Accretion inside astrophysical objects: Effects of rotation and viscosity

Subsolar mass black holes could show up in gravitational wave observations in future and near-solar mass black holes might have been involved in the events GW190425 and GW190814. Since they cannot form from the stellar evolution, their creation requires exotic mechanisms. One such mechanism involves the capture of dark matter particles by stellar objects and their thermalization. When the criterion for the collapse of these dark matter particles is satisfied, a tiny endoparasitic black hole (EBH) forms and then it accretes matter from the host. The EBH may transmute the host into a black hole of nearly the same mass as the host or lesser, depending on the type of accretion. We examine this complex and poorly-explored accretion mechanism, considering the effects of rotation and viscosity but ignoring some other effects, such as those of pressure and magnetic field, as the first step. Using a general framework to assess the effects of rotation and viscosity on accretion, we show that the accretion could be stalled in some white dwarfs, but not in neutron stars. The stalled accretion should cause an opening in the host's polar regions, the extent of which depends on the mass and spin of the host.