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GCN Circular 33248

Subject
Fermi-LAT gamma-ray observations of IceCube-230201A
Date
2023-02-01T20:41:13Z (a year ago)
From
Sara Buson at GSFC/Fermi <sara.buson@gmail.com>
J. Sinapius (DESY-Zeuthen), S. Garrappa (Ruhr-Universitaet Bochum) and S.
Buson (Univ. of Wuerzburg) on behalf of the Fermi-LAT collaboration:

We report an analysis of observations of the vicinity of the IC230201A
high-energy neutrino event (GCN 33244) 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 2023-02-01 at 06:20:54.42 UT (T0) with
J2000 position RA = 345.41 (+2.50, -3.07) deg, Decl. = +12.10 (+1.62,
-1.53) deg (90% PSF containment). Three cataloged gamma-ray (>100 MeV; The
Fermi-LAT collaboration 2022, ApJS, 260, 53) sources are located within the
90% IC230201A  localization region. 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 (> 5 sigma).

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 IC230201A best-fit
position. Assuming a power-law spectrum (photon index = 2.0 fixed) for a
point source at the IC230201A best-fit position, the >100 MeV flux upper
limit (95% confidence) is < 2.8e-10 ph cm^-2 s^-1 for ~14-years (2008-08-04
to 2023-02-01 UTC), and < 3.6e-9 (<2.4e-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
ruhr-uni-bochum.de), J. Sinapius (jonas.sinapius 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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