New version:
https://fermi.gsfc.nasa.gov/ssc/data/access/lat/8yr_catalog/

https://arxiv.org/abs/1902.10045

We distribute a preliminary version of the fourth Fermi Large Area
Telescope source catalog (4FGL) meant to help in writing 2019 NASA
Fermi Guest Investigator proposals. This supersedes the FL8Y source
list distributed in 2018. Based on the first eight years of science
data from the Fermi Gamma-ray Space Telescope mission and the 50 MeV -
1 TeV range, it is the deepest yet in this energy range. Relative to
the 3FGL catalog, the 4FGL catalog has twice as much exposure as well
as a number of analysis improvements, including an updated model for
Galactic diffuse gamma-ray emission. The 4FGL catalog includes 5098
sources above 4 sigma significance, for which we provide localization
and spectral properties. Seventy-five sources are modeled explicitly as
spatially extended, and overall 364 sources are considered as identified
based on angular extent or correlated variability observed at other
wavelengths. For 1525 sources we have not found plausible counterparts
at other wavelengths. More than 2940 of the identified or associated
sources are active galaxies of the blazar class, 241 are pulsars.


The Large Area Telescope (LAT) on board NASA's Fermi Gamma-ray Space
Telescope (launched June 11, 2008) surveys the entire sky each day. This
web page presents the fourth full catalog of LAT sources, based on 8
years of survey data and the 50 MeV-1 TeV range. For a full explanation
about the catalog and its construction see the Fermi-LAT Fourth Source
Catalog Paper (4FGL) available on arxiv.

The source designation is 4FGL JHHMM.m+DDMM(c,e,i,s) where the 4 refers
to the fourth catalog (1FGL was released at 1 year, 2FGL at 2 years, and
3FGL at 4 years) and FGL represents Fermi Gamma-ray LAT. The optional "e",
"i" and "s" designators are explained in the caveats below.


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#  arXiv/1501.02003v1.pdf # Fermi Large Area Telescope Third Source
Catalog # F. Acero+ 2015

Abstract

We present the third Fermi Large Area Telescope source catalog (3FGL)
of sources in the 100 MeV-300 GeV range. Based on the first four years of
science data from the Fermi Gamma-ray Space Telescope mission, it is the
deepest yet in this energy range. Relative to the 2FGL catalog, the 3FGL
catalog incorporates twice as much data as well as a number of analysis
improvements, including improved calibrations at the event reconstruction
level, an updated model for Galactic diffuse gamma emission, a refined
procedure for source detection, and improved methods for associating LAT
sources with potential counterparts at other wavelengths. The 3FGL catalog
includes 3033 sources above 4-sigma significance, with source location
regions, spectral properties, and monthly light curves for each. Of
these, 78 are flagged as potentially being due to imperfections in the
model for Galactic diffuse emission. Twenty-five sources are modeled
explicitly as spatially extended, and overall 232 sources are considered
as identified based on angular extent or correlated variability (periodic
or otherwise) observed at other wavelengths. For 1009 sources we have not
found plausible counterparts at other wavelengths. More than 1100 of the
identified or associated sources are active galaxies of the blazar class;
several other classes of non-blazar active galaxies are also represented
in the 3FGL. Pulsars represent the largest Galactic source class. From
source counts of Galactic sources we estimate the contribution of
unresolved sources to the Galactic diffuse emission is 3% at 1 GeV.