GCN Circular 32301
Subject
Fermi-LAT Gamma-ray Observations of IceCube-220627A
Date
2022-06-30T11:26:24Z (2 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
IC220627A neutrino event (GCN 32277) 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 2022-06-27 at 17:51:54.28��
UT (T0) with J2000 position RA = +165.59 (+2.83, -5.61) deg, Decl. =
5.30 (+1.76, -1.33) deg (90% PSF containment). Four cataloged gamma-ray
(>100 MeV) sources are located within the 90% IC220627A localization
region (4FGL-DR3; arXiv:2201.11184; The Fermi-LAT collaboration 2020,
ApJS, 247, 33). Based on a preliminary analysis of the LAT data over the
timescales of 1-month prior to T0, the only source significantly
detected (> 5 sigma) is 4FGL J1040.5+0617, associated with the BL Lac
object GB6 J1040+0617 at z = 0.74 (Paiano et al. 2021, MNRAS, 504, 3).
This object has been previously suggested as candidate counterpart of
the high-energy neutrino event IC141209A (Garrappa et al. 2019, ApJ 880,
2, 103). 4FGL J1040.5+0617 is detected over the timescale of 1-month
prior to T0 at a flux level comparable to the average one reported in
the 4FGL-DR3.
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 IC220627A
best-fit position. Assuming a power-law spectrum (photon index = 2.0
fixed) for a point source at the IC220627A best-fit position, the >100
MeV flux upper limit (95% confidence) is < 2.4e-10 ph cm^-2 s^-1 for
~14-years (2008-08-04 to 2022-06-27 UTC), and < 4.6e-9 (< 4.8e-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 region 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.