{
  "bibcode": "2022GCN.32478....1G",
  "body": "S. Garrappa (DESY-Zeuthen) and S. Buson (Univ. of Wuerzburg) on behalf \nof the Fermi-LAT collaboration:\n\nWe report an analysis of observations of the vicinity of the high-energy \nIC220822A neutrino event (GCN 32475) with all-sky survey data from the \nLarge Area Telescope (LAT), on board the Fermi Gamma-ray Space \nTelescope. The IceCube event was detected on 2022-08-22 at 20:26:30.03�� \nUT (T0) with J2000 position RA = +273.08 (+2.47, -2.50) deg, Decl. = \n21.54 (+0.94, -1.18) deg (90% PSF containment). Two cataloged gamma-ray \n(>100 MeV) sources are located within the 90% IC220822A localization \nregion (4FGL-DR3; arXiv:2201.11184; The Fermi-LAT collaboration 2020, \nApJS, 247, 33). These are 4FGL J1809.3+2042 associated with the BL Lac \nRX J1809.3+2041 and 4FGL J1819.1+2133, associated with the BL Lac MG2 \nJ181902+2132 at 1.1 deg and 1.6 deg distance from the best-fit neutrino \nlocalization, respectively. Based on a preliminary analysis of the LAT \ndata over the timescales of 1-day and 1-month prior to T0, these objects \nare not significantly detected (> 5 sigma).\n\nWe searched for intermediate (days to years) timescale emission from a \nnew gamma-ray transient source. Preliminary analysis indicates no \nsignificant (> 5 sigma) new excess emission (> 100 MeV) at the IC220822A \nbest-fit position. Assuming a power-law spectrum (photon index = 2.0 \nfixed) for a point source at the IC220822A best-fit position, the >100 \nMeV flux upper limit (95% confidence) is < 2e-10 ph cm^-2 s^-1 for \n~14-years (2008-08-04 to 2022-08-22 UTC), and < 4.1e-9 (<8.8e-8) ph \ncm^-2 s^-1 for a 1-month (1-day) integration time before T0.\n\nWithin the 90% confidence localization of the neutrino, 0.6 deg offset \nfrom the best-fit IC220822A position, an excess of gamma rays, Fermi \nJ1810.1+2154, was detected in an analysis of the ~14-years integrated \nLAT data (100 MeV - 1 TeV) prior to T0. This putative new source is \ndetected at a statistical significance ~4.5 sigma (calculated following \nthe prescription adopted in the The Fourth Fermi-LAT catalog, The \nFermi-LAT collaboration 2020, ApJS, 247, 33). Assuming a power-law \nspectrum, the excess has best-fit localization of RA = 272.54 deg, Decl. \n= 21.91 deg (95% containment radius = 0.14 deg) with best-fit spectral \nparameters, flux = (6.6 +/- 4.7)e-10 ph cm^-2 s^-1, index = 1.9 +/-0.2. \nIn a preliminary analysis of the LAT data over one month prior to T0, \nFermi J1810.1+2154 is not significantly detected in the LAT data. All \nvalues include the statistical uncertainty only.\n\nSince Fermi normally operates in an all-sky scanning mode, regular \nmonitoring of this region will continue. For these observations the \nFermi-LAT contact persons are S. Garrappa (simone.garrappa at desy.de) \nand S. Buson (sara.buson at uni-wuerzburg.de).\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": 32478,
  "createdOn": 1661291057000,
  "email": "simone.garrappa@desy.de",
  "subject": "Fermi-LAT gamma-ray observations of IceCube-220822A and detection of a new gamma-ray source, Fermi J1810.1+2154",
  "submitter": "Simone Garrappa at DESY  <simone.garrappa@desy.de>",
  "eventId": "IceCube-220822A"
}