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## FERMI3FHL - Third Catalog of Hard Fermi-LAT Sources (3FHL) |
HEASARC Archive |

**Name**

The source designation, 3FHL JHHMM.m+DDMM[e], constructed according to the
IAU Specifications for Nomenclature, in which the Right Ascension and
Declination have been truncated to 0.1 decimal minutes and 1', respectively.
The '3' refers to the second catalog and 'FHL' represents "Fermi Hard LAT". A
name ending with 'e' indicates an extended source.

**RA**

The Right Ascension of the gamma-ray source in the selected equinox.

**Dec**

The Declination of the gamma-ray source in the selected equinox.

**LII**

The Galactic Longitude of the gamma-ray source in decimal degrees.

**BII**

The Galactic Latitude of the gamma-ray source in decimal degrees.

**Error_Radius**

The position uncertainty at 95% confidence level in decimal degrees.

**Roi**

The region of interest number.

**Significance**

The gamma-ray source significance, in units of sigma.

**Pivot_Energy**

The energy at which the error on differential photon flux is minimal
(decorrelation energy for the power-law fit). Derived from the likelihood
analysis over the full band.

**Flux_Density**

The differential photon flux at the pivot energy. Derived from the likelihood
analysis over the full band.

**Flux_Density_Error**

The 1-sigma error on differential photon flux at the pivot energy.

**Flux**

The integral photon flux between 10 GeV and 1 TeV, in photon/cm^{2}/s.

**Flux_Error**

The 1-sigma uncertainty on integral photon flux between 10 GeV and 1 TeV, in
photon/cm^{2}/s.

**Energy_Flux**

The energy flux from 10 GeV to 1 TeV, in erg/cm^{2}/s.

**Energy_Flux_Error**

The 1-sigma uncertainty on energy flux from 10 GeV to 1 TeV, in erg/cm^{2}/s.

**Curve_Significance**

The significance (in sigma units) of the fit improvement between PowerLaw and
LogParabola. A value greater than 9 triggers switching to the curved spectrum.

**Spectrum_Type**

The spectral type (PowerLaw or LogParabola).

**Spectral_Index**

The spectral index at the pivot energy when fitting with the LogParabola model.

**Spectral_Index_Error**

The 1-sigma uncertainty on the spectral index.

**Beta**

The curvature parameter when fitting with the LogParabola model.

**Beta_Error**

The 1-sigma error on beta.

**Powerlaw_Index**

The spectral index when fitting with the power law model.

**Powerlaw_Index_Error**

The 1-sigma error on the power-law index.

**Flux_10_20_GeV**

The integral photon flux from 10 GeV to 20 GeV, in photon/cm^{2}/s.

**Flux_10_20_GeV_Neg_Err**

The lower (negative) uncertainty on integral photon flux from 10 GeV to 20
GeV, in photon/cm^{2}/s.

**Flux_10_20_GeV_Pos_Err**

The upper (positive) uncertainty on integral photon flux from 10 GeV to 20
GeV, in photon/cm^{2}/s.

**nuFnu_10_20_GeV**

The spectral energy distribution from 10 GeV to 20 GeV, in erg/cm^{2}/s.

**Sqrt_TS_10_20_GeV**

The square root of the test statistic between 10 GeV and 20 GeV.

**Flux_20_50_GeV**

The integral photon flux from 20 GeV to 50 GeV, in photon/cm^{2}/s.

**Flux_20_50_GeV_Neg_Err**

The lower (negative) uncertainty on integral photon flux from 20 GeV to 50
GeV, in photon/cm^{2}/s.

**Flux_20_50_GeV_Pos_Err**

The upper (positive) uncertainty on integral photon flux from 20 GeV to 50
GeV, in photon/cm^{2}/s.

**nuFnu_20_50_GeV**

The spectral energy distribution from 20 GeV to 50 GeV, in erg/cm^{2}/s.

**Sqrt_TS_20_50_GeV**

The square root of the test statistic between 20 GeV and 50 GeV.

**Flux_50_150_GeV**

The integral photon flux from 50 GeV to 150 GeV, in photon/cm^{2}/s.

