Transfusionen des Humanen

Maeder, Dominik

doi:10.14361/transcript.9783839421604.321

Cited by 44 publications

(58 citation statements)

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“…That rotation appears to suppress mixing is at odds with expectations from standard models with rotational mixing: Faster rotating models should experience more mixing and therefore more lithium depletion. This can be seen, for example, in the evolution models from Charbonnel & Talon (2005) that match the range of lithium observed in clusters at various ages but where the lithium-rotation correlation is the opposite of that observed, as well as the models from Amard et al 2016 that included a number of different treatments for determining turbu-lent diffusion coefficients from Zahn (1992), Maeder (1997), Talon & Zahn (1997), and Mathis et al (2004). The hydrostatic effects from including the centrifugal force from rotation do not explain the observed trend, and the discrepancy is worsened when rotational mixing is included (Mendes et al 1999).…”

Section: Introductionmentioning

confidence: 84%

Suppression of lithium depletion in young low-mass stars from fast rotation

Constantino,

Baraffe,

Goffrey

et al. 2021

Preprint

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We compute rotating 1D stellar evolution models that include a modified temperature gradient in convection zones and criterion for convective instability inspired by rotating 3D hydrodynamical simulations performed with the music code. In those 3D simulations we found that convective properties strongly depend on the Solberg-Høiland criterion for stability. We therefore incorporated this into 1D stellar evolution models by replacing the usual Schwarzschild criterion for stability and also modifying the temperature gradient in convection zones. We computed a grid of 1D models between 0.55 and 1.2 stellar masses from the pre-main sequence to the end of main sequence in order to study the problem of lithium depletion in low-mass main sequence stars. This is an ideal test case because many of those stars are born as fast rotators and the rate of lithium depletion is very sensitive to the changes in the stellar structure. Additionally, observations show a correlation between slow rotation and lithium depletion, contrary to expectations from standard models of rotationally driven mixing. By suppressing convection, and therefore decreasing the temperature at the base of the convective envelope, lithium burning is strongly quenched in our rapidly rotating models to an extent sufficient to account for the lithium spread observed in young open clusters.

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Section: Introductionmentioning

confidence: 84%

Suppression of lithium depletion in young low-mass stars from fast rotation

Constantino,

Baraffe,

Goffrey

et al. 2021

Preprint

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“…The production of selements is highly sensitive to the amount of 22 Ne available, which in turn, depends on stellar evolution inputs such as the way rotational mixing (also convection) is treated in the code. Different recipes exist in the literature for the horizontal diffusion (Zahn 1992;Maeder 2003;Mathis et al 2004) and the shear diffusion coefficients (Talon & Zahn 1997;Maeder 1997;Maeder et al 2013) that govern the transport of chemical elements (see Meynet et al 2013, for a review). Different combinations of these coefficients will lead to a higher/smaller production of extra 22 Ne, hence a possibly different production of s-elements.…”

Section: Model Uncertaintiesmentioning

confidence: 99%

Non standard s-process in massive rotating stars. Yields of $10-150$ $M_{\odot}$ models at $Z=10^{-3}$

Choplin,

Hirschi,

Meynet

et al. 2018

Preprint

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Context. Recent studies show that rotation significantly affects the s-process in massive stars. Aims. We provide tables of yields for non-rotating and rotating massive stars between 10 and 150 M at Z = 10 −3 ([Fe/H] = −1.8). Tables for different mass cuts are provided. The complete s-process is followed during the whole evolution with a network of 737 isotopes, from Hydrogen to Polonium. Methods. A grid of stellar models with initial masses of 10, 15, 20, 25, 40, 60, 85, 120 and 150 M and with an initial rotation rate of both 0 or 40% of the critical velocity was computed. Three extra models were computed in order to investigate the effect of faster rotation (70% of the critical velocity) and of a lower 17 O(α, γ) reaction rate. Results. At the considered metallicity, rotation has a strong impact on the production of s-elements for initial masses between 20 and 60 M . In this range, the first s-process peak is boosted by 2 − 3 dex if rotation is included. Above 60 M , s-element yields of rotating and non-rotating models are similar. Increasing the initial rotation from 40 % to 70 % of the critical velocity enhances the production of 40 Z 60 elements by ∼ 0.5 − 1 dex. Adopting a reasonably lower 17 O(α, γ) rate in the fast rotating model (70 % of the critical velocity) boosts again the yields of s-elements with 55 Z 82 by about 1 dex. In particular, a modest amount of Pb is produced. Together with s-elements, some light elements (particularly fluorine) are strongly overproduced in rotating models.

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“…where we have approximated r/h as unity because this is the case in the bulk of the star. Now note that the turbulent viscosity is of order (Maeder 1997)…”

Section: Appendix A: Role Of Differential Rotationmentioning

confidence: 99%

Enhanced Rotational Mixing in the Radiative Zones of Massive Stars

Jermyn,

Tout,

Chitre

2018

Preprint

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Convection in the cores of massive stars becomes anisotropic when they rotate. This anisotropy leads to a misalignment of the thermal gradient and the thermal flux, which in turn results in baroclinicity and circulation currents in the upper radiative zone. We show that this induces a much stronger meridional flow in the radiative zone than previously thought. This drives significantly enhanced mixing, though this mixing does not necessarily reach the surface. The extra mixing takes on a similar form to convective overshooting, and is relatively insensitive to the rotation rate above a threshold, and may help explain the large overshoot distances inferred from observations. This has significant consequences for the evolution of these stars by enhancing core-envelope mixing.

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Transfusionen des Humanen

Cited by 44 publications

References 0 publications

Suppression of lithium depletion in young low-mass stars from fast rotation

Suppression of lithium depletion in young low-mass stars from fast rotation

Non standard s-process in massive rotating stars. Yields of $10-150$ $M_{\odot}$ models at $Z=10^{-3}$

Enhanced Rotational Mixing in the Radiative Zones of Massive Stars

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