TITLE:   GCN CIRCULAR
NUMBER:  25420
SUBJECT: Fermi-LAT Gamma-ray Observations of IceCube-190819A
DATE:    19/08/20 23:36:43 GMT
FROM:    Simone Garrappa at DESY  <simone.garrappa@desy.de>

S. Garrappa (DESY-Zeuthen), S. Buson (Univ. of Wuerzburg; UMBC) and R. 
Angioni (MPIfR-Bonn) on behalf of the Fermi-LAT collaboration:

We report an analysis of observations of the vicinity of the high-energy 
IC190819A neutrino event (GCN 25402) 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 2019-08-19 17:34:24.24 UTC 
(T0) with J2000 position RA = 148.80 (-3.24,+2.07) deg, Decl. = 1.38 
(-0.75,+1.00) deg 90% PSF containment. One cataloged >100 MeV gamma-ray 
source is located within the 90% IC190819A localization error, at a 
distance of roughly 2.25 deg. This is the object 4FGL J0946.2+0104 (The 
Fermi-LAT Collaboration 2019, arXiv:1902.10045) associated with the BL 
Lac object 1RXS J094620.5+010459. 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 IC190819A 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 < 4.0e-10 ph cm^-2 s^-1 for ~11-years (2008-08-04 / 
2019-08-19 UTC), < 6.8e-8 (< 4.1e-9) 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 at desy.de) and S. Buson 
(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.