Fermi LAT Gamma-ray Observations of IceCube-160731
ATel #9303; C. C. Cheung (NRL), M. W. Toomey (Penn State), D. Kocevski (NASA/GSFC), S. Buson (NASA/GSFC), on behalf of the Fermi-LAT collaboration
on 2 Aug 2016; 22:13 UT
Credential Certification: Teddy Cheung (ccheung@milkyway.gsfc.nasa.gov)
Subjects: Gamma Ray, >GeV, Neutrinos
We report follow-up of the extremely high-energy (EHE) IceCube-160731 neutrino event (AMON GCN notice; http://gcn.gsfc.nasa.gov/notices_amon/6888376_128290.amon ) 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 July 31 at 01:55:04 UTC with J2000 position, RA = 214.54 deg, Decl. = -0.33 deg. Follow up observations from other observatories have been reported (ATEL #9294, #9295, #9298, #9301, GCN #19743, #19752).
Preliminary analysis indicates no significant gamma-ray emission. 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 <1 x 10^-7 ph cm^-2 s^-1 in 2.25 days of exposure (beginning on 2016 July 31 at 00:00 UTC) and <0.6 x 10^-7 ph cm^-2 s^-1 in 8.25 days of exposure (beginning 2016 July 25 at 00:00 UTC). The latter time interval covers the period observed with AGILE (ATEL #9295).
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 persons are C.C. Cheung (Teddy.Cheung at nrl.navy.mil) and 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.
