TITLE:   GCN CIRCULAR
NUMBER:  23339
SUBJECT: Fermi-LAT Gamma-ray Observations of IceCube-181014A
DATE:    18/10/15 00:42:07 GMT
FROM:    Sara Buson at GSFC/Fermi  <sara.buson@gmail.com>

T. Venters (tonia.m.venters at nasa.gov), S. Garrappa (DESY-Zeuthen), S. Buson (Univ. of Wuerzburg) on behalf of the Fermi-LAT collaboration:

We report an analysis of observations of the vicinity of the very high-energy IC181014A neutrino event (GCN 23338) 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 2018-10-14 11:52:46 UTC (T0) with J2000 position RA = 225.15 (-2.85,+1.40) deg, Decl. = -34.80 (-1.85,+1.15) deg 90% PSF containment. Two cataloged >100 MeV gamma-ray sources are located within the 90% IC181014A localization error. These are 3FGL J1457.4-3539 at a distance of roughly 1deg and associated with the flat-spectrum-radio-quasar PKS 1454-354, and 3FGL J1505.0-3432 at a distance of roughly 0.9deg and associated with the BL Lac object PMN J1505-3432 (Ackermann et al. 2015 ApJS 810, 14). Based on a preliminary analysis of the LAT data over the past month, neither of these two objects is detected in a high gamma-ray state.
 
We searched for the existence of intermediate (months to years) timescale emission from a new gamma-ray transient source. Preliminary analysis indicates no significant (>5sigma) new excess emission (0.1 - 300 GeV) within the IC181014A 90% confidence localization. Assuming a power-law spectrum (photon index = 2.2 fixed) for a point source at the IceCube best-fit position, the >100 MeV flux upper limit (95% confidence) is < 4.5e-8 (< 2.74e-8)  ph cm^-2 s^-1 for a 1-month (7-month) integration time before T0.
 
Since Fermi normally operates in an all-sky scanning mode, regular monitoring of this source will continue. For this source the Fermi-LAT contact persons are T. Venters (tonia.m.venters at nasa.gov), S. Garrappa (simone.garrappa at desy.de) and S. Buson (e-mail: sara.buson at gmail.com).
 
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.