English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Tools annual

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Presents the access of premium content as premium feature

Premium Content

Global: Zendy Plus annual

Global: Zendy Free Plan

Observations show that the accretion flows in low-luminosity active galacticnuclei (LLAGNs) probably have a two-component structure with an inner ADAF andan outer truncated accretion disk. As shown by Taam et al. (2012), thetruncation radius as a function of mass accretion rate is strongly affected byincluding the magnetic field within the framework of disk evaporation model,i.e., an increase of the magnetic field results in a smaller truncation radiusof the accretion disk. In this work, we calculate the emergent spectrum of aninner ADAF + an outer truncated accretion disk around a supermassive black holebased on the prediction by Taam et al. (2012). It is found that an increase ofthe magnetic field from $\beta=0.8$ to $\beta=0.5$ (with magnetic pressure$p_{\rm m}=B^2/{8\pi}=(1-\beta)p_{\rm tot}$, $p_{\rm tot}=p_{\rm gas}+p_{\rmm}$) results in an increase of $\sim 8.7$ times of the luminosity from thetruncated accretion disk. We found that the equipartition of gas pressure tomagnetic pressure, i.e., $\beta=0.5$, failed to explain the observedanti-correlation between $L_{\rm 2-10 keV}/L_{\rm Edd}$ and the bolometriccorrection $\kappa_{\rm 2-10 keV}$ (with $\kappa_{\rm 2-10 keV} = L_{\rmbol}/L_{\rm 2-10 keV}$). The emergent spectra for larger value $\beta=0.8$ or$\beta=0.95$ can well explain the observed $L_{\rm 2-10 keV}/L_{\rmEdd}$-$\kappa_{\rm 2-10 keV}$ correlation. We argue that in the diskevaporation model, the electrons in the corona are assumed to be heated only bya transfer of energy from the ions to electrons via Coulomb collisions, whichis reasonable for the accretion with a lower mass accretion rate. Coulombheating is the dominated heating mechanism for the electrons only if themagnetic field is strongly sub-equipartition, which is roughly consistent withobservations.

The disk evaporation model for the spectral features of low-luminosity active galactic nuclei