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Classical Be stars, the "e" standing for the presence of spectroscopic line emission, are main sequence stars of spectral type B that are able to form a gaseous disk in Keplerian motion from star-ejected matter. The main driver of this…
Stellar models provide a vital basis for many aspects of astronomy and astrophysics. Recent advances in observational astronomy -- through asteroseismology, precision photometry, high-resolution spectroscopy, and large-scale surveys -- are…
Rotation and mass loss are crucially interlinked properties of massive stars, strongly affecting their evolution and ultimate fate. Massive stars rotating near their breakup limit shed mass centrifugally, creating Be stars with…
This paper investigates the spin-up of a mass-accreting star in a close binary system passing through the first stage of mass exchange in the Hertzsprung gap. Inside an accreting star, angular momentum is carried by meridional circulation…
To fully understand the Be star phenomenon, one must have a reasonable degree of knowledge about the star beneath the disk, which is often found to be rapidly rotating. Rapid rotation complicates modelling because fundamental properties…
Classical Be stars are fast rotating, near main sequence B-type stars. The rotation and the presence of circumstellar discs profoundly modify the observables of active Be stars. Our goal is to infer stellar and disc parameters, as well as…
A rotating star may be modeled as a continuous system of particles attracted to each other by gravity and with a given total mass and prescribed angular velocity. Mathematically this leads to the Euler-Poisson system. We prove an existence…
Context. The mechanism of disk formation around fast-rotating Be stars is not well understood. In particular, it is not clear which mechanisms operate, in addition to fast rotation, to produce the observed variable ejection of matter. The…
B-type stars are known to rotate at various velocities, including very fast rotators near the critical velocity as the Be stars. In this paper, we provide stellar models covering the mass range between 1.7 to 15 Msun, which includes the…
In preparation for the COROT space mission, we determined the fundamental parameters (spectral type, temperature, gravity, vsini) of the Be stars observable by COROT in its seismology fields (64 Be stars). We applied a careful and detailed…
Hierarchical triple stars are ideal laboratories for studying the interplay between orbital dynamics and stellar evolution. Both stellar wind mass loss and three-body dynamics cooperate to destabilise triples, which can lead to a variety of…
Be stars are rapidly rotating B main sequence stars, which show line emission due to an outflowing disc. By studying the evolution of rotating single star models, we can assess their contribution to the observed Be star populations. We…
New constraints on stellar models are provided by large surveys of massive stars, interferometric observations and asteroseismology. After a review of the main results so far obtained, we present new results from rotating models and discuss…
After a brief introduction into the asteroseismic modelling of stars, we provide a compilation of the current seismic estimates of the core overshooting parameter and of the rotational frequency of single and binary massive stars. These…
Stellar structure and evolution theory is one of the basis in modern astronomy. Stellar inner structures and their evolutionary states can be precisely tested by asteroseismology, since the inner information is brought to the stellar…
Be stars are thought to be fast rotating stars surrounded by an equatorial disc. The formation, structure and evolution of the disc are still not well understood. In the frame of single star models, it is expected that the surface of an…
Accurate determinations of masses and radii in binary stars, along with estimates of the effective temperatures, metallicities, and other properties, have long been used to test models of stellar evolution. As might be expected,…
Achernar, the closest and brightest classical Be star, presents rotational flattening, gravity darkening, occasional emission lines due to a gaseous disk, and an extended polar wind. It is also a member of a close binary system with an…
Multiple systems play an important role in the evolution of star clusters. First we discuss several formation mechanisms which depend on the presence of binaries, either primordial or of dynamical origin. Hierarchical configurations are…
Be stars are a class of rapidly rotating B stars with circumstellar disks that cause Balmer and other line emission. There are three possible reasons for the rapid rotation of Be stars: they may have been born as rapid rotators, spun up by…