Origin of the S Stars in the Galactic Center

TL;DR

This paper proposes that the S stars near the Galactic Center originate from the dynamical interaction and disruption of stellar binaries in two precessing disks, explaining their high eccentricities and the presence of hypervelocity stars.

Contribution

It introduces a new dynamical mechanism involving disk interactions and Kozai effects to explain the origin of S stars and hypervelocity stars.

Findings

S stars result from binary disruptions due to high eccentricities

Dynamical interactions in stellar disks can produce hypervelocity stars

High eccentricity orbits are achieved through precession and Kozai interactions

Abstract

Over the last 15 years, around a hundred very young stars have been observed in the central parsec of our Galaxy. While the presence of young stars forming one or two stellar disks at approx. 0.1 pc from the supermassive black hole (SMBH) can be understood through star formation in accretion disks, the origin of the S stars observed a factor of 10 closer to the SMBH has remained a major puzzle. Here we show the S stars to be a natural consequence of dynamical interaction of two stellar disks at larger radii. Due to precession and Kozai interaction, individual stars achieve extremely high eccentricities at random orientation. Stellar binaries on such eccentric orbits are disrupted due to close passages near the SMBH, leaving behind a single S star on a much tighter orbit. The remaining star may be ejected from the vicinity of the SMBH, thus simultaneously providing an explanation for the observed hypervelocity stars in the Milky Way halo.