{
  "bibcode": "2022GCN.31653....1G",
  "body": "S. Garrappa (DESY-Zeuthen), S. Buson (Univ. of Wuerzburg), C. C. Cheung \n(Naval Research Laboratory) and J. Sinapius (DESY-Zeuthen) on behalf of \nthe Fermi-LAT collaboration:\n\nWe report an analysis of observations of the vicinity of the high-energy \nneutrino event IC220225A (GCN 31650) 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 2022-02-25 14:12:00.7 UTC \n(T0) with J2000 position RA = 34.7 (+3.1, -2.6) deg, Dec = 0.0 (+1.8, \n-1.5) deg (90% PSF containment).\n\nTwo cataloged >100 MeV gamma-ray sources are located within the 90% \nIC220225A localization error (The Fourth Fermi-LAT catalog, 4FGL-DR3; \nThe Fermi-LAT collaboration 2022, arXiv:2201.11184). These are 4FGL \nJ0217.8+0144, located ~1.75 deg from the neutrino best-fit position and \nassociated with the flat-spectrum radio quasar PKS 0215+015 located at z \n= 1.715 (Foltz & Chaffee 1987, AJ, 93, 529) and 4FGL J0208.5-0046, \nlocated ~2.7 deg from the neutrino best-fit position and associated with \nthe BL Lac object PKS 0205-010 with an uncertain SDSS-based redshift \n(Richards et al. 2004, ApJS, 155, 258; Richards et al. 2009, ApJS, 180, \n67). Based on a preliminary analysis of the LAT data over a 1-day and \n1-month integration time before T0, 4FGL J0208.5-0046 is not \nsignificantly detected at gamma rays.\n\n4FGL J0217.8+0144 has been in an enhanced gamma-ray activity state since \nmid-2021.�� Preliminary analysis of the 1-day interval preceding T0 \nindicates that the source is in a high state with flux (E>100 MeV) of \n(3+/-1) x 10^-7 photons cm^-2 s^-1 (integrated before T0, statistical \nuncertainty only) and power-law index 2.3 +/- 0.3. This flux is more \nthan 7 times greater than the average flux reported in the 4FGL-DR3 \ncatalog. Averaged over the month preceding T0, the flux (E>100 MeV) is \n(1.6+/-0.2) x 10^-7 photons cm^-2 s^-1 (statistical uncertainty only), \nmore than 3 times greater than the average flux reported in the 4FGL-DR3 \ncatalog, and the power-law index is 2.1 +/- 0.1 . The gamma-ray spectral \nindices of the flaring state are consistent with the value reported in \nthe latest 4FGL-DR3 catalog (index = 2.21 +/- 0.02). A preliminary light \ncurve can be accessed via the Fermi-LAT Light-Curve Repository at \nhttps://fermi.gsfc.nasa.gov/ssc/data/access/lat/LightCurveRepository/source.php?source_name=4FGL_J0217.8+0144.\n\nWe searched for the existence of intermediate (months to years) \ntimescale emission from a new gamma-ray transient source. Preliminary \nanalysis indicates no significant (>5sigma) new excess emission (> 100 \nMeV) at the the IC220225A best-fit position. Assuming a power-law \nspectrum (photon index = 2.0 fixed) for a point source at the IceCube \nbest-fit position, the >100 MeV flux upper limit (95% confidence) is < \n2.5 x 10^-10 ph cm^-2 s^-1 for ~13-years (2008-08-04 / 2022-02-25 UTC), \n< 1.0x 10^-8 (< 1.1 x 10^-7) ph cm^-2 s^-1 for a 1-month (1-day) \nintegration time before T0.\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). We encourage \nmultifrequency observations of these sources.\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": 31653,
  "createdOn": 1645839573000,
  "email": "simone.garrappa@desy.de",
  "subject": "Fermi-LAT Gamma-ray Observations of IceCube-220225A",
  "submitter": "Simone Garrappa at DESY  <simone.garrappa@desy.de>",
  "eventId": "IceCube-220225A"
}