{
  "bibcode": "2020GCN.28751....1B",
  "body": "S. Buson (Univ. of Wuerzburg), S. Garrappa (DESY-Zeuthen), C. C. Cheung \n(Naval Research Laboratory) and M. Ajello (Clemson Univ.) on behalf of \nthe Fermi-LAT collaboration:\n\nWe report an analysis of observations of the vicinity of the high-energy \nIC201021A neutrino event (GCN�28715) 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 2020-10-21 at \n06:37:47.48�UT (T0) with J2000 position RA = 260.82 (+1.73, -1.68) deg, \nDecl. = 14.55 (+1.35, -0.74) deg (90% PSF containment). No cataloged \n >100 MeV gamma-ray sources (The Fourth Fermi-LAT catalog, 4FGL; The \nFermi-LAT collaboration 2020, ApJS, 247, 33)�are located within the 90% \nIC201021A localization error.\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 \nIC201021A�best-fit position. Assuming a power-law spectrum (photon index \n= 2.0 fixed) for a point source at the IC201021A�best-fit position, the \n >100 MeV flux upper limit (95% confidence) is < 4.2e-10 ph cm^-2 s^-1 \nfor ~12-years (2008-08-04 to 2020-10-21 UTC), and < 1.3e-8 (< 4.3e-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, 10�arcmin offset \nfrom the best-fit IC201021A position, an excess of gamma rays, Fermi \nJ1725.5+1312, was detected in an analysis of the integrated LAT data \n(0.1 - 300 GeV) between 2008-08-04 and 2020-10-21. This putative new \nsource is detected at a statistical significance >3 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= 260.76 deg, Decl. = 14.39 deg (5�arcmin 68% containment, 11�arcmin 99% \ncontainment) with best-fit spectral parameters, flux = (1.8 +/- 0.5)e-9 \nph cm^-2 s^-1, index = 2.2 +/- 0.2.�In a preliminary analysis of the LAT \ndata over one day and one month prior T0, Fermi J1725.5+1312 is not \nsignificantly detected in the LAT data. All values include the \nstatistical uncertainty only.�The highest-energy photon likely \nassociated to the source is a ~52 GeV event (90% prob), detected on 2009 \nNovember 20.\n\nA possible counterpart of Fermi J1725.5+1312 is 1RXS J172314.4+142103 \n(RA = 260.812500 deg, Decl. = 14.350556 deg; Voges et al. 1999, A&A, \n349, 389) of unknown redshift. It is located 4�arcmin�from the Fermi \nJ1725.5+1312 best-fit position, and within the gamma-ray 68% positional \nuncertainty. This X-ray source has been previously reported by \nXMM-Newton, as XMMSL1 J172315.0+142102 (observed on 2006-09-04; Saxton \net al. 2008 A&A, 480, 611). A Swift follow up observation of the field \nof IC201021A was performed on 2020-10-21 and detected 1RXS \nJ172314.4+142103 at a flux consistent with catalogued values (GCN \n28724). A possible infrared�counterpart of 1RXS J172314.4+142103 is \nWISEA J172314.13+142101.5 (Cutri et al.�2013 wise.rept, 1). Coincident \nwith this WISE source there is�a faint radio source (~1.1 mJy peak at 3 \nGHz), as seen in the�the NRAO VLASS quick-look \nimage�(https://science.nrao.edu/vlass/data-access/vlass-epoch-1-quick-look-users-guide) \nfrom data obtained on 2019-03-30.\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 \n<http://desy.de/>) and S. Buson (sara.buson at uni-wuerzburg.de \n<http://uni-wuerzburg.de/>). The Fermi-LAT is a pair conversion \ntelescope designed to cover the energy band from 20 MeV to greater than \n300 GeV. It is the product of an international collaboration between \nNASA and DOE in the U.S. and many scientific institutions across France, \nItaly, Japan and Sweden.",
  "circularId": 28751,
  "createdOn": 1603394048000,
  "email": "simone.garrappa@desy.de",
  "subject": "Fermi-LAT Gamma-ray Observations of IceCube-201021A and detection of a new gamma-ray source, Fermi J1725.5+1312",
  "submitter": "Simone Garrappa at DESY  <simone.garrappa@desy.de>",
  "eventId": "IceCube-201021A"
}