[vsnet-grb-info 23728] Fermi-LAT Gamma-ray Observations of IceCube-190922A

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  25827
SUBJECT: Fermi-LAT Gamma-ray Observations of IceCube-190922A 
DATE:    19/09/23 22:35:07 GMT
FROM:    Sara Buson at GSFC/Fermi  <sara.buson at gmail.com>

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 IC190922A neutrino event (GCN 25802) 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 09:42:45.62 UT (T0) with J2000 position RA = 167.43 (+3.40, -2.63) deg, Decl. = -22.39 (+2.88, -2.89) deg 90% PSF containment. 
Three cataloged >100 MeV gamma-ray sources are located within the 90% IC190922A localization error. These are the BL Lac object 4FGL J1103.6-2329 (a.k.a. 1ES 1101-232), and the unassociated sources 4FGL J1120.0-2204 and 4FGL J1100.0-2044 (The Fermi-LAT collaboration, 2019, arXiv:1902.10045) at a distance of roughly 1.8 deg, 2.4 deg and 2.8 deg, respectively. Based on a preliminary analysis of the LAT data over the timescale of 1-day and 1-month before T0, these objects are 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 IC190922A 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 < 8.1e-10 ph cm^-2 s^-1 for ~11-years (2008-08-04 / 2019-09-22 UTC), < 4.6e-8 (< 1.4e-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 person are Simone Garrappa (simone.garrappa at desy.de <http://desy.de/>) and Sara Buson (sara.buson at gmail.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.