Third Catalog of Hard Fermi-LAT Sources (3FHL) FERMI3FHL ivo://nasa.heasarc/fermi3fhl NASA/GSFC HEASARC Ackermann et al. 2026-10-09 NASA/GSFC HEASARC help desk heasarc-vo at athena.gsfc.nasa.gov Survey Source This is a catalog of sources detected above 10 GeV by the Fermi-Large Area Telescope (LAT) in the first 7 years of data using the Pass 8 event-level analysis. It contains 1558 objects characterized in the 10 GeV to 2 TeV energy range. The sensitivity and angular resolution are improved by factors of 3 and 2 relative to the previous LAT catalog at the same energies (1FHL). The vast majority of detected sources (79%) are extragalactic, including 16 sources located at very high redshift (z > 2). Nine percent of the sources are Galactic and 12% are unassociated (or associated with a source of unknown nature). The high-latitude sky and the Galactic plane are observed with an average sensitivity of 0.5% and 1% of the Crab Nebula flux above 10 GeV, respectively. The catalog includes 225 new gamma-ray sources. The substantial increase in the number of photons (more than 4 times relative to the 1FHL and 10 times to the 2FHL) also allows us to characterize spectral curvature for 32 sources and flux variability for 163 of them. Furthermore, we estimate that for the same energy flux limit of 10<sup>-12</sup> erg cm<sup>2</sup> s<sup>-1</sup>, the energy range above 10 GeV has twice as many sources as the range above 50 GeV, which confirms and quantifies the importance of lowering the energy threshold of Cherenkov telescopes as much as possible in order to increase the number of available sources. This database table was first ingested by the HEASARC in December 2017 using electronic data obtained from the Fermi Science Support Center (FSSC). That data is available at <a href="http://fermi.gsfc.nasa.gov/ssc/data/access/lat/3FHL/">http://fermi.gsfc.nasa.gov/ssc/data/access/lat/3FHL/</a>. This is a service provided by NASA HEASARC . 2017ApJS..232...18A https://heasarc.gsfc.nasa.gov/W3Browse/all/fermi3fhl.html Catalog Research served-by HEASARC TAP https://heasarc.gsfc.nasa.gov/xamin/vo/cone?showoffsets&table=fermi3fhl& GET text/xml 180 99999 true 87.0374 -87.6309 0.333333333333333 https://heasarc.gsfc.nasa.gov/xamin/vo/tap https://heasarc.gsfc.nasa.gov/cgi-bin/W3Browse/getvotable.pl?name=fermi3fhl GET text/xml https://heasarc.gsfc.nasa.gov/cgi-bin/W3Browse/w3query.pl?tablehead=name=heasarc_fermi3fhl&Action=More+Options&Action=Parameter+Search&ConeAdd=1 FERMI 0.333333333333333 Gamma-ray public fermi3fhl Third Catalog of Hard Fermi-LAT Sources (3FHL) name The 3FHL Catalog Source Identifier (3FHL JHHMM.s+DDMM) 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 error_radius Position Uncertainty at 95% Confidence Level degree stat.error;pos double nullable flux The 10-1000 GeV Photon Flux photon/cm^2/s phot.flux;em.gamma.hard double nullable flux_error 1-Sigma Uncertainty in the 10-1000 GeV Photon Flux photon/cm^2/s stat.error;phot.flux;em.gamma.hard double nullable energy_flux Energy Flux from 10-1000 GeV from Power-Law Spectral Fit erg/s/cm^2 phot.flux;em.gamma.hard double nullable energy_flux_error 1-Sigma Uncertainty in the Energy Flux erg/s/cm^2 stat.error;phot.flux;em.gamma.hard double nullable source_class Class Designation for the Most Likely Association src.class char nullable assoc_name_1 Primary Name of Associated Source meta.id.assoc char nullable tev_assoc_flag TeV Association Flag, If Any meta.code char nullable flux_20_50_gev_pos_err Photon Flux from 20-50 GeV Positive Uncertainty photon/cm^2/s stat.error;phot.flux;em.gamma double