A hypervelocity star with a Magellanic origin

TL;DR

This study uses Gaia data to trace the origins of hypervelocity stars, revealing that one such star likely originated from the Large Magellanic Cloud, implying the presence of a massive black hole there.

Contribution

It provides the first direct evidence of a massive black hole in the LMC by tracing the hypervelocity star HVS3 back to its origin.

Findings

HVS3 originated from the LMC about 21 million years ago.

HVS3's velocity suggests a Hills mechanism origin involving a massive black hole.

The LMC hosts a black hole of at least 4,000 to 10,000 solar masses.

Abstract

Using proper motion measurements from Gaia DR2, we probe the origin of 26 previously known hypervelocity stars (HVSs) around the Milky Way. We find that a significant fraction of these stars have a high probability of originating close to the Milky Way centre, but there is one obvious outlier. HVS3 is highly likely to be coming almost from the centre of the Large Magellanic Cloud (LMC). During its closest approach, $21.1^{+6.1}_{-4.6}$ Myr ago, it had a relative velocity of $870^{+69}_{-66}$ kms$^{-1}$ with respect to the LMC. This large kick velocity is only consistent with the Hills mechanism, requiring a massive black hole at the centre of the LMC. This provides strong direct evidence that the LMC itself harbours a massive black hole of at least $4\times 10^3 -10^4 M_\odot$.