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 Plus annual

Presents the access of premium content as premium feature

Premium Content

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 annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

The geometry of the accretion flow around stellar mass and supermassive blackholes depends on the accretion rate. Broad iron emission lines originating fromthe irradiation of cool matter can indicate that there is an inner disk below ahot coronal flow.These emission lines have been detected in X-ray binaries.Observations with the Chandra X-ray Observatory, XMM Newton and Suzaku haveconfirmed the presence of these emission lines also in a large fraction ofSeyfert-1 active galactic nuclei (AGN). We investigate the accretion flowgeometry for which broad iron emission lines can arise in hard and softspectral state. We study an ADAF-type coronal flow, where the ions areviscously heated and electrons receive their heat only by collisions from theions and are Compton cooled by photons from an underlying cool disk. For astrong mass flow in the disk and the resulting strong Compton cooling only avery weak coronal flow is possible. This limitation allows the formation ofADAF-type coronae above weak inner disks in the hard state, but almost rulesthem out in the soft state. The observed hard X-ray luminosity in the softstate, of up to 10% or more of the total flux, indicates that there is aheating process that directly accelerates the electrons. This might point tothe action of magnetic flares of disk magnetic fields reaching into the corona.Such flares have also been proposed by observations of the spectra of X-rayblack hole binaries without a thermal cut-off around 200 keV.

Coronae above accretion disks around black holes: The effect of Compton cooling