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GCN Circular 28438

Subject
Fermi-LAT Gamma-ray Observations of IceCube-200916A
Date
2020-09-17T13:37:29Z (4 years ago)
From
Simone Garrappa at DESY <simone.garrappa@desy.de>
S. Garrappa (DESY-Zeuthen) and S. Buson (Univ. of Wuerzburg) on behalf 
of the Fermi-LAT collaboration:

We report an analysis of observations of the vicinity of the high-energy 
IC200916A neutrino event (GCN 28433) 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 2020-09-16 20:40:30.95 UTC 
(T0) with J2000 position RA = 109.78 (-1.44,+1.08) deg, Decl. = 14.36 
(-0.85,+0.88) deg 90% PSF containment.�No cataloged >100 MeV gamma-ray 
sources (The Fourth Fermi-LAT catalog; The Fermi-LAT collaboration 2020, 
ApJS, 247, 33) are located within the 90% IC200916A localization error.

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 (0.1 - 
800 GeV) within the IC200916A 90% confidence localization. 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 < 5.6e-10 ph cm^-2 s^-1 for ~12-years (2008-08-04 / 
2019-09-16 UTC), < 1e-8 (< 5e-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 these observations 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.
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