[vsnet-grb-info 24360] Fermi-LAT Gamma-ray Observations of IceCube-191215A

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  26459
SUBJECT: Fermi-LAT Gamma-ray Observations of IceCube-191215A
DATE:    19/12/16 23:47:09 GMT
FROM:    Simone Garrappa at DESY  <simone.garrappa at desy.de>

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 high-energy 
IC191215A neutrino event (GCN 26435) 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 2019-12-15 11:09:57.63 UTC 
(T0) with J2000 position RA =285.87 (+2.88 -3.19) deg, Decl. = 58.92 
(+1.85 -2.25) deg 90% PSF containment. One cataloged >100 MeV gamma-ray 
source is located within the 90% IC191215A localization error, at a 
distance of roughly 1.88 deg. This is the object 4FGL J1858.7+5708 (The 
Fermi-LAT Collaboration 2019, arXiv:1902.10045) associated with the 
blazar candidate object of uncertain type 87GB 185759.9+570427. Based on 
a preliminary analysis of the LAT data over the timescales of 1-day and 
1-month prior to T0, this object is not significantly detected at 
gamma-rays.

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 (> 100 
MeV) within the IC191215A 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 < 2.2e-10 ph cm^-2 s^-1 for ~11-years (2008-08-04 / 
2019-12-15 UTC), < 4.2e-8 (< 1e-8) ph cm^-2 s^-1 for a 1-day (1-month) 
integration time before T0.

Since Fermi normally operates in an all-sky scanning mode, regular 
monitoring of the region will continue. For this event the Fermi-LAT 
contact person 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.