GCN Circular 31845
Subject
Fermi-LAT Gamma-ray Observations of IceCube-220405B
Event
Date
2022-04-07T10:34:33Z (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
IC220405B neutrino event (GCN 31839) 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 2022-04-05 at�� 22:20:03.41��
UT (T0) with J2000 position RA = +320.62 (+1.37, -1.13) deg, Decl. =
29.06 (+0.94, -0.68) deg (90% PSF containment). No cataloged gamma-ray
(>100 MeV) sources are located within the 90% IC220405B localization
region (4FGL-DR3; arXiv:2201.11184; The Fermi-LAT collaboration 2020,
ApJS, 247, 33).
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 IC220405B
best-fit position. Assuming a power-law spectrum (photon index = 2.0
fixed) for a point source at the IC220405B best-fit position, the >100
MeV flux upper limit (95% confidence) is < 3.2e-10 ph cm^-2 s^-1 for
~13-years (2008-08-04 to 2022-04-05 UTC), and < 7.8e-9 (< 1.5e-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 source will continue. For these observations 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.