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GCN Circular 33587

Fermi-LAT gamma-ray observations of IceCube-230405A
2023-04-07T16:59:55Z (a year ago)
Simone Garrappa at DESY <>
S. Garrappa (Ruhr-Universitaet Bochum), J. Sinapius (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 IC230405A�� 
high-energy neutrino event (GCN 33567) 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 2023-04-05 at 13:20:20.04 
UT (T0) with J2000 position RA = 120.85 (+2.86, -4.98) deg, Decl. = 
+9.75 (+1.87, -2.17) deg (90% PSF containment).�� Seven cataloged 
gamma-ray (>100 MeV; The Fermi-LAT collaboration 2022, ApJS, 260, 53) 
sources are located within the 90% IC230405A�� localization region. Based 
on a preliminary analysis of the LAT data over a month and day timescale 
prior T0, these objects are not significantly detected at gamma rays.

We searched for intermediate (days 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 IC230405A 
best-fit position. Assuming a power-law spectrum (photon index = 2.0 
fixed) for a point source at the IC230405A best-fit position, the >100 
MeV flux upper limit (95% confidence) is < 1.8e-10 ph cm^-2 s^-1 for 
~14-years (2008-08-04 to 2023-04-05 UTC), and < 9.4e-9 (<1.7e-7) 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 region will continue. For these observations the 
Fermi-LAT contact persons are S. Garrappa (simone.garrappa at, J. Sinapius (jonas.sinapius at and S. 
Buson (sara.buson at

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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