On the Social Traits of Luminous Blue Variables

TL;DR

This study investigates the spatial distribution and velocities of Luminous Blue Variables across several galaxies, finding they are associated with young stars and are not runaway stars, supporting their classification as evolved massive stars.

Contribution

The paper provides a comprehensive analysis of LBV locations and velocities in multiple galaxies, challenging previous claims of LBV isolation and runaway status.

Findings

LBVs are associated with luminous young stars and supergiants.

LBV velocities are consistent with their galactic positions, not runaway stars.

Classical LBVs resemble late O-type stars in distribution, less luminous LBVs resemble red supergiants.

Abstract

In a recent paper, Smith and Tombleson (2015) state that the Luminous Blue Variables (LBVs) in the Milky Way and the Magellanic Clouds are isolated; that they are not spatially associated with young O-type stars. They propose a novel explanation that would overturn the standard view of LBVs. In this paper we test their hypothesis for the LBVs in M31 and M33 as well as the LMC and SMC. In M31 and M33, the LBVs are associated with luminous young stars and supergiants appropriate to their luminosities and positions on the HR Diagram. Moreover, in the Smith and Tombleson scenario most of the LBVs should be runaway stars, but the stars' velocities are consistent with their positions in the respective galaxies. In the Magellanic Clouds, those authors' sample was a mixed population. We reassess their analysis, removing seven stars that have no clear relation to LBVs. When we separate the more massive classical and the less luminous LBVs, the classical LBVs have a distribution similar to the late O-type stars, while the less luminous LBVs have a distribution like the red supergiants. None of the confirmed LBVs have high velocities or are candidate runaway stars. These results support the accepted description of LBVs as evolved massive stars that have shed a lot of mass, and are now close to their Eddington limit.