Zum Strahlungsgleichgewicht der Sterne

Vogt, Helle

doi:10.1002/asna.19242231403

Cited by 81 publications

(39 citation statements)

References 1 publication

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“…The rotational instabilities considered are: dynamical shear, secular shear, Eddington-Sweet circulation and the Goldreich-SchubertFricke instability . Two processes dominate rotational mixing in massive stars: Eddington-Sweet circulation, large-scale meridional currents resulting from the thermal imbalance between pole and equator characteristic of rotating stars (von Zeipel 1924;Eddington 1925Eddington , 1926Vogt 1925) and shear mixing, eddies, that can form between two layers of the star rotating at different angular velocity (e.g. Zahn 1974).…”

Section: Stellar Evolution Codementioning

confidence: 99%

Rotational mixing in massive binaries

Mink

Cantiello

Langer

et al. 2009

A&A

267

293

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Models of rotating single stars can successfully account for a wide variety of observed stellar phenomena, such as the surface enhancements of N and He observed in massive main-sequence stars. However, recent observations have questioned the idea that rotational mixing is the main process responsible for the surface enhancements, emphasizing the need for a strong and conclusive test for rotational mixing. We investigate the consequences of rotational mixing for massive main-sequence stars in short-period binaries. In these systems the tides are thought to spin up the stars to rapid rotation, synchronous with their orbital revolution. We use a state-of-the-art stellar evolution code including the effect of rotational mixing, tides, and magnetic fields. We adopt a rotational mixing efficiency that has been calibrated against observations of rotating stars under the assumption that rotational mixing is the main process responsible for the observed surface abundances. We find that the primaries of massive close binaries (M 1 ≈ 20 M , P orb 3 days) are expected to show significant enhancements in nitrogen (up to 0.6 dex in the Small Magellanic Cloud) for a significant fraction of their core hydrogen-burning lifetime. We propose using such systems to test the concept of rotational mixing. As these short-period binaries often show eclipses, their parameters can be determined with high accuracy. For the primary stars of more massive and very close systems (M 1 ≈ 50 M , P orb 2 days) we find that centrally produced helium is efficiently mixed throughout the envelope. The star remains blue and compact during the main sequence evolution and stays within its Roche lobe. It is the less massive star, in which the effects of rotational mixing are less pronounced, which fills its Roche lobe first, contrary to what standard binary evolution theory predicts. The primaries will appear as "Wolf-Rayet stars in disguise": core hydrogen-burning stars with strongly enhanced He and N at the surface. We propose that this evolution path provides an alternative channel for the formation of tight Wolf-Rayet binaries with a main-sequence companion and might explain massive black hole binaries such as the intriguing system M33 X-7.

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Section: Stellar Evolution Codementioning

confidence: 99%

Rotational mixing in massive binaries

Mink

Cantiello

Langer

et al. 2009

A&A

267

293

View full text Add to dashboard Cite

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“…It was first introduced to solve the so-called Von Zeipel paradox by Eddington (1925) and Vogt (1925). When considering the equilibrium of a rotating radiative region, von Zeipel (1924) noticed that "a rotating star cannot achieve simultaneously hydrostatic equilibrium and solid-body rotation".…”

Section: Meridional Circulationmentioning

confidence: 99%

Influence of Rotation on Stellar Evolution

Palacios

2013

EAS Publications Series

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Abstract. The Sun has been known to rotate for more than 4 centuries, and evidence is also available through direct measurements, that almost all stars rotate. In this lecture, I will propose a review of the different physical processes associated to rotation that are expected to impact the evolution of stars. I will describe in detail the way these physical processes are introduced in 1D stellar evolution codes and how their introduction in the modelling has impacted our understanding of the internal structure, nucleosynthesis and global evolution of stars.

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“…It induces large-scale circulations both in radiative and convective zones that simultaneously advect angular momentum, nuclides, and magnetic fields (Eddington 1925;Vogt 1925;Sweet 1950;Mestel 1953;Busse 1982;Zahn 1992;Talon 1997;Maeder & Zahn 1998;Meynet & Maeder 2000;Garaud 2002b;Palacios et al 2003Palacios et al , 2006Rieutord 2006a;Espinosa Lara & Rieutord 2007;Mathis et al 2007). When the star rotates differentially, various instabilities develop (secular and dynamical shear instabilities, baroclinic, and multidiffusive instabilities) that generate hydrodynamical turbulence in radiative zones, in addition to these circulations.…”

Section: The Impact Of Rotation On Stellar Evolutionmentioning

confidence: 99%

Diagnoses to unravel secular hydrodynamical processes in rotating main sequence stars

Decressin

Mathis

Palacios

et al. 2008

A&A

120

138

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Context. Recent progress and constraints brought by helio and asteroseismology call for a better description of stellar interiors and an accurate description of rotation-driven mechanisms in stars. Aims. We present a detailed analysis of the main physical processes responsible for the transport of angular momentum and chemical species in the radiative regions of rotating stars. We focus on cases where meridional circulation and shear-induced turbulence all that are included in the simulations (i.e., no either internal gravity waves nor magnetic fields). We put special emphasis on analysing the angular momentum transport loop and on identifying the contribution of each of the physical process involved. Methods. We develop a variety of diagnostic tools designed to help disentangle the role of the various transport mechanisms. Our analysis is based on a 2-D representation of the secular hydrodynamics, which is treated using expansions in spherical harmonics. By taking appropriate horizontal averages, the problem reduces to one dimension, making it implementable in a 1D stellar evolution code, while preserving the advective character of angular momentum transport. We present a full reconstruction of the meridional circulation and of the associated fluctuations of temperature and mean molecular weight, along with diagnosis for the transport of angular momentum, heat, and chemicals. In the present paper these tools are used to validate the analysis of two main sequence stellar models of 1.5 and 20 M , for which the hydrodynamics has previously been extensively studied in the literature. Results. We obtain a clear visualisation and a precise estimation of the different terms entering the angular momentum and heat transport equations in radiative zones of rotating stars. This enables us to corroborate the main results obtained over the past decade by Zahn, Maeder, and collaborators concerning the secular hydrodynamics of such objects. We focus on the meridional circulation driven by angular momentum losses and structural readjustments. We confirm quantitatively for the first time through detailed computations and separation of the various components that the advection of entropy by this circulation is balanced very well by the barotropic effects and the thermal relaxation during most of the main sequence evolution. This enables us to simplify for the thermal relaxation on this phase. The meridional currents in turn advect heat and generate temperature fluctuations that induce differential rotation through thermal wind, thus closing the transport loop. We plan to make use of our refined diagnosis tools in forthcoming studies of secular (magneto-)hydrodynamics of stars at various evolutionary stages.

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Zum Strahlungsgleichgewicht der Sterne

Cited by 81 publications

References 1 publication

Rotational mixing in massive binaries

Rotational mixing in massive binaries

Influence of Rotation on Stellar Evolution

Diagnoses to unravel secular hydrodynamical processes in rotating main sequence stars

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