nullable flux_0p5_2_tev_pos_err Photon Flux from 0.5-2 TeV Positive Uncertainty photon/cm^2/s stat.error;phot.flux;em.gamma double nullable beta_error 1-Sigma Uncertainty on Beta stat.error;spect.index double 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flux_50_150_gev_neg_err Photon Flux from 50-150 GeV Negative Uncertainty photon/cm^2/s stat.error;phot.flux;em.gamma double nullable redshift Redshift src.redshift double nullable nufnu_150_500_gev Spectral Energy Distribution from 150-500 GeV erg/cm^2/s phot.flux.density;em.gamma double nullable num_bayesian_blocks Number of Change Points in Bayesian Blocks Light Curve (1 for Non-Variable) stat.param;src.var;em.gamma.hard short nullable assoc_tevcat Designation of the Most Likely Associated Source in the TeVCat meta.id.assoc char nullable flux_150_500_gev_pos_err Photon Flux from 150-500 GeV Positive Uncertainty photon/cm^2/s stat.error;phot.flux;em.gamma double nullable nufnu_0p5_2_tev Spectral Energy Distribution from 0.5-2 TeV erg/cm^2/s phot.flux.density;em.gamma double nullable alt_gammaray_name Association with Other Catalogs of GeV Gamma-Ray Sources, If Any meta.id.assoc char nullable nufnu_50_150_gev Spectral Energy Distribution from 50-150 GeV erg/cm^2/s phot.flux.density;em.gamma double nullable flux_density Differential Flux At Pivot Energy photon/cm^2/GeV/s phot.flux.density double nullable sqrt_ts_20_50_gev Square Root of Test Statistic for the 20-50 MeV Flux stat.likelihood;phot.flux double nullable flux_10_20_gev_neg_err Photon Flux from 10-20 GeV Negative Uncertainty photon/cm^2/s stat.error;phot.flux;em.gamma double nullable sqrt_ts_0p5_2_tev Square Root of Test Statistic for the 0.5-2 TeV Flux stat.likelihood;phot.flux double nullable pivot_energy Energy At Which Error on Differential Flux Is Minimal GeV em.energy double nullable flux_density_error 1-Sigma Uncertainty in the Differential Flux at Pivot Energy photon/cm^2/GeV/s stat.error;phot.flux.density double nullable beta Curvature Parameter for LogParabola Type spect.index double nullable flux_0p5_2_tev_neg_err Photon Flux from 0.5-2 TeV Negative Uncertainty photon/cm^2/s stat.error;phot.flux;em.gamma double nullable assoc_name_2 Secondary Name of Associated Source meta.id.assoc char nullable assoc_prob_lr Probability of Association from the Likelihood Ratio Method stat.probability double nullable extended_source_name Cross-Reference to the Extension for Extended Sources, If Any meta.id.assoc char nullable flux_150_500_gev Photon Flux from 150-500 GeV from Power-Law Spectral Fit photon/cm^2/s phot.flux;em.gamma.hard double nullable bii Galactic Latitude degree pos.galactic.lat double nullable sqrt_ts_50_150_gev Square Root of Test Statistic for the 50-150 MeV Flux stat.likelihood;phot.flux double nullable spectral_index Spectral Index at the Pivot Energy When Fitting with LogParabola spect.index;em.gamma.hard double nullable flux_10_20_gev Photon Flux from 10-20 GeV from Power-Law Spectral Fit photon/cm^2/s phot.flux;em.gamma.hard double nullable powerlaw_index_error 1-Sigma Uncertainty in the PowerLaw Index stat.error;spect.index double nullable flux_50_150_gev_pos_err Photon Flux from 50-150 GeV Positive Uncertainty photon/cm^2/s stat.error;phot.flux;em.gamma double nullable flux_150_500_gev_neg_err Photon Flux from 150-500 GeV Negative Uncertainty photon/cm^2/s stat.error;phot.flux;em.gamma double nullable powerlaw_index Spectral Index When Fitting with PowerLaw spect.index double nullable spectrum_type Spectral Type (PowerLaw or LogParabola) spect char 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