Accretion of a Vlasov gas by a Kerr black hole

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Hauptverfasser: Mach, Patryk, Momennia, Mehrab, Sarbach, Olivier
Format: Preprint
Veröffentlicht: 2025
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author Mach, Patryk
Momennia, Mehrab
Sarbach, Olivier
author_facet Mach, Patryk
Momennia, Mehrab
Sarbach, Olivier
contents We investigate the accretion of a collisionless, relativistic kinetic gas by a rotating Kerr black hole, assuming that at infinity the state of the gas is described by a distribution function depending only on the energy of the particles. Neglecting the self-gravity of the gas, we show that relevant physical observables, including the particle current density and the accretion rates associated with the mass, the energy, and the angular momentum, can be expressed in the form of closed integrals that can be evaluated numerically or approximated analytically in the slow-rotation limit. The accretion rates are computed in this manner for both monoenergetic particles and the Maxwell-Jüttner distribution and compared with the corresponding results in the non-rotating case. We show that the angular momentum accretion rate decreases the absolute value of the black hole spin parameter. It is also found that the rotation of the black hole has a small but non-vanishing effect on the mass and the energy accretion rates, which is remarkably well described by an analytic calculation in the slow-rotation approximation to quadratic order in the rotation parameter. The effects of rotation on the morphology of the accretion flow are also analyzed.
format Preprint
id arxiv_https___arxiv_org_abs_2508_04783
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Accretion of a Vlasov gas by a Kerr black hole
Mach, Patryk
Momennia, Mehrab
Sarbach, Olivier
General Relativity and Quantum Cosmology
High Energy Astrophysical Phenomena
Mathematical Physics
We investigate the accretion of a collisionless, relativistic kinetic gas by a rotating Kerr black hole, assuming that at infinity the state of the gas is described by a distribution function depending only on the energy of the particles. Neglecting the self-gravity of the gas, we show that relevant physical observables, including the particle current density and the accretion rates associated with the mass, the energy, and the angular momentum, can be expressed in the form of closed integrals that can be evaluated numerically or approximated analytically in the slow-rotation limit. The accretion rates are computed in this manner for both monoenergetic particles and the Maxwell-Jüttner distribution and compared with the corresponding results in the non-rotating case. We show that the angular momentum accretion rate decreases the absolute value of the black hole spin parameter. It is also found that the rotation of the black hole has a small but non-vanishing effect on the mass and the energy accretion rates, which is remarkably well described by an analytic calculation in the slow-rotation approximation to quadratic order in the rotation parameter. The effects of rotation on the morphology of the accretion flow are also analyzed.
title Accretion of a Vlasov gas by a Kerr black hole
topic General Relativity and Quantum Cosmology
High Energy Astrophysical Phenomena
Mathematical Physics
url https://arxiv.org/abs/2508.04783