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
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.