GCN Circular 28884

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

We report an analysis of observations of the vicinity of the 
IceCube-HAWC coincidence alert (GCN�28865) with all-sky survey data from 
the Large Area Telescope (LAT), on board the Fermi Gamma-ray Space 
Telescope. The HAWC event was detected in a 6.42 hours interval from 
 �2020-11-07 at 09:29:47 UT and 2020-11-07 at 15:55:31 UT with J2000 
position RA = 140.20 �deg, Decl. = 29.76 deg �and a 90% PSF containment 
of 0.271 deg . No cataloged >100 MeV gamma-ray sources (The Fourth 
Fermi-LAT catalog; The Fermi-LAT collaboration 2020, ApJS, 247, 33)�are 
located within the 90% NuEm-201107A localization error.

We searched for short (hours to day) timescale emission from a new 
gamma-ray transient source. Preliminary analysis indicates no 
significant (> 5 sigma) new excess emission (> 100 MeV) at 
the�NuEm-201107A�best-fit position. Assuming a power-law spectrum 
(photon index = 2.0 fixed) for a point source at the 
NuEm-201107A�best-fit position, the >100 MeV flux upper limit (95% 
confidence) is < 1.5e-7 ph cm^-2 s^-1 for ~6.4 hours, < 5.5e-8 �ph cm^-2 
s^-1 for a 1-day integration time before 2020-11-07 at 15:55:31 UT.

Since Fermi normally operates in an all-sky scanning mode, regular 
monitoring of this source will continue. For these observations the 
Fermi-LAT contact persons are S. Garrappa (simone.garrappa at�desy.de) 
and S. Buson (sara.buson at�uni-wuerzburg.de). 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.