8+0945, at a distance of 
roughly 2.9 deg.  The source is associated with the pulsar PSR J2234+0944.


We searched for the existence of intermediate (days to months) timescale 
emission from a new gamma-ray transient source [or excess emission from a 
known catalog source]. Preliminary analysis indicates no significant excess 
gamma-ray emission (0.1 - 300 GeV) within the IceCube-171106A 50% confidence 
localisation. Assuming a power-law spectrum (photon index = 2.2 fixed) for a point 
source at the IceCube position, the >100 MeV photon flux upper limits 
(95% confidence) are  < 2.0 x 10^-7 ph cm^-2 s^-1 in one day of exposure
prior to T0, and < 3.4 x 10^-8 ph cm^-2 s^-1 in one week of exposure prior to T0, 
and < 1.8 x 10^-9 ph cm^-2 s^-1 in eight months of exposure prior to T0. 


Swift-XRT follow up observations of the IceCube-171106A field by
Keivani et al (GCN #22115) reported the detection of several X-ray sources.
Integrating the LAT data for the time intervals aforementioned, no significant
gamma-ray emission is observed consistent with these sources.


Because Fermi operates in an all-sky scanning mode, regular gamma-ray
monitoring of this source region will continue. For this source the Fermi LAT 
contact person is S. Buson (email: sara.buson at nasa.gov).


The Fermi LAT is a pair conversion telescope designed to cover the energy
band from 20 MeV to greater than 300 GeV. It is the product of an international 
collaboration between NASA and DOE in the U.S. and many scientific institutions
across France, Italy, Japan and Sweden.