FERMILAC ivo://nasa.heasarc/fermilac NASA/GSFC HEASARC Ajello et al. (Fermi LAT Collaboration) 2026-07-24 NASA/GSFC HEASARC help desk heasarc-vo at athena.gsfc.nasa.gov AGN This is the third update to the fourth catalog of active galactic nuclei (AGNs) detected by the Fermi Large Area Telescope (LAT). This version (4LAC-DR3) derives from the third data release of the 4FGL catalog based on 12 years of gamma-ray data with energies greater than 50 MeV. The spectral parameters, spectral energy distributions (SEDs), yearly light curves, and associations have been updated for all sources. The catalog contains includes 3407 AGN located at high Galactic latitudes (|b| > 10 degrees). This database table was first ingested by the HEASARC in February 2010. It was last updated (to the 4LAC-DR3 version) in June 2023 using electronic data obtained from the Fermi Science Support Center (FSSC). That data is available at <a href="https://fermi.gsfc.nasa.gov/ssc/data/access/lat/4LACDR3/">https://fermi.gsfc.nasa.gov/ssc/data/access/lat/4LACDR3/</a>. Note that this table does not contain the low-latitude sources given in a separate file there, which are not formally a part of the catalog. This is a service provided by NASA HEASARC . 2022ApJS..263...24A https://heasarc.gsfc.nasa.gov/W3Browse/all/fermilac.html Catalog Research served-by HEASARC TAP https://heasarc.gsfc.nasa.gov/xamin/vo/cone?showoffsets&table=fermilac& GET text/xml 180 99999 true 317.4619 -86.3078 0.166666666666667 https://heasarc.gsfc.nasa.gov/xamin/vo/tap https://heasarc.gsfc.nasa.gov/cgi-bin/W3Browse/getvotable.pl?name=fermilac GET text/xml https://heasarc.gsfc.nasa.gov/cgi-bin/W3Browse/w3query.pl?tablehead=name=heasarc_fermilac&Action=More+Options&Action=Parameter+Search&ConeAdd=1 FERMI 0.166666666666667 Gamma-ray public fermilac Fermi LAT Fourth AGN Catalog name Catalog Source Designation meta.id;meta.main char nullable ra Right Ascension degree pos.eq.ra;meta.main double nullable dec Declination degree pos.eq.dec;meta.main double nullable flux_1_100_gev Integral Photon Flux 1 to 100 GeV photon/cm^2/s phot.flux;em.gamma double nullable flux_1_100_gev_error 1-Sigma Uncertainty in Photon Flux 1 to 100 GeV photon/cm^2/s stat.error;phot.flux;em.gamma double nullable detection_significance Source Detection Significance (in Sigma Units) in the 50 MeV to 1 TeV Band sigma stat.fit.goodness;instr.background double nullable spectrum_type Spectral Type (PowerLaw, LogParabola, PLSuperExpCutoff) meta.code;spect char nullable assoc_name Name of Identified or Likely Associated Source meta.id.assoc char nullable analysis_flags Flags Indicate Possible Issues in Detection or Characterization of Source meta.code.qual short nullable "__x_ra_dec" System unit vector column double nullable "__y_ra_dec" System unit vector column double nullable "__z_ra_dec" System unit vector column double nullable "__row" System index column char nullable nufnu_syn Spectral Energy Distribution at the Synchrotron Peak Frequency erg/cm^2/s phot.flux.density;em.gamma double nullable pl_index_error 1-Sigma Uncertainty on Photon Index for PowerLaw Fit stat.error;spect.index double nullable lp_beta Curvature Parameter for LogParabola Fit spect.index double nullable bii Galactic Latitude degree pos.galactic.lat double nullable lii Galactic Longitude degree pos.galactic.lon double nullable energy_flux_error 1-Sigma Error in Energy Flux from 100 MeV to 100 GeV erg/cm^2/s stat.error;phot.flux double nullable pl_index Photon Index for PowerLaw Fit spect.index double nullable frac_variability_error 1-Sigma Uncertainty on Fractional Variability stat.error;src.var double nullable he_nufnu_peak_error 1-Sigma Uncertainty on Spectral Energy Distribution at Peak Energy erg/cm^2/s stat.error;phot.flux.density;em.gamma double nullable he_peak SED Peak Energy MeV em.energy double nullable lp_index_error 1-Sigma Uncertainty on Photon Index at Pivot Energy for LogParabola Fit stat.error;spect.index double nullable assoc_error_radius Position Uncertainty at 68% Confidence Level for Assoc_Name Counterpart degree stat.error;pos double nullable source_type Class Designation for Associated Source src.class char nullable sed_class Spectral Energy Distribution Classification Based on Synchrotron Peak Frequency src.class char nullable vlbi_assoc_name Designation of the VLBI Counterpart meta.id.assoc char nullable assoc_catalog Counterpart Catalog meta.id.assoc char nullable frac_variability Fractional Variability Computed from the Fluxes in Each Year src.var double nullable assoc_ra Right Ascension of Assoc_Name Counterpart degree pos.eq.ra double nullable lp_beta_error 1-Sigma Uncertainty on Curvature Parameter for LogParabola Fit stat.error;spect.index double nullable lp_index Photon Index at Pivot Energy for LogParabola Fit spect.index double nullable assoc_prob_bay Probability of Association from the Bayesian Method stat.probability double nullable assoc_dec Declination of Assoc_Name Counterpart degree pos.eq.dec double nullable energy_flux Energy Flux from 100 MeV to 100 GeV erg/cm^2/s phot.flux;em.gamma double nullable he_peak_error 1-Sigma Uncertainty on Peak Energy MeV stat.error;em.energy double nullable redshift Redshift src.redshift double nullable pivot_energy Energy at Which Error on Differential Flux Is Minimal MeV em.energy double nullable highest_energy_photon Highest Energy of the Photons from the Source GeV em.energy double nullable variability_index Measure of the Source Variability src.var.index double nullable he_nufnu_peak Spectral Energy Distribution at Peak Energy erg/cm^2/s phot.flux.density;em.gamma double nullable data_release Data Release Version meta.version short nullable assoc_prob_lr Probability of Association from the Likelihood Ratio Method stat.probability double nullable nu_syn Observed Synchrotron Peak Frequency Hz em.freq double nullable