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 Plus monthly

Global: Zendy Tools annual

Global: Zendy Tools monthly

Global: Zendy Free Plan

International audienceWe present a possible explanation for the high-frequency quasi-periodic oscillations (QPOs) of microquasars by a magnetohydrodynamic (MHD) instability that combines the physics developed, in different contexts, for the accretion-ejection instability, the Rossby wave instability, and the normal modes of diskoseismic models (which rely on the properties of the relativistic rotation curve in the vicinity of the marginally stable orbit). This instability can appear as modes of azimuthal wavenumbers m=2, 3,... that have very similar pattern speeds ω/m, while the m=1 mode, which would appear as the fundamental of this discrete spectrum, is less unstable. This would readily explain the 2:3 (and sometimes higher) frequency ratio observed between these QPOs. These instabilities form eigenmodes, i.e., standing wave patterns at a constant frequency in the disk; they are strongly unstable and thus do not need an external excitation mechanism to reach high amplitudes. Furthermore, they have the property that a fraction of the accretion energy can be emitted toward the corona; this would explain why these QPOs are seen in a spectral state where Comptonized emission from the corona is always present. Their existence depends critically on the existence of a magnetic structure, formed by poloidal flux advected in the accretion process, in the central region between the disk and the black hole

Accretion‐Ejection Instability, MHD Rossby Wave Instability, Diskoseismology, and the High‐Frequency QPOs of Microquasars