Hypervelocity Planets and Transits Around Hypervelocity Stars

TL;DR

This paper explores the dynamics of planets around hypervelocity stars ejected from the Galactic Centre, revealing potential observational signatures such as transits, collisions, and tidal disruptions.

Contribution

It introduces a novel simulation study of planetary systems around hypervelocity stars, highlighting possible observational phenomena caused by interactions with the central black hole.

Findings

Planets can be ejected at high speeds alongside hypervelocity stars.

Planets may transit their host stars, enabling potential detection.

Tidal disruptions of planets can cause bright flares.

Abstract

The disruption of a binary star system by the massive black hole at the Galactic Centre, SgrA*, can lead to the capture of one star around SgrA* and the ejection of its companion as a hypervelocity star (HVS). We consider the possibility that these stars may have planets and study the dynamics of these planets. Using a direct $N$-body integration code, we simulated a large number of different binary orbits around SgrA*. For some orbital parameters, a planet is ejected at a high speed. In other instances, a HVS is ejected with one or more planets orbiting around it. In these cases, it may be possible to observe the planet as it transits the face of the star. A planet may also collide with its host star. In such cases the atmosphere of the star will be enriched with metals. In other cases, a planet is tidally disrupted by SgrA*, leading to a bright flare.