[vsnet-grb-info 23140] Fermi-LAT Gamma-ray Observations of IceCube-190730A

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  25239
SUBJECT: Fermi-LAT Gamma-ray Observations of IceCube-190730A
DATE:    19/07/31 22:13:43 GMT
FROM:    Simone Garrappa at DESY  <simone.garrappa at desy.de>

S. Garrappa (DESY-Zeuthen, DE), S. Buson (Univ. of Wuerzburg, DE; UMBC, 
USA) and D. Gasparrini (ASI SSDC; INFN Roma Tor Vergata, IT), on behalf 
of the Fermi-LAT collaboration:

We report an analysis of observations of the vicinity of the high-energy 
IC190730A neutrino event (GCN 25225) 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 2019-07-30 20:50:41.31 UTC 
(T0) with J2000 position RA = 225.79 (-1.43,+1.28) deg, Decl. = +10.47 
(-0.89,+1.14) deg 90% PSF containment. One cataloged >100 MeV gamma-ray 
source is located within the 90% IC190730A localization error, at a 
distance of roughly 0.3 deg. This is the object 4FGL J1504.4+1029 (The 
Fermi-LAT Collaboration 2019, arXiv:1902.10045) associated with the FSRQ 
PKS 1502+106. Based on a preliminary analysis of the LAT data over 
the-timescales of 1-day and 1-week prior to T0, this object is not 
significantly detected at gamma-rays. A preliminary light curve of the 
object is available at the FSSC 
(https://fermi.gsfc.nasa.gov/ssc/data/access/lat/msl_lc/source/PKS_1502p106). 
We note that for multiple years PKS1502+106 has been among the top-ten 
highest-fluence blazars in the whole sky when the integrated long-term 
GeV gamma-ray flux is considered. After a long high-activity phase of 
about 4.5 years, its gamma-ray flux has slowly decreased over the past 
year and is currently much lower than what was observed in the previous 
11 years of LAT monitoring.

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 IC190730A 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 < 1.9e-9 ph cm^-2 s^-1 for ~11-years (2008-08-04 / 
2019-07-31 UTC), < 4.6e-9 (< 1.4e-8) ph cm^-2 s^-1 for a 1-month 
(1-week) 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 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.