GCN Circular 31123
Subject
Fermi-LAT Gamma-ray Observations of IceCube-211123A
Date
2021-11-25T09:57:15Z (3 years ago)
From
Simone Garrappa at DESY <simone.garrappa@desy.de>
S. Garrappa (DESY-Zeuthen), S. Buson (Univ. of Wuerzburg) and R. de
Menezes (Univ. of Wuerzburg, Univ. of Sao Paulo) on behalf of the
Fermi-LAT collaboration:
We report an analysis of observations of the vicinity of the high-energy
IC211123A neutrino event (GCN 31110) 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 2021-11-23 at 14:25:22.6 UT
(T0) with J2000 position RA = 265.52 (+3.14, -2.84) deg, Decl. = 7.33
(+2.38, -2.48) deg (90% PSF containment). Four cataloged gamma-ray (>100
MeV) sources are located within the 90% IC211123A localization region
(4FGL-DR2, The Fermi-LAT collaboration 2020, ApJS, 247, 33). One of
these, 4FGL J1751.5+0938, associated with the BL Lac object OT 081, is
also listed in the 3FHL catalog as 3FHL J1751.5+0938 (Ajello et al.
2017, 232, 18).
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 IC211123A
best-fit position. Assuming a power-law spectrum (photon index = 2.0
fixed) for a point source at the IC211123A best-fit position, the >100
MeV flux upper limit (95% confidence) is < 2.4e-10 ph cm^-2 s^-1 for
~13-years (2008-08-04 to 2021-11-23 UTC), and < 7.4e-9 (< 8.5e-8) 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.