A new cosmological distance measure using AGN X-ray variability

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We report the discovery of a luminosity distance estimator using Active Galactic Nuclei (AGN).

• We combine the correlation between the X-ray variability amplitude and the Black Hole (BH) mass with the single epoch spectra BH mass estimates which depend on the AGN luminosity and the line width emitted by the broad line region.
• We demonstrate that significant correlations do exist which allows one to predict the AGN (optical or X-ray) luminosity as a function of the AGN X-ray variability and either the HBeta or the PaBeta line widths.
• In the best case, when the PaBeta is used, the relationship has an intrinsic dispersion of ~0.6 dex.