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GCN Circular 31680

Subject
Fermi-LAT Gamma-ray Observations of IceCube-220303A
Date
2022-03-04T19:04:06Z (2 years ago)
From
Simone Garrappa at DESY <simone.garrappa@desy.de>
S. Garrappa (DESY-Zeuthen), S. Buson (Univ. of Wuerzburg) and J. 
Sinapius (DESY-Zeuthen) on behalf of the Fermi-LAT collaboration:

We report an analysis of observations of the vicinity of the high-energy 
IC220303A neutrino event (GCN 31670) 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 2022-03-03 18:00:07.62 UTC 
(T0) with J2000 position RA = 267.80 (+1.50, -1.17) deg, Decl. = 11.42 
(+0.89, -1.14) deg 90% PSF containment. No cataloged gamma-ray sources 
are found within the 90% IC220303A localization error (4FGL-DR3; 
arXiv:2201.11184; The Fermi-LAT collaboration 2020, ApJS, 247, 33).

We searched for the existence of intermediate (months to years) 
timescale emission from a new gamma-ray transient source. Preliminary 
analysis indicates no significant (>5sigma) new excess emission (> 100 
MeV) within the IC220303A 90% confidence localization. Assuming a 
power-law spectrum (photon index = 2.0 fixed) for a point source at the 
IC220303A best-fit position, the >100 MeV flux upper limit (95% 
confidence) is < 5.6-10 ph cm^-2 s^-1 for ~13-years (2008-08-04 to 
2022-03-03 UTC), <4.6-9 (< 6.6-8) ph cm^-2 s^-1 for a 1-month (1-day) 
integration time before T0.

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