[vsnet-grb-info 23739] Fermi-LAT Gamma-ray Observations of IceCube-190922B

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  25838
SUBJECT: Fermi-LAT Gamma-ray Observations of IceCube-190922B
DATE:    19/09/24 07:50:37 GMT
FROM:    Simone Garrappa at DESY  <simone.garrappa at desy.de>

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

We report an analysis of observations of the vicinity of the high-energy 
IC190922B neutrino event (GCN 25806)  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  2019-09-22 at 23:03:55.56 
UT (T0) with J2000 position RA =  5.76 (+1.19, -1.37) deg, Decl. = -1.57 
(+0.93, -0.82) deg 90% PSF containment. No cataloged (>100 MeV) 
gamma-ray sources are found within the 90% IC190922B localization error.

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 IC190922B 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 < 1e-10 ph cm^-2 s^-1 for ~11-years (2008-08-04 / 
2019-09-23 UTC), < 1e-7 (< 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 this source will continue. For this source the Fermi-LAT 
contact persons are Simone Garrappa (simone.garrappa atdesy.de 
<http://desy.de/>) and Sara 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.