Hoyle-Lyttleton Accretion in Three Dimensions

TL;DR

This study uses high-resolution 3D simulations to analyze Hoyle-Lyttleton accretion, revealing that the flows are more stable and axisymmetric than previously thought, with minimal angular momentum transfer.

Contribution

The paper demonstrates that higher spatial resolution reveals more stable and axisymmetric accretion flows, challenging earlier findings of instability and disk formation.

Findings

Flows are highly axisymmetric at higher resolution.

Mass accretion rate is extremely steady for larger accretors.

Smaller accretors exhibit a breathing mode with 20% modulation.

Abstract

We investigate the stability of gravitational accretion of an ideal gas onto a compact object moving through a uniform medium at Mach 3. Previous three-dimensional simulations have shown that such accretion is not stable, and that strong rotational 'disk-like' flows are generated and accreted on short time scales. We re-address this problem using overset spherical grids that provide a factor of seven improvement in spatial resolution over previous simulations. With our higher spatial resolution we found these 3D accretion flows remained remarkably axisymmetric. We examined two cases of accretion with different sized accretors. The larger accretor produced very steady flow, with the mass accretion rate varying by less than 0.02% over 30 flow times. The smaller accretor exhibited an axisymmetric breathing mode that modulated the mass accretion rate by a constant 20%. Nonetheless, the flow remained highly axisymmetric with only negligible accretion of angular momentum in both cases.