Hypervelocity stars from young stellar clusters in the Galactic Centre

TL;DR

This paper explores how close interactions between the Milky Way's central black hole and passing young stellar clusters can produce hypervelocity stars, including single, binary, and merged stars, revealing their origins and properties.

Contribution

It introduces a model for hypervelocity star production from cluster-black hole interactions, highlighting the effects of binary fraction and mass segregation.

Findings

HVSs are generated during cluster pericentre passage.

Binary fraction influences the binary HVSs produced.

Merged binaries can become blue stragglers traveling out of the Galaxy.

Abstract

The enormous velocities of the so called hypervelocity stars (HVSs) derive, likely, from close interactions with massive black holes, binary stars encounters or supernova explosions. In this paper, we investigate the origin of hypervelocity stars as consequence of the close interaction between the Milky Way central massive black hole and a passing-by young stellar cluster. We found that both single and binary HVSs may be generated in a burst-like event, as the cluster passes near the orbital pericentre. High velocity stars will move close to the initial cluster orbital plane and in the direction of the cluster orbital motion at the pericentre. The binary fraction of these HVS jets depends on the primordial binary fraction in the young cluster. The level of initial mass segregation determines the value of the average mass of the ejected stars. Some binary stars will merge, continuing their travel across and out of the Galaxy as blue stragglers.