GCN Circular 26728

S. Garrappa (DESY-Zeuthen), S. Buson (Univ. of Wuerzburg) and V. Paliya 
(DESY-Zeuthen)�on behalf of the Fermi-LAT collaboration:

We report an analysis of observations of the vicinity of the high-energy 
IC200109A neutrino event (GCN 26696
Not found
 
 
) 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 2020-01-09 at 23:41:39.94 
UT (T0) with J2000 position RA = 164.49 (+4.94, -4.19) deg, Decl. = 
11.87 (+1.16, -1.36) deg 90% PSF containment. Two cataloged >100 MeV 
gamma-ray sources (The Fermi-LAT Collaboration 2019, 
arXiv:1902.10045
Not found
 
 
)�are located within the 90% IC200109A localization 
error. These are the objects 4FGL J1103.0+1157 and 4FGL J1114.6+1225. 
Based on a preliminary analysis of the LAT data over the timescales of 
1-day and 1-month prior to T0, these objects are not significantly 
detected at gamma-rays.

We searched for the existence of intermediate (months to years) 
timescale emission from a new gamma-ray transient source. Preliminary 
analysis indicates no significant (> 5 sigma) new excess emission (> 100 
MeV), at the IC200109A 90% best-fit position. Assuming a power-law 
spectrum (photon index = 2.0 fixed) for a point source at the IceCube 
best-fit position, the >100 MeV flux upper limit (95% confidence) is < 
4e-10 ph cm^-2 s^-1 for ~11-years (2008-08-04 / 2020-01-09 UTC), < 8e-9 
(< 7e-8) ph cm^-2 s^-1 for a 1-month (1-day) integration time before T0.

Within the error circle for the direction of the neutrino, ~1.2deg 
offset from the best-fit IC200109A position, a ~4 sigma excess of gamma 
rays, Fermi J1055.8+1034�was detected in an analysis of the integrated 
LAT data (> 100 MeV) between 2008-08-04 and �2020-01-09.�Assuming a 
power-law spectrum,�the�best-fit�localization is (J2000) 
RA:��163.97,�Dec: 10.58 (0.19 deg 99% containment,�0.09 deg 
68%�containment), with best-fit spectral parameters flux =�(1.6 +/- 
0.8)e-9 ph cm^-2 s^-1 and index = 2.06 +/- 0.18. In a preliminary 
analysis of the LAT data over one day and one month prior T0, Fermi 
J1055.8+1034� is not significantly detected in the LAT data.

Since Fermi normally operates in an all-sky scanning mode, regular 
monitoring of this source will continue. For these sources the Fermi-LAT 
contact persons are S. Garrappa (simone.garrappa at desy.de 
<http://desy.de/>) and S. Buson (sara.buson at uni-wuerzburg.de 
<http://uni-wuerzburg.de/>). 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.