On the tidal evolution of the orbits of low-mass satellites around black holes

TL;DR

This paper explores how low-mass objects orbiting black holes evolve due to tidal forces, highlighting the role of plunging orbits and their potential to cause short, energetic accretion events linked to Galactic flares.

Contribution

It introduces the concept of tidal orbital evolution around black holes, emphasizing the significance of plunging orbits and their impact on accretion phenomena.

Findings

Plunging orbits lead to tidal energy release on black hole timescales.

Tidal interactions can drive small bodies onto unstable orbits.

Energy released matches the magnitude of Galactic flares.

Abstract

Low-mass satellites, like asteroids and comets, are expected to be present around the black hole at the Galactic center. We consider small bodies orbiting a black hole, and we study the evolution of their orbits due to tidal interaction with the black hole. In this paper we investigate the consequences of the existence of plunging orbits when a black hole is present. We are interested in finding the conditions that exist when capture occurs. The main difference between the Keplerian and black hole cases is in the existence of plunging orbits. Orbital evolution, leading from bound to plunging orbits, goes through a final unstable circular orbit. On this orbit, tidal energy is released on a characteristic black hole timescale. This process may be relevant for explaining how small, compact clumps of material can be brought onto plunging orbits, where they may produce individual short duration accretion events. The available energy and the characteristic timescale are consistent with energy released and the timescale typical of Galactic flares.