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

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.