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 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.