# Hot Corona Properties of Swift/BAT detected AGN

## TL;DR

This study analyzes 208 AGNs detected in ultra-hard X-ray to explore hot corona properties, revealing correlations with black hole mass and accretion rate, and examining the photon index's relation to these parameters.

## Contribution

It provides new insights into the relationship between corona energy dissipation, black hole mass, and accretion rate in AGNs using a large, hard X-ray selected sample.

## Key findings

- Strong anti-correlation between corona energy fraction and Eddington ratio.
- Correlation between corona energy fraction, SMBH mass, and Eddington ratio.
- Weak correlation between X-ray photon index and Eddington ratio.

## Abstract

Using a sample of 208 broad-line active galactic nuclei (AGNs) from Swift/BAT AGN Spectroscopic Survey in ultra-hard X-ray band ($14-195$ keV), the hot corona properties are investigated, i.e. the fraction of gravitational energy dissipated in the hot corona and the hard X-ray photon index. The bolometric luminosity, \lb, is calculated from host-corrected luminosity at 5100 \AA. Virial supermassive black hole masses (SMBH, \mbh) are calculated from the $\rm H\beta$ line width and the corresponding broad line region size-luminosity empirical relation at 5100 \AA. We find a strong anti-correlation between the fraction of energy released in corona ($F_x \equiv L_{14-195 keV}/L_{\rm Edd}$) and the Eddington ratio ($ \varepsilon \equiv L_{\rm Bol}/L_{\rm Edd}$), $F_x \propto \varepsilon^{-0.60\pm 0.1}$. It is found that this fraction also has a correlation with the SMBH mass, $F_x \propto \varepsilon^{-0.74\pm 0.14} M_{\rm BH}^{-0.30\pm 0.03}$. Assuming that magnetic buoyancy and feild reconnection lead to the formation of a hot corona, our result favours the shear stress tensor being a proportion of the gas pressure. For our entire sample, it is found that the hard X-ray photon index $\Gamma$ has a weak but significant correlation with the Eddington ratio, $ \Gamma=2.17+0.21\log \varepsilon$. However, this correlation is not robust because the relation is not statistically significant for its subsample of 32 RM AGNs with relatively reliable $M_{\rm BH}$ or its subsample of 166 AGNs with single-epoch $M_{\rm BH}$. We do not find a statistically significant relation between the photon index and the Eddington ratio taking into account an additional dependence on $F_x$.