Gaia and HST astrometry of the very massive $\sim$150 $M_\odot$ candidate runaway star VFTS682

TL;DR

This study uses Gaia and HST astrometry to analyze the motion of the very massive star VFTS682, suggesting it is a runaway star ejected from the R136 cluster, which has implications for star formation theories.

Contribution

First astrometric analysis combining Gaia and HST data to investigate the runaway status of a very massive star, providing evidence supporting its ejection from a central cluster.

Findings

VFTS682 has a projected velocity of 38 ± 17 km/s relative to R136.

Astrometric data suggest VFTS682 is a runaway star ejected from the cluster.

Supports theories that massive stars can be dynamically ejected from clusters.

Abstract

How very massive stars form is still an open question in astrophysics. VFTS682 is among the most massive stars known, with an inferred initial mass of $\sim$150 $M_\odot$ . It is located in 30 Doradus at a projected distance of 29 pc from the central cluster R136. Its apparent isolation led to two hypotheses: either it formed in relative isolation or it was ejected dynamically from the cluster. We investigate the kinematics of VFTS682 as obtained by Gaia and Hubble Space Telescope astrometry. We derive a projected velocity relative to the cluster of $38 \pm 17 \mathrm{km \ s^{-1}}$ (1$\sigma$ confidence interval). Although the error bars are substantial, two independent measures suggest that VFTS682 is a runaway ejected from the central cluster. This hypothesis is further supported by a variety of circumstantial clues. The central cluster is known to harbor other stars more massive than 150 $M_\odot$ of similar spectral type and recent astrometric studies on VFTS16 and VFTS72 provide direct evidence that the cluster can eject some of its most massive members, in agreement with theoretical predictions. If future data confirm the runaway nature, this would make VFTS682 the most massive runaway star known to date.