Local heating due to convective overshooting and the solar modelling problem

Baraffe, I.; Constantino, T.; Clarke, Joseph H.; Saux, A. Le; Goffrey, T.; Guillet, Thomas; Pratt, J.; Vlaykov, Dimitar

doi:10.1051/0004-6361/202142666

Cited by 5 publications

(1 citation statement)

References 40 publications

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“…However, it should be noticed that the convective entropy flux and kinetic energy flux change the temperature gradient in the overshoot region. The convective entropy flux should increase the temperature gradient a little and make it closer to the adiabatic temperature gradient (e.g., Xiong & Deng 2002;Zhang & Li 2012;Baraffe et al 2022). The kinetic energy flux should decrease the temperature gradient and reduce the size of the convective core (Zhang 2014).…”

Section: Discussionmentioning

confidence: 99%

Core overshoot constrained by the absence of a solar convective core and some solar-like stars

Zhang,

Christensen-Dalsgaard,

2022

Preprint

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Convective-core overshoot mixing is a significant uncertainty in stellar evolution. Because numerical simulations and turbulent convection models predict exponentially decreasing radial rms turbulent velocity, a popular treatment of the overshoot mixing is to apply a diffusion process with exponentially decreasing diffusion coefficient. It is important to investigate the parameters of the diffusion coefficient because they determine the efficiency of the mixing in the overshoot region. In this paper, we have investigated the effects of the core overshoot mixing on the properties of the core in solar models and have constrained the parameters of the overshoot model by using helioseismic inferences and the observation of the solar 8 B neutrino flux. For solar-mass stars, the core overshoot mixing helps to prolong the lifetime of the convective core developed at the ZAMS. If the strength of the mixing is sufficiently high, the convective core in a solar model could survive till the present solar age, leading to large deviations of the sound-speed and density profiles comparing with the helioseismic inferences. The 8 B neutrino flux also favours a radiative solar core. Those provide a constraint on the parameters of the exponential diffusion model of the convective overshoot mixing. A limited asteroseismic investigation of 13 Kepler low-mass stars with 1.0 < M/M ⊙ < 1.5 shows a mass-dependent range of the overshoot parameter. The overshoot mixing processes for different elements are analyzed in detail. It is found that the exponential diffusion overshoot model leads to different effective overshoot mixing lengths for elements with different nuclear equilibrium timescale.

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Section: Discussionmentioning

confidence: 99%

Core overshoot constrained by the absence of a solar convective core and some solar-like stars

Zhang,

Christensen-Dalsgaard,

2022

Preprint

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In-depth analysis of solar models with high-metallicity abundances and updated opacity tables

Buldgen,

Noels,

Scuflaire

et al. 2024

A&A

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As a result of the high-quality constraints available for the Sun, we are able to carry out detailed combined analyses using neutrino, spectroscopic, and helioseismic observations. These studies lay the ground for future improvements of the key physical components of solar and stellar models because ingredients such as the equation of state, the radiative opacities, or the prescriptions for macroscopic transport processes of chemicals are then used to study other stars in the Universe. We study the existing degeneracies in solar models using the recent high-metallicity spectroscopic abundances by comparing them to helioseismic and neutrino data and discuss the effect on their properties of changes in the micro and macro physical ingredients. We carried out a detailed study of solar models computed with a high-metallicity composition from the literature based on averaged 3D models that were claimed to resolve the solar modelling problem. We compared these models to helioseismic and neutrino constraints. The properties of the solar models are significantly affected by the use of the recent OPLIB opacity tables and the inclusion of macroscopic transport. The properties of the standard solar models computed using the OPAL opacities are similar to those for which the OP opacities were used. We show that a modification of the temperature gradient just below the base of the convective zone is required to remove the discrepancies in solar models, particularly in the presence of macroscopic mixing. This can be simulated by a localised increase in the opacity of a few percent. We conclude that the existing degeneracies and issues in solar modelling are not removed by using an increase in the solar metallicity in contradiction to what has been suggested in the recent literature . Therefore, standard solar models cannot be used as an argument for a high-metallicity composition. While further work is required to improve solar models, we note that direct helioseismic inversions indicate a low metallicity in the convective envelope, in agreement with spectroscopic analyses based on full 3D models.

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Asteroseismic modelling of fast rotators and its opportunities for astrophysics

Aerts,

Tkachenko

2024

A&A

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Rotation matters for the life of a star. It causes a multitude of dynamical phenomena in the stellar interior during a star’s evolution, and its effects accumulate until the star dies. All stars rotate at some level, but most of those born with a mass higher than 1.3 times the mass of the Sun rotate rapidly during more than 90% of their nuclear lifetime. Internal rotation guides the angular momentum and chemical element transport throughout the stellar interior. These transport processes change over time as the star evolves. The cumulative effects of stellar rotation and its induced transport processes determine the helium content of the core by the time it exhausts its hydrogen isotopes. The amount of helium at that stage also guides the heavy element yields by the end of the star’s life. A proper theory of stellar evolution and any realistic models for the chemical enrichment of galaxies must be based on observational calibrations of stellar rotation and of the induced transport processes. In the last few years, asteroseismology offers such calibrations for single and binary stars. We review the current status of asteroseismic modelling of rotating stars for different stellar mass regimes in an accessible way for the non-expert. While doing so, we describe exciting opportunities sparked by asteroseismology for various domains in astrophysics, touching upon topics such as exoplanetary science, galactic structure and evolution, and gravitational wave physics to mention just a few. Along the way we provide ample sneak-previews for future ‘industrialised’ applications of asteroseismology to slow and rapid rotators from the exploitation of combined Kepler, Transiting Exoplanet Survey Satellite (TESS), PLAnetary Transits and Oscillations of stars (PLATO), Gaia, and ground-based spectroscopic and multi-colour photometric surveys. We end the review with a list of takeaway messages and achievements of asteroseismology that are of relevance for many fields of astrophysics.

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Local heating due to convective overshooting and the solar modelling problem

Cited by 5 publications

References 40 publications

Core overshoot constrained by the absence of a solar convective core and some solar-like stars

Core overshoot constrained by the absence of a solar convective core and some solar-like stars

In-depth analysis of solar models with high-metallicity abundances and updated opacity tables

Asteroseismic modelling of fast rotators and its opportunities for astrophysics

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