[vsnet-grb-info 26840] Fermi-LAT Gamma-ray Observations of IceCube-201120A

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  28943
SUBJECT: Fermi-LAT Gamma-ray Observations of IceCube-201120A
DATE:    20/11/23 00:31:49 GMT
FROM:    Simone Garrappa at DESY  <simone.garrappa at 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 
IC201120A neutrino event (GCN 28927) 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 2020-11-20 at 09:44:40.56 
UT (T0) with J2000 position RA = 307.53 (+5.34 , -5.59) deg, Decl. = 
40.77 (+4.97, -2.80) deg (90% PSF containment). The 90% neutrino 
localization consists in approximately a 85 sqdeg region centered on the 
Galactic plane. Fourteen cataloged gamma-ray (>100 MeV) sources are 
located within the 90% IC201120A localization region (4FGL, The 
Fermi-LAT collaboration 2020, ApJS, 247, 33).

In a preliminary analysis of the LAT data over the timescales of 1-day 
prior to T0, one of these objects is significantly detected (> 5 sigma). 
This is 4FGL J2021.5+4026, associated with the pulsar PSR J2021+4026. 
The estimated daily flux is consistent with the one reported in the 4FGL 
catalog.

Based on a preliminary analysis of the LAT data over the timescales of 
1-month prior to T0, five of these objects are significantly detected (> 
5 sigma). These are 4FGL J2028.6+4110e (associated with the Star Forming 
Region Cygnus-X), 4FGL J2038.4+4212 (associated with the Cygnus Cocoon 
region) and the pulsars 4FGL J2021.5+4026, 4FGL J2030.9+4416 and 4FGL 
J2032.2+4127. The flux values of these objects are consistent with the 
average flux reported in the 4FGL catalog.

We searched for intermediate (day to month) timescale emission from a 
new gamma-ray transient source. Preliminary analysis indicates no 
significant (> 5 sigma) new excess emission (> 100 MeV) at the IC201120A 
best-fit position. Assuming a power-law spectrum (photon index = 2.0 
fixed) for a point source at the IC201120A best-fit position, the >100 
MeV flux upper limit (95% confidence) is < 4.6e-8 (< 3.4e-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.