Georges Meynet

Massive star evolution at high metallicity (2006)

We study the effect of wind anisotropies on the stellar evolution leading to collapsars. Rotating models of a 60 M$_\odot$ star with $\Omega/\Omega_{\rm crit}=0.75$ on the ZAMS, accounting for...

Meynet, Georges, Mowlavi, Nami, Maeder, Andre

After a review of the many effects of metallicity on the evolution of rotating and non-rotating stars, we discuss the consequences of a high metallicity on massive star populations and on stellar...

CNO production in first generation stars (2006)

Ekström, Sylvia, Meynet, Georges, Maeder, André

Big Bang nucleosynthesis produces only light elements and the very first generation stars are thus formed from metal-free clouds. They start the production of heavy elements during their life, and...

Mass loss of rotating stars at very low metallicity (2006)

Meynet, Georges, Maeder, Andre, Hirschi, Raphael, Ekstroem, Sylvia, Chiappini, Cristina

Some indirect observations, as the high fraction of Be stars at low metallicity, or the necessity for massive stars to be important sources of primary nitrogen, seem to indicate that very metal poor...

On the Origin of the High Helium Sequence in $\omega$ Centauri (2006)

Maeder, André, Meynet, Georges

The blue Main Sequence (bMS) of $\omega$ Cen implies a ratio of helium to metal enrichment $\Delta Y/\Delta Z \approx 70$, which is a major enigma. We show that rotating models of low metallicity...

Initial conditions for reaching the critical velocity (2006)

Meynet, Georges, Ekström, Sylvia, Maeder, André, Barblan, Fabio

The aim of this paper is to determine the initial rotational velocities required on the ZAMS for single stars to reach the critical velocity, sometimes called the break-up velocity, during the...

Evolution of rotating stars at very low metallicity (2005)

Meynet, Georges, Hirschi, Raphael, Ekstrom, Sylvia, Maeder, Andre

At very low metallicity, the effects of differential rotation have a more important impact on the evolution of stars than at high metallicity. Rotational mixing leads to the production of great...

Single massive stars at the critical rotational velocity: possible links with Be and B[e] stars (2005)

Evolution of the First Stars: CNO Yields and the C-rich Extremely Metal Poor Stars (2005)

Using single star models including the effects of shellular rotation with and without magnetic fields, we show that massive stars at solar metallicity with initial masses lower than about 20-25...

Meynet, Georges, Ekstrom, Sylvia, Maeder, Andre

Rotating massive stars at $Z=10^{-8}$ and $10^{-5}$ lose a great part of their initial mass through stellar winds. The chemical composition of the rotationally enhanced winds of very low $Z$ stars is...

Effects of Rotation on Mass Loss for Population III stars (2005)

Ekström, Sylvia, Meynet, Georges, Maeder, André

The effects of rotation on low-metallicity stellar models are twofold: first, the models reach break-up during main sequence and may lose mass by mechanical process; second, strong internal mixing...

The early star generations: the dominant effect of rotation on the CNO yields (2005)

Meynet, Georges, Ekstrom, Sylvia, Maeder, Andre

We examine the role of rotation on the evolution and chemical yields of very metal--poor stars. The models include the same physics, which was applied successfully at the solar $Z$ and for the SMC,...

Stellar evolution with rotation and magnetic fields:III: The interplay of circulation and dynamo (2005)

Maeder, André, Meynet, Georges

We examine the effects of the magnetic field created by the Tayler--Spruit dynamo in differentially rotating stars. Magnetic fields of the order of a few $10^4$ G are present through most of the...

The Effective Temperature Scale of Galactic Red Supergiants: Cool, But Not As Cool As We Thought (2005)

Levesque, Emily M., Massey, Philip, Olsen, K. A. G., Plez, Bertrand, Josselin, Eric, Maeder, Andre, ...

We use moderate-resolution optical spectrophotometry and the new MARCS stellar atmosphere models to determine the effective temperatures of 74 Galactic red supergiants. From these we find a new...

Rotation and Mixing in Massive Stars: Principles and Uncertainties (2004)

Chemical Abundances and Yields from Massive Stars (2004)

The main instabilities induced by rotation in stellar interiors are described. We derive from first principles the general equation describing the transport of the angular momentum. The case of the...

Maeder, André, Meynet, Georges, Hirschi, Raphael

Stellar rotation produces an internal mixing of the elements due to shear instability and meridional circulation. This leads to observable $N/C$ enhancements in massive stars above about 7--9...

Effects of Rotation on Presupernovae Models (2004)

Meynet, Georges, Hirschi, Raphael, Maeder, André

We show that rotation strongly affects the nature of the supernova progenitor (blue/red supergiant or Wolf--Rayet star), and thus the supernova types. In particular our models well reproduce the...

Evolution of the Most Massive Stars (2004)

Maeder, André, Meynet, Georges, Hirschi, Raphael

We discuss the physics of the $\Omega \Gamma$-- Limit, i.e. when the star is unbound as a result of {\emph{both}} rotation and radiation pressure. We suggest that the $\Omega \Gamma$-- Limit is what...

Evolution at very low and zero Z (2004)

Meynet, Georges, Maeder, André, Ekström, Sylvia

Rotation deeply affects the evolution of very metal poor massive stars. Indeed, even moderately rotating stars reach the break--up limit during the Main--Sequence (MS) phase, they evolve rapidly to...

Stellar evolution with rotation and magnetic fields II: General equations for the transport by Tayler--Spruit dynamo (2004)

Diffusion in stellar interiors: critical tests of three numerical methods (2003)

We further develop the Tayler--Spruit dynamo theory, based on the most efficient instability for generating magnetic fields in radiative layers of differentially rotating stars. We avoid the...

