Secular Evolution Of Binaries Near Massive Black Holes: Formation of compact binaries, merger/collision products and G2-like objects

TL;DR

This paper studies how binaries near massive black holes evolve under secular perturbations, leading to increased interactions, mergers, and the formation of exotic objects like G2-like clouds, impacting stellar evolution in nuclear clusters.

Contribution

It introduces a coupled model of secular and tidal evolution of binaries near MBHs, highlighting their role in forming various astrophysical phenomena.

Findings

Binaries tend to become eccentric or short-period due to MBH perturbations.

Enhanced binary interactions lead to mergers, blue stragglers, and X-ray binaries.

Possible formation of G2-like objects from binary mergers or collisions.

Abstract

Here we discuss the evolution of binaries around MBH in nuclear stellar clusters. We focus on their secular evolution due to the perturbation by the MBH, while simplistically accounting for their collisional evolution. Binaries with highly inclined orbits in respect to their orbit around the MBH are strongly affected by secular processes, which periodically change their eccentricities and inclinations (e.g. Kozai--Lidov cycles). During periapsis approach, dissipative processes such as tidal friction may become highly efficient, and may lead to shrinkage of a binary orbit and even to its merger. Binaries in this environment can therefore significantly change their orbital evolution due to the MBH third-body perturbative effects. Such orbital evolution may impinge on their later stellar evolution. Here we follow the secular dynamics of such binaries and its coupling to tidal evolution, as well as the stellar evolution of such binaries on longer time-scales. We find that stellar binaries in the central parts of NSCs are highly likely to evolve into eccentric and/or short period binaries, and become strongly interacting binaries either on the main sequence (at which point they may even merge), or through their later binary stellar evolution. The central parts of NSCs therefore catalyze the formation and evolution of strongly interacting binaries, and lead to the enhanced formation of blue stragglers, X-ray binaries, gravitational wave sources and possible supernova progenitors. Induced mergers/collisions may also lead to the formation of G2-like cloud-like objects such as the one recently observed in the Galactic center.