2025/07/22 by T. Faran, Eliot Quataert, Faran, Tamar +1
Physics and Astronomy · Computer Science · #Astrophysical Phenomena and Observations #Advanced Image Processing Techniques
paper · pdf · doi:10.48550/arxiv.2507.16893
We study the problem of steady-state spherical accretion onto a black hole, in which the internal energy of the flow is governed by radiation and photon diffusion dominates the energy flux at large radii. In the free-fall limit, the fluid equations can admit two types of solutions for a given accretion rate: (1) accretion flows that become isothermal at large radii and (2) solutions in which the temperature at infinity vanishes as a power law of the radius. Using boundary layer theory, we obtain analytic solutions for the two cases and apply our results to fallback accretion onto a black hole following a failed supernova explosion. We give predictions for the observational signature of fallback accretion using realistic progenitor properties from MESA, both for a fully ionized inflow and for the more realistic case in which recombination/ionization take place due to low photospheric temperatures. The observed fading sources coincident with the failed-supernova candidates in NGC 6946 and M31 are too luminous to be powered by spherical accretion onto newly formed black holes; the observed sources are instead likely due to accretion of the turbulent, convective envelope of the supergiant progenitor.