# Testing the stability of supersonic ionized Bondi accretion flows with radiation hydrodynamics

## TL;DR

This paper analyzes the stability of ionized Bondi accretion flows onto young stellar objects, revealing marginal stability and recurring collapse of HII regions through analytic models and 1D radiation hydrodynamics simulations.

## Contribution

It provides a new analytic steady-state solution for ionized accretion flows and demonstrates their marginal stability and instability via simulations.

## Key findings

- Steady-state two-temperature solution predicts compact HII regions.
- Ionization self-consistently treated leads to marginal stability.
- HII regions tend to recur and collapse over time.

## Abstract

We investigate the general stability of 1D spherically symmetric ionized Bondi accretion onto a massive object in the specific context of accretion onto a young stellar object. We first derive a new analytic expression for a steady state two temperature solution that predicts the existence of compact and hypercompact HII regions. We then show that this solution is only marginally stable if ionization is treated self-consistently. This leads to a recurring collapse of the HII region over time. We derive a semi-analytic model to explain this instability, and test it using spatially converged 1D radiation hydrodynamical simulations. We discuss the implications of the 1D instability on 3D radiation hydrodynamics simulations of supersonic accreting flows.