{
  "bibcode": "2020GCN.28481....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 \nIC200921A neutrino event (GCN 28468) 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 2020-09-21 19:07:12.89 UT \n(T0) with J2000 position RA = 195.29 (+2.35, -1.73) deg, Decl. = 26.24 \n(+1.51, -1.77) deg 90% PSF containment. Three cataloged >100 MeV \ngamma-ray sources are located within the 90% IC200921A localization \nerror (The Fourth Fermi-LAT catalog; The Fermi-LAT collaboration 2020, \nApJS, 247, 33). These are 4FGL J1303.0+2434 (associated with the BL Lac \nobject MG2 J130304+2434),�4FGL J1256.9+2736�(associated with the AGN \n �NGC 4839) and�4FGL J1310.6+2449�(associated with the BL Lac object \nCRATES J131038.52+244822.1). Based on a preliminary analysis of LAT data \nat timescales of 1-month and 1-day prior to T0, these objects are not \nsignificantly detected (>5sigma).\n\nWe searched for the existence of intermediate (days to years) timescale \nemission from a new gamma-ray transient source. Preliminary analysis \nindicates no significant (>5sigma) new excess emission (>100 MeV) at the \nIC200921A best-fit position. Assuming a power-law spectrum (photon index \n= 2.0 fixed) for a point source at the IceCube best-fit position, the \n >100 MeV flux upper limit (95% confidence) is < 2.8e-10 ph cm^-2 s^-1 \nfor ~12-years (2008-08-04 / 2020-09-21 UTC), < 3.7e-9 (< 6.1e-8) ph \ncm^-2 s^-1 for a 1-month (1-day) integration time before T0.\n\nIn the analysis of the ~12-years integrated LAT data (0.1 - 800 GeV), a \n4.7 sigma new excess of gamma rays, Fermi J1256.9+2630, was detected 1.0 \ndeg offset from the best-fit IC200921A position and within the 90% \nconfidence localization of the direction of the neutrino. Assuming a \npower-law spectrum, the best-fit localization is (J2000) RA:�194.23 deg, \nDec: 26.51 deg (7.4 arcmin 99% containment, 3.6 arcmin 68% containment). \nThe gamma-ray best-fit spectral parameters are flux = (4+/-3)e-10 ph \ncm^-2 s^-1 and index = 1.8+/-0.2. In a preliminary analysis of the LAT \ndata over 1-day and 1-month prior T0, Fermi J1256.9+2630�is not \nsignificantly detected in the LAT data. All values include \nthe�statistical uncertainty only.\n\nSince Fermi normally operates in an all-sky scanning mode, regular \nmonitoring of this source 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). The Fermi-LAT is a pair \nconversion telescope designed to cover the energy band from 20 MeV to \ngreater than 300 GeV. It is the product of an international \ncollaboration between NASA and DOE in the U.S. and many scientific \ninstitutions across France, Italy, Japan and Sweden.",
  "circularId": 28481,
  "createdOn": 1600847764000,
  "email": "simone.garrappa@desy.de",
  "subject": "Fermi-LAT Gamma-ray Observations of IceCube-200921A and detection of a new gamma-ray source, Fermi J1256.9+2630",
  "submitter": "Simone Garrappa at DESY  <simone.garrappa@desy.de>",
  "eventId": "IceCube-200921A"
}