Accretion onto Reissner–Nordström Naked Singularities

Abstract Nearly every galactic core contains a supermassive compact object, hypothesized to be a Kerr black hole. It was only with the advent of Event Horizon Telescope observations that the predictions of this hypothesis could be observationally tested for our own Galaxy, and the nearby elliptical M87, on spatial scales comparable to the gravitational radius. At the same time, it became possible to test whether alternatives such as naked singularities in general relativity (GR), or similar objects in alternative theories of gravity, are excluded by the data. These and other observational developments renewed interest in non-Kerr spacetime metrics, also in the context of active galactic nuclei at cosmological distances. Recently, we have shown that accreting naked singularities in the Reissner–Nordström (RN) metric of GR tend to produce strong outflows. The geometry and origin of these winds is studied here, and their parameter dependence is investigated. To this end, we perform numerical GR hydrodynamical simulations of accretion of electrically neutral matter in the RN metric and discuss the results in the context of analytic predictions of fluid motion in this spacetime. Comparison of the numerical simulation results for the RN naked singularity with analytically derived equipotential surfaces suggests that gravity has a controlling influence on the flow pattern of the accreting matter.