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

Recent simulations find that hot gas accretion onto compact accretors areoften highly turbulent and diskless, and show power-law density profiles withslope $\alpha_\rho\approx-1$. These results are consistent with observationalconstraints, but do not match existing self-similar solutions of radiativelyinefficient accretion flows. We develop a theory for this new class ofaccretion flows, which we dub simple convective accretion flows (SCAFs). We usea set of hydrodynamic simulations to provide a minimalistic example of SCAFs,and develop an analytic theory to explain and predict key flow properties. Wedemonstrate that the turbulence in the flow is driven locally by convection,and argue that radial momentum balance, together with an approximate up-downsymmetry of convective turbulence, yields $\alpha_\rho=-1\pm~{\rm few}~0.1$.Empirically, for an adiabatic hydrodynamic flow with $\gamma\approx 5/3$, weget $\alpha_\rho\approx-0.8$; the resulting accretion rate (relative to theBondi accretion rate), $\dot M/\dot M_{\rm B}\sim (r_{\rm acc}/r_{\rmB})^{0.7}$, agrees very well with the observed accretion rates in Sgr A*, M87*,and a number of wind-fed SgXBs. We also argue that the properties of SCAFs arerelatively insensitive to additional physical ingredients such as cooling andmagnetic field; this explains its common appearance across simulations ofdifferent astrophysical systems.

Simple convective accretion flows (SCAFs): Explaining the $\approx-1$ density scaling of hot accretion flows around compact accretors