GCN Circular 27544
Subject
Fermi-LAT Gamma-ray Observations of IceCube-200410A
Date
2020-04-11T23:23:10Z (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
IC200410A neutrino event (GCN 27534) 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 2020-04-10 at 23:19:55.49
UT (T0) with J2000 position RA = 242.58 (+14.05, -13.35) deg, Decl. =
11.61 (+7.87, -6.21) deg 90% PSF containment. Several cataloged >100 MeV
gamma-ray sources (The Fermi-LAT Collaboration 2019,
arXiv:1902.10045)�are located within the 90% IC200410A localization
error. Based on a preliminary analysis of the LAT data over the
timescales of 1-day prior to T0, these objects are not significantly
detected at gamma-rays. Two of these objects are significantly detected
over the timescale of 1-month prior to T0, these are 4FGL J1548.3+1456
(associated with the BL Lac�object�NVSS J154824+145702) and 4FGL
J1555.7+1111 (associated with the BL Lac object�PG 1553+113). Based on a
preliminary analysis at this timescale, both objects show a gamma-ray
flux comparable to the catalog value.
We searched for the existence of intermediate (months to years)
timescale emission from a new gamma-ray transient source. Preliminary
analysis indicates no significant (>5sigma) new excess emission (> 100
MeV) within the IC200410A 90% confidence localization. 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 < 1e-8 (< 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 this source 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.