Meynet, Georges, Maeder, Andre, Mowlavi, Nami

We describe and discuss the properties of three numerical methods for solving the diffusion equation for the transport of the chemical species and of the angular momentum in stellar interiors. We...

Pre-suprenova evolution of rotating massive stars (2003)

Hirschi, Raphael, Meynet, Georges, Maeder, Andre, Goriely, Stephane

The Geneva evolutionary code has been modified to study the advanced stages (Ne, O, Si burnings) of rotating massive stars. Here we present the results of four 20 solar mass stars at solar...

Stellar evolution with rotation and magnetic fields:I. The relative importance of rotational and magnetic effects (2003)

Stellar yields with rotation and their effect on chemical evolution models (2003)

We compare the current effects of rotation in stellar evolution to those of the magnetic field created by the Tayler instability. In stellar regions, where magnetic field can be generated by the...

Chiappini, Cristina, Matteucci, Francesca, Meynet, Georges

We compute the evolution of different abundance ratios in the Milky Way (MW) for two different sets of stellar yields. In one of them stellar rotation is taken into account and we investigate its...

Dynamical shear instability (2003)

Hirschi, Raphael, Maeder, Andre, Meynet, Georges

The dynamical shear instability is an important mixing process in the advanced stages of the evolution of massive stars. We calculated different models of 15 Mo with an initial rotational velocity,...

The effects of rotation on Wolf--Rayet stars and on the production of primary nitrogen by intermediate mass stars (2003)

Meynet, Georges, Pettini, Max

We use the rotating stellar models described in the paper by A. Maeder & G. Meynet in this volume to consider the effects of rotation on the evolution of the most massive stars into and during the...

Stellar yields in CNO from rotating stellar models (2003)

Meynet, Georges, Maeder, Andre, Hirschi, Raphael

For $^{12}$C and $^{16}$O, rotating models predict in general enhanced yields. At high metallicity, the carbon and oxygen yields from the very high mass stars, which go through a WR phase, are little...

Evolution of massive stars with rotation and mass loss (2003)

Maeder, André, Meynet, Georges

Rotation appears as a dominant effect in massive star evolution. It largely affects all the model outputs: inner structure, tracks, lifetimes, isochrones, surface compositions, blue to red supergiant...

Stellar evolution with rotation VIII: Models at Z = 10^{-5} and CNO yields for early galactic evolution (2002)

The origin of primary nitrogen in galaxies (2001)

We calculate a grid of star models with and without the effects of axial rotation for stars in the mass range between 2 and 60 M$_{\odot}$ for the metallicity $Z = 10^{-5}$. Star models with initial...

Stellar Evolution with Rotation V: Changes in all the Outputs of Massive Star Models (2000)

We investigate the role of stellar axial rotation on the nitrogen nucleosynthesis at low metallicities Z. For this purpose, we have calculated models with initial masses between 2 and 60 M$_\odot$ at...

Stellar evolution with rotation VI: The Eddington and Omega-limits, the rotational mass loss for OB and LBV stars (2000)

Grids of models for rotating stars are constructed in the range of 9 to 120 M$_{\odot}$ at solar metallicity. The following effects of rotation are included: shellular rotation, new structure...

The evolution of rotating stars (2000)

Several properties of massive stars with large effects of rotation and radiation are studied. We show that there are 2 roots for the equation giving the rotational velocities at break-up: 1) The...

Detection of Wolf-Rayet stars of WN and WC subtype in Super Star Clusters of NGC 5253 (1997)

First, we review the main physical effects to be considered in the building of evolutionary models of rotating stars on the Upper Main-Sequence (MS). The internal rotation law evolves as a result of...

Schaerer, Daniel, Contini, Thierry, Kunth, Daniel, Meynet, Georges

We present spectroscopic observations of the central star clusters in NGC 5253 the aim of which is to search for WC stars. Our observations show the presence of Wolf-Rayet (WR) stars not only of WN...

Detection of Wolf-Rayet stars of WN and WC subtype in Super Star Clusters of NGC 5253 1 (1997)

Daniel Schaerer, Thierry Contini, Daniel Kunth, Georges Meynet

We present spectroscopic observations of the central star clusters in NGC 5253 the aim of which is to search for WC stars. Our observations show the presence of Wolf-Rayet (WR) stars not only of WN...

Rotational mixing in early-type stars: the main-sequence evolution of a 9 Mo star (1996)

Talon, Suzanne, Zahn, Jean-Paul, Maeder, Andre, Meynet, Georges

We describe the main-sequence evolution of a rotating 9 $M_\odot$ star. Its interior rotation profile is determined by the redistribution of angular momentum through the meridian circulation and...

Leitherer, Claus, Alloin, Danielle, Alvensleben, Uta Fritze-V, Gallagher, John, Huchra, John, Matteucci, Francesca, ...

This paper represents a collective effort to provide an extensive electronic database useful for the interpretation of galaxy properties.

Leitherer, Claus, Alloin, Danielle, Alvensleben, Uta Fritze-V, Gallagher, John, Huchra, John, Matteucci, Francesca, ...

This paper represents a collective effort to provide an extensive electronic database useful for the interpretation of galaxy properties.

Leitherer, Claus, Alloin, Danielle, Alvensleben, Uta Fritze-V, Gallagher, John, Huchra, John, Matteucci, Francesca, ...

This paper represents a collective effort to provide an extensive electronic database useful for the interpretation of galaxy properties.