{
  "bibcode": "2021GCN.29965....1G",
  "body": "S. Garrappa (DESY-Zeuthen), S. Buson (Univ. of Wuerzburg) and C. C. \nCheung (Naval Research Laboratory) on behalf of the Fermi-LAT collaboration:\n\nWe report an analysis of observations of the vicinity of the high-energy \nIC210503A neutrino event (GCN 29951) 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 2021-05-03 at 22:19:32.96 \nUT (T0) with J2000 position RA = 143.53 (+7.71, -5.16) deg, Decl. = \n41.81 (+5.02, -5.68) deg (90% PSF containment). Seventeen cataloged \ngamma-ray (>100 MeV) sources are located within the 90% IC210503A \nlocalization region (4FGL-DR2, The Fermi-LAT collaboration 2020, ApJS, \n247, 33). Based on a preliminary analysis of the LAT data over the \ntimescale of 1-day prior to T0, none of these objects is significantly \ndetected (> 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 IC210503A \nbest-fit position.� Assuming a power-law spectrum (photon index = 2.0 \nfixed) for a point source at the IC210503A best-fit position, the >100 \nMeV flux upper limit (95% confidence) is < 1e-10 ph cm^-2 s^-1 for \n~12-years (2008-08-04 to 2021-05-03 UTC), and < 6.3e-9 (< 4.6e-8) ph \ncm^-2 s^-1 for a 1-month (1-day) integration time before T0.\n\nBased on a preliminary analysis, the cataloged object 4FGL J0920.9+4441 \nis significantly (> 5 sigma) detected in a 1-month integration time \nbefore T0. The source is associated with the FSRQ� S4 0917+44 \n(Pauliny-Toth et al. 1978, AJ, 83, 451) at redshift z = 2.18645 (Hewett \nand Wild 2010, MNRAS, 405, 2302) and is detected with flux (>100 MeV) = \n(1.8 +/- 0.8)e-08 ph cm^-2 s^-1 (30% of the 4FGL catalog value) and \npower-law index = 2.1 +/- 0.5, consistent with the 4FGL value of 2.35 \n+/- 0.01. The source has not shown enhanced activity within the last \nyear, and it is not significantly detected at a timescale of 1-day \nbefore T0.\n\nWithin the 90% confidence localization of the neutrino, 3.76 deg offset \nfrom the best-fit IC210503A position, a new excess of gamma rays, Fermi \nJ0931.9+3633, was detected in an analysis of the integrated LAT data \n(100 MeV - 1 TeV) between 2008-08-04 and 2021-05-03. This putative new \nsource is detected at a statistical significance >5 sigma (calculated \nfollowing the prescription adopted in the 4FGL). Assuming a power-law \nspectrum, the candidate gamma-ray source has best-fit localization of RA \n= 142.97 deg, Decl. = 36.55 deg (5 arcmin 68% containment radius, 9 \narcmin 99% containment radius) with best-fit spectral parameters, flux = \n(8.7 +/- 4.5)e-10 ph cm^-2 s^-1, index = 2.0 +/- 0.2. In a preliminary \nanalysis of the LAT data over 1-day and 1-month prior to T0, Fermi \nJ0931.9+3633 is not significantly detected in the LAT data. All values \ninclude the statistical uncertainty only.\n\nA possible counterpart of Fermi J0931.9+3633 is the BL Lac object SDSS \nJ093209.60+363002.6 at RA=143.035791 deg, Dec=36.503676 deg, and \nredshift 0.15376 +/- 0.00017 (Anderson et al. 2007 AJ, 133, 313). This \nsource is located about 4 arcmin from the Fermi J0931.9+3633 best-fit \nposition, and within the gamma-ray 68% positional uncertainty.\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).\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": 29965,
  "createdOn": 1620426224000,
  "email": "simone.garrappa@desy.de",
  "subject": "Fermi-LAT Gamma-ray Observations of IceCube-210503A and detection of a new gamma-ray source, Fermi J0931.9+3633",
  "submitter": "Simone Garrappa at DESY  <simone.garrappa@desy.de>",
  "eventId": "IceCube-210503A"
}