A FUSE Survey of the Rotation Rates of Very Massive Stars in the Small and Large Magellanic Clouds

TL;DR

This study measures the rotation speeds of massive stars in the Milky Way, SMC, and LMC, revealing metallicity influences on stellar rotation and macroturbulence, with implications for stellar evolution models.

Contribution

It provides a comparative analysis of rotational velocities across different metallicity environments using archival FUSE data, testing stellar interior model predictions.

Findings

Some support for metallicity-dependent angular momentum loss.

Similar fractions of fast rotators in evolved and unevolved stars at Galactic metallicity.

Lower macroturbulence in LMC and SMC compared to Galactic stars.

Abstract

We present projected rotational velocity values for 97 Galactic, 55 SMC, and 106 LMC O-B type stars from archival FUSE observations. The evolved and unevolved samples from each environment are compared through the Kolmogorov-Smirnov test to determine if the distribution of equatorial rotational velocities is metallicity dependent for these massive objects. Stellar interior models predict that massive stars with SMC metallicity will have significantly reduced angular momentum loss on the main sequence compared to their Galactic counterparts. Our results find some support for this prediction but also show that even at Galactic metallicity, evolved and unevolved massive stars have fairly similar fractions of stars with large V sin i values. Macroturbulent broadening that is present in the spectral features of Galactic evolved massive stars is lower in the LMC and SMC samples. This suggests the processes that lead to macroturbulence are dependent upon metallicity.