**Flux_50_150_GeV_Neg_Err**

The lower (negative) uncertainty on integral photon flux from 50 GeV to 150
GeV, in photon/cm^{2}/s.

**Flux_50_150_GeV_Pos_Err**

The upper (positive) uncertainty on integral photon flux from 50 GeV to 150
GeV, in photon/cm^{2}/s.

**nuFnu_50_150_GeV**

The spectral energy distribution from 50 GeV to 150 GeV, in erg/cm^{2}/s.

**Sqrt_TS_50_150_GeV**

The square root of the test statistic between 50 GeV and 150 GeV.

**Flux_150_500_GeV**

The integral photon flux from 150 GeV to 500 GeV, in photon/cm^{2}/s.

**Flux_150_500_GeV_Neg_Err**

The lower (negative) uncertainty on integral photon flux from 150 GeV to 500
GeV, in photon/cm^{2}/s.

**Flux_150_500_GeV_Pos_Err**

The upper (positive) uncertainty on integral photon flux from 150 GeV to 500
GeV, in photon/cm^{2}/s.

**nuFnu_150_500_GeV**

The spectral energy distribution from 150 GeV to 500 GeV, in erg/cm^{2}/s.

**Sqrt_TS_150_500_GeV**

The square root of the test statistic between 150 GeV and 500 GeV.

**Flux_0p5_2_Tev**

The integral photon flux from 0.5 TeV to 2 TeV, in photon/cm^{2}/s.

**Flux_0p5_2_Tev_Neg_Err**

The lower (negative) uncertainty in the integral photon flux from 0.5 TeV to
2 TeV, in photon/cm^{2}/s.

**Flux_0p5_2_Tev_Pos_Err**

The upper (positive) uncertainty in the integral photon flux from 0.5 TeV to
2 TeV, in photon/cm^{2}/s.

**nuFnu_0p5_2_Tev**

The spectral energy distribution from 0.5 TeV to 2 TeV, in erg/cm^{2}/s.

**Sqrt_TS_0p5_2_Tev**

The square root of the test statistic between 0.5 TeV to 2 TeV.

**Npred**

The predicted number of photons from the model.

**HEP_Energy**

The highest energy among photons probably coming from the source, in GeV.

**HEP_Prob**

The probability that the highest energy photon is coming from the source.

**Num_Bayesian_Blocks**

The number of Bayesian blocks from variability analysis, where 1 means that the
source was non-variable and -1 means the source could not be tested.

**Extended_Source_Name**

The cross reference to the extended source table, if any.

**Alt_GammaRay_Name**

The name of the association of the 3FHL source with a source in another
catalog of GeV gamma-ray sources, if any.

**Tev_Assoc_Flag**

This parameter can contain a flag indicating a possible association with a
TeV source, coded as follows:

P = positional association with non-extended source in TeVCat; E = associated with an extended source in TeVCat; N = no TeV association

**Assoc_TeVCat**

The name of the most likely associated source in the TeVCat.

**Source_Class**

The astrophysical class of the counterpart of the gamma-ray source, using the
schema given below, where upper-case letters are used to indicate
'identified' counterparts whereas lower-case letters indicate 'associated'
counterparts.

agn = Non-blazar active galaxy bcu = Blazar candidate of uncertain type bin = Binary bll = BL Lac type of blazar fsrq = Flat spectrum radio quasar type of blazar glc = Globular cluster hmb = High-mass binary nlsy1 = Narrow-line Seyfert 1 psr = Pulsar pwn = Pulsar Wind Nebula rdg = Radio galaxy sbg = Starburst galaxy sfr = Star-forming region snr = Supernova remnant spp = Unclear whether SNR or PWN

**Assoc_Name_1**

The name of identified or likely associated source.

**Assoc_Name_2**

The alternate name of identified or likely associated source.

**Assoc_Prob_Bay**

The probability of association according to the Bayesian method.

**Assoc_Prob_LR**

The probability of association according to the Likelihood Ratio method.

**Redshift**

The redshift of counterpart (negative means uncertain).

**Nupeak_Obs**

The observed synchrotron peak frequency, in Hz.