GCN Circular 28519
Subject
Fermi-LAT Gamma-ray Observations of IceCube-200926B
Date
2020-09-28T12:15:54Z (5 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
IC200926B neutrino event (GCN 28509) 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 2020-09-26 at 22:35:29.22�
UT (T0) with J2000 position RA = 184.75 (+3.64, -1.55) deg, Decl. =
32.93 (+1.15, -0.91) 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% IC200926B
localization error.
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 IC200926B
best-fit position. Assuming a power-law spectrum (photon index = 2.0
fixed) for a point source at the IC200926B best-fit position, the >100
MeV flux upper limit (95% confidence) is < 1.4e-10 ph cm^-2 s^-1 for
~12-years (2008-08-04 / 2020-09-26 UTC), < 6.6e-9 (<1e-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.