Choked accretion: from radial infall to bipolar outflows by breaking spherical symmetry

Abstract

Steady state, spherically symmetric accretion flows are well understood in terms of the Bondi solution. Spherical symmetry however, is necessarily an idealized approximation to reality. Here we explore the consequences of deviations away from spherical symmetry, first through a simple analytic model to motivate the physical processes involved, and then through hydrodynamical, numerical simulations of an ideal fluid accreting onto a Newtonian gravitating object. Specifically, we consider axisymmetric, large-scale, small amplitude deviations in the density field such that the equatorial plane is over dense as compared to the polar regions. We find that the resulting polar density gradient dramatically alters the Bondi result and gives rise to steady state solutions presenting bipolar outflows. As the density contrast increases, more and more material is ejected from the system, attaining speeds larger than the local escape velocities for even modest density contrasts. Interestingly, interior to the outflow region, the flow tends locally towards the Bondi solution, with a resulting total mass accretion rate through the inner boundary $choking$ at a value very close to the corresponding Bondi one. Thus, the numerical experiments performed suggest the appearance of a maximum achievable accretion rate, with any extra material being ejected, even for very small departures from spherical symmetry.

10 pages, 8 figures. Accepted for publication in MNRAS. The aztekas code is available at https://github.com/aztekas-code/aztekas-main

References in corpus (6)

• The Supernova -- Gamma-Ray Burst Connection
• Temperature Structure in the Inner Regions of Protoplanetary Disks: Inefficient Accretion Heating Controlled by Nonideal Magnetohydrodynamics
• Axisymmetric Bondi-Hoyle accretion onto a Schwarzschild Black Hole: shock cone vibrations
• One-dimensional radiation-hydrodynamic scaling studies of imploding spherical plasma liners
• Relativistic wind accretion on to a Schwarzschild black hole
• Magnetic Fields in Accretion Disks: A Review

Cited by in corpus (11)

• Jets in Common Envelopes: a low mass main sequence star in a red giant
• Growth of stellar mass black holes in dense molecular clouds and GW190521
• The effect of outflows on CMB bounds from Primordial Black Hole accretion
• Accretion of a Vlasov gas on to a black hole from a sphere of finite radius and the role of angular momentum
• Spherical accretion: Bondi, Michel and rotating black holes
• Outflows from inflows: the nature of Bondi-like accretion
• Choked accretion onto a Kerr black hole
• Bondi-Hoyle-Lyttleton Accretion in a Reactive Medium: Detonation Ignition and a Mechanism for Type Ia Supernovae
• Choked accretion onto Kerr-Sen black holes in Einstein-Maxwell-dilaton-axion gravity
• An XMM-Newton view of the Symbiotic Stars HM Sge, NQ Gem, and PU Vul
• A new hydrodynamic spherical accretion exact solution and its quasi-spherical perturbations