Andre Maeder

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...

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...

The Effective Temperatures and Physical Properties of Magellanic Cloud Red Supergiants: The Effects of Metallicity (2006)

Levesque, Emily M., Massey, Philip, Olsen, K. A. G., Plez, Bertrand, Meynet, George, Maeder, Andre

We use the MARCS stellar atmosphere to derive the physical properties of 36 red supergiants (RSGs) in the LMC, and 39 RSGs in the SMC using moderate-resolution optical spectrophotometry (4000-9000A)...

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...

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,...

Oscillations on the star Procyon (2005)

Bouchy, Francois, Maeder, Andre, Mayor, Michel, Megevand, Denis, Pepe, Francesco, Sosnowska, Danuta

Stars are sphere of hot gas whose interiors transmit acoustic waves very efficiently. Geologists learn about the interior structure of Earth by monitoring how seismic waves propagate through it and,...

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)

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

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...

Bouchy, Francois, Maeder, Andre, Mayor, Michel, Megevand, Denis, Pepe, Francesco, Sosnowska, Danuta

Stars are sphere of hot gas whose interiors transmit acoustic waves very efficiently. Geologists learn about the interior structure of Earth by monitoring how seismic waves propagate through it and,...

Bouchy, Francois, Maeder, Andre, Mayor, Michel, Megevand, Denis, Pepe, Francesco, Sosnowska, Danuta

Stars are sphere of hot gas whose interiors transmit acoustic waves very efficiently. Geologists learn about the interior structure of Earth by monitoring how seismic waves propagate through it and,...

Bouchy, Francois, Maeder, Andre, Mayor, Michel, Megevand, Denis, Pepe, Francesco, Sosnowska, Danuta

Stars are sphere of hot gas whose interiors transmit acoustic waves very efficiently. Geologists learn about the interior structure of Earth by monitoring how seismic waves propagate through it and,...

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

Bouchy, Francois, Maeder, Andre, Mayor, Michel, Megevand, Denis, Pepe, Francesco, Sosnowska, Danuta

Stars are sphere of hot gas whose interiors transmit acoustic waves very efficiently. Geologists learn about the interior structure of Earth by monitoring how seismic waves propagate through it and,...

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)

Dynamical shear instability (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...

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,...

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...

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...

On the Formation of Massive Stars by Accretion (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...

Norberg, Peder, Maeder, Andre

(Abriged) At present, there are two scenarios for the formation of massive stars: 1) The accretion scenario and 2) The coalescence scenario, which implies the merging of intermediate mass stars. We...

The evolution of rotating stars (2000)