GCN Circular 26728
Subject
Fermi-LAT Gamma-ray Observations of IceCube-200109A and detection of a possible new gamma-ray source, Fermi J1055.8+1034
Date
2020-01-13T09:54:53Z (5 years ago)
From
Simone Garrappa at DESY <simone.garrappa@desy.de>
S. Garrappa (DESY-Zeuthen), S. Buson (Univ. of Wuerzburg) and V. Paliya
(DESY-Zeuthen)�on behalf of the Fermi-LAT collaboration:
We report an analysis of observations of the vicinity of the high-energy
IC200109A neutrino event (GCN 26696) 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 2020-01-09 at 23:41:39.94
UT (T0) with J2000 position RA = 164.49 (+4.94, -4.19) deg, Decl. =
11.87 (+1.16, -1.36) deg 90% PSF containment. Two cataloged >100 MeV
gamma-ray sources (The Fermi-LAT Collaboration 2019,
arXiv:1902.10045)�are located within the 90% IC200109A localization
error. These are the objects 4FGL J1103.0+1157 and 4FGL J1114.6+1225.
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 at gamma-rays.
We searched for the existence of intermediate (months 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 IC200109A 90% best-fit position. Assuming a power-law
spectrum (photon index = 2.0 fixed) for a point source at the IceCube
best-fit position, the >100 MeV flux upper limit (95% confidence) is <
4e-10 ph cm^-2 s^-1 for ~11-years (2008-08-04 / 2020-01-09 UTC), < 8e-9
(< 7e-8) ph cm^-2 s^-1 for a 1-month (1-day) integration time before T0.
Within the error circle for the direction of the neutrino, ~1.2deg
offset from the best-fit IC200109A position, a ~4 sigma excess of gamma
rays, Fermi J1055.8+1034�was detected in an analysis of the integrated
LAT data (> 100 MeV) between 2008-08-04 and �2020-01-09.�Assuming a
power-law spectrum,�the�best-fit�localization is (J2000)
RA:��163.97,�Dec: 10.58 (0.19 deg 99% containment,�0.09 deg
68%�containment), with best-fit spectral parameters flux =�(1.6 +/-
0.8)e-9 ph cm^-2 s^-1 and index = 2.06 +/- 0.18. In a preliminary
analysis of the LAT data over one day and one month prior T0, Fermi
J1055.8+1034� is not significantly detected in the LAT data.
Since Fermi normally operates in an all-sky scanning mode, regular
monitoring of this source will continue. For these sources the Fermi-LAT
contact persons are S. Garrappa (simone.garrappa at desy.de
<http://desy.de/>) and S. Buson (sara.buson at uni-wuerzburg.de
<http://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.