On the behaviour of B and Be stars at low metallicity

TL;DR

This study investigates how low metallicity environments like the Magellanic Clouds influence the rotation, evolution, and pulsation behaviors of B and Be stars, revealing new insights into their physical properties.

Contribution

It provides new observational data on B and Be stars at low metallicity, analyzing their rotation, evolution, and pulsation characteristics, which were previously less understood.

Findings

Metallicity affects the rotation rates of B and Be stars.

First detection of multi-periodic pulsations in SMC Be stars.

Proportions of Be to B stars vary with environment.

Abstract

We present new results obtained with the VLT GIRAFFE for a large sample of B and Be stars belonging to the Magellanic Clouds, i.e. at low metallicity. First, we show the effects of the metallicity of the environment on their rotation (linear, angular, and at the ZAMS). Second, we present the analysis of the effects of metallicity and evolution on the appearance of Be stars. We also new present results about the proportions of Be stars to B stars. Third, by cross-correlation with large photometric surveys such as MACHO and OGLE, we report on the detection for the first time of short-term multi-periodicity in 9 Be stars in the Small Magellanic Cloud, which can be interpreted in terms of pulsations.