[vsnet-grb-info 23833] Fermi-LAT Gamma-ray Observations of IceCube-191001A

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  25932
SUBJECT: Fermi-LAT Gamma-ray Observations of IceCube-191001A
DATE:    19/10/03 08:28:18 GMT
FROM:    Simone Garrappa at DESY  <simone.garrappa at desy.de>

S. Garrappa (DESY-Zeuthen) and S. Buson (Univ. of Wuerzburg) on behalf 
of the Fermi-LAT collaboration:

We report an analysis of observations of the vicinity of the high-energy 
IC191001A neutrino event (GCN 25913)  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 2019-10-01  20:09:18.17 UTC 
(T0) with J2000 position RA = 314.08 (+6.56, -2.26) deg, Decl. = 12.94 
(+1.50, -1.47) deg 90% PSF containment. Two cataloged gamma-ray sources 
(The Fermi-LAT collaboration, 2019, arXiv:1902.10045) are found within 
the 90% localization error of IC191001A. These are the millisecond 
pulsar 4FGL J2052.7+1218 (a.k.a. PSR J2052+1218) and the blazar 
candidate of uncertain type 4FGL J2115.2+1218 (a.k.a. NVSS 
J211522+121802), at a distance of 1.1 deg and 4.7 deg from the best 
fit, respectively.

We searched for the existence of intermediate (days to years) timescale 
emission from a new gamma-ray transient source. Preliminary analysis 
indicates no significant (>5sigma) new excess emission (> 100 MeV) 
within the IC191001A 90% confidence localization. Assuming a power-law 
spectrum (photon index = 2.0 fixed) for a point source at the IceCube 
best-fit position, the >100 MeV flux upper limit (95% confidence) is < 
3.7e-10 ph cm^-2 s^-1 for ~11-years (2008-08-04 / 2019-10-02 UTC), < 
2e-8 (< 2.9e-7) ph cm^-2 s^-1 for a 1-month (1-day) 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 S. Garrappa (simone.garrappa atdesy.de 
<http://desy.de/>) and S. Buson (sara.buson atgmail.com 
<http://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.