TITLE: GCN CIRCULAR NUMBER: 20144 SUBJECT: Fermi LAT Gamma-ray Observations of IceCube-161103 DATE: 16/11/08 00:16:06 GMT FROM: Daniel Kocevski at GSFC D. Kocevski (NASA/MSFC), N. Omodei (Stanford University), M. Ohno (Hiroshima Univ.), and B. Carpenter (Catholic U.), on behalf of the Fermi-LAT collaboration. We report follow-up of the very high-energy IceCube-161103 neutrino event (GCN circular 20119) with all-sky survey data from the Large Area Telescope (LAT), on board the Fermi Gamma-ray Space Telescope. The IceCube event was detected on 2016-11-03 09:07:31.12 UTC (T0) with J2000 position, RA = 40.83 deg, Decl. = 12.56 deg. The position was outside the LAT field-of-view at the time of detection and remained so until roughly T0 + 5000s. Therefore, the LAT can place no constraints on the existence of a prompt gamma-ray transient coincident with the detection of the neutrino event. There are no cataloged gamma-ray sources consistent with the IceCube-161103 localization. The closest gamma-ray sources are 3FGL J0239.4+1326 and 3FGL J0242.3+1059 at distances of roughly 1.29 deg and 1.58 deg respectively. Neither show any significant variability in their monthly 3FGL light curves. We also search for the existence of intermediate (hours to days) timescale emission from a new gamma-ray transient source. Preliminary analysis indicates no significant excess gamma-ray emission coincident with the IceCube-161103 localization. Assuming a single power-law (photon index = 2.2 fixed) for a point source at the IceCube position, the >100 MeV flux upper limits (95% confidence) are < 2.5 x 10^-7 ph cm^-2 s^-1 in 1 day of exposure beginning 12 hours prior to the IceCube detection (2016-11-02 07:21:31 UTC) and < 3.1 x 10^-7 ph cm^-2 s^-1 in 12 hours of exposure beginning at the time the IceCube detection (2016-11-03 09:07:31.12 UTC). Longer timescale analysis will continue as data becomes available. Because Fermi operates in an all-sky scanning mode, regular gamma-ray monitoring of this source region will continue. For this source the Fermi LAT contact person is D. Kocevski (e-mail: daniel.kocevski at nasa.gov) The Fermi LAT is a pair conversion telescope designed to cover the energy band from 20 MeV to greater than 300 GeV. It is the product of an international collaboration between NASA and DOE in the U.S. and many scientific institutions across France, Italy, Japan and Sweden.