Black hole masses from X-rays

TL;DR

This paper presents two X-ray based methods for estimating black hole masses, utilizing variability amplitude and photon index correlations, with demonstrated small intrinsic scatter and potential for broad application.

Contribution

It introduces and validates two novel X-ray only techniques for black hole mass estimation, improving accuracy and applicability.

Findings

X-ray variability amplitude correlates inversely with BH mass.

Photon index Gamma correlates with Eddington ratio and bolometric correction.

Both methods show small intrinsic scatter, indicating reliability.

Abstract

We discuss two methods to estimate black hole (BH) masses using X-ray data only: from the X-ray variability amplitude and from the photon index Gamma. The first method is based on the anti-correlation between BH mass and X-ray variability amplitude. Using a sample of AGN with BH masses from reverberation mapping, we show that this method shows small intrinsic scatter. The second method is based on the correlation between Gamma and both the Eddington ratio L_{bol}/L_{Edd} and the bolometric correction L_{bol}/L_{2-10keV}.