{
  "bibcode": "2022GCN.31701....1G",
  "body": "S. Garrappa (DESY-Zeuthen), S. Buson (Univ. of Wuerzburg) and J. \nSinapius (DESY-Zeuthen) on behalf of the Fermi-LAT collaboration:\n\nWe report an analysis of observations of the vicinity of the high-energy \nIC220304A neutrino event (GCN 31679) with data from the Large Area \nTelescope (LAT), on board the Fermi Gamma-ray Space Telescope. The \nIceCube event was detected on 2022-03-04 17:44:12.21 UTC (T0) with J2000 \nposition RA = 48.78 (+7.68, -6.24) deg, Decl. = 4.48 (+5.91, -4.96) deg \n90% PSF containment. Several cataloged gamma-ray sources are found \nwithin the 90% IC220304A localization error (4FGL-DR3; arXiv:2201.11184; \nThe Fermi-LAT collaboration 2020, ApJS, 247, 33). Based on a preliminary \nanalysis of the LAT data over a 1-day integration time before T0, these \nsources are not significantly detected.\n\nBased on a preliminary analysis of the LAT data over a 1-month \nintegration time before T0, two cataloged LAT sources within the 90% \nIC220304A localization error are significantly (>5 sigma) detected. One \nis 4FGL J0313.0+0229, located ~2 deg from the neutrino best-fit \nlocalization and associated with the blazar of uncertain type TXS \n0310+022. This source is detected with an average monthly flux of�� (1.1 \n+/- 0.2)e-7 ph cm^-2 s^-1 and photon index of 2.13 +/- 0.09. This flux \nvalue is ~20 times the value reported in the 4FGL-DR3, and the photon \nindex is significantly smaller than the 4FGL-DR3 value of 2.48 +/- 0.08. \nAn inspection of the one-month-binned light curve indicates that 4FGL \nJ0313.0+0229 entered an elevated state roughly at the end of 2019 (also \nATel#13463). The second object is the unidentified source 4FGL \nJ0259.0+0552, located ~4.2 deg from the neutrino best-fit localization. \nThe current average monthly flux is�� (4 +/- 2)e-8 ph cm^-2 s^-1 (~10 \ntimes the 4FGL flux). The observed photon index of 2.1 +/- 0.2 is \nconsistent with the 4FGL-DR3 value of 2.00 +/- 0.05. An inspection of \nthe one-month-binned light curve of 4FGL J0259.0+0552 does not indicate \nany remarkable activity during the decade-long Fermi-LAT monitoring.\n\nWe searched for the existence of intermediate (day to months) timescale \nemission from a new gamma-ray transient source. Preliminary analysis \nindicates no significant (>5sigma) new excess emission within the \nIC220304A 90% confidence localization. Assuming a power-law spectrum \n(photon index = 2.0 fixed) for a point source at the IC220304A best-fit \nposition, the >100 MeV flux upper limit (95% confidence) is < 1.2e-10 ph \ncm^-2 s^-1 for ~13-years (2008-08-04 to 2022-03-04 UTC), <1.2e-8 (< \n1.8e-7) ph cm^-2 s^-1 for a 1-month (1-day) integration time before T0.\n\n\nSince Fermi normally operates in an all-sky scanning mode, regular \nmonitoring of this source will continue. For this source the Fermi-LAT \ncontact persons are S. Garrappa (simone.garrappa at desy.de) and S. \nBuson (sara.buson at uni-wuerzburg.de).\n\n\nThe Fermi LAT is a pair conversion telescope designed to cover the \nenergy band from 20 MeV to greater than 300 GeV. It is the product of an \ninternational collaboration between NASA and DOE in the U.S. and many \nscientific institutions across France, Italy, Japan and Sweden.",
  "circularId": 31701,
  "createdOn": 1646605032000,
  "email": "simone.garrappa@desy.de",
  "subject": "Fermi-LAT Gamma-ray Observations of IceCube-220304A",
  "submitter": "Simone Garrappa at DESY  <simone.garrappa@desy.de>",
  "eventId": "IceCube-220304A"
}