Hot Corona Properties of Swift/BAT detected AGN

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 Å. Virial supermassive black hole masses (SMBH, \mbh) are calculated from the $\mathrm{H}\beta$ line width and the corresponding broad line region size-luminosity empirical relation at 5100 Å. We find a strong anti-correlation between the fraction of energy released in corona ($F_x\equiv L_{14-195keV}/L_{\mathrm{Edd}}$) and the Eddington ratio ($\epsilon \equiv L_{\mathrm{Bol}}/L_{\mathrm{Edd}}$), $F_x\propto {\epsilon }^{-0.60\pm 0.1}$. It is found that this fraction also has a correlation with the SMBH mass, $F_x\propto {\epsilon }^{-0.74\pm 0.14}{M}_{\mathrm{BH}}^{-0.30\pm 0.03}$. 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, $\Gamma =2.17+0.21\log \epsilon$. However, this correlation is not robust because the relation is not statistically significant for its subsample of 32 RM AGNs with relatively reliable $M_{\mathrm{BH}}$ or its subsample of 166 AGNs with single-epoch $M_{\mathrm{BH}}$. We do not find a statistically significant relation between the photon index and the Eddington ratio taking into account an additional dependence on $F_x$.

Accepted for publication in MNRAS, 4 Figures, 1 Table

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Cited by in corpus (7)

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• Calibration of the virial factor $f$ in supermassive black hole masses of reverberation-mapped AGNs
• Magnetic-reconnection-heated corona in active galactic nuclei: refined disc-corona model and application to broad-band radiation
• An extended size-luminosity relation for the reverberation-mapped AGNs: the role of the accretion rate
• The supermassive black hole masses of reverberation-mapped active galactic nuclei
• The ${\sigma }_{\mathrm{H}\beta }$-based dimensionless accretion rate and its connection with the corona for AGN
• Source identification for the Swift-BAT 150-month hard X-ray catalog using soft X-ray observations