Synergies between Asteroseismology and Three-dimensional Simulations of Stellar Turbulence

Arnett, W. David; Moravveji, E.

doi:10.3847/2041-8213/aa5cb0

Cited by 18 publications

(22 citation statements)

References 33 publications

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“…Note that rotation-induced shear mixing (Edelmann et al, 2017) plays a similar role as the convection-induced shear and both lead to smoother profiles at boundaries. Using a diffusion coefficient, which is exponentially decaying from the convective boundary in 1D codes following multi-D simulations of outer convective regions (Herwig, 2000;Freytag, Ludwig and Steffen, 1996) commonly used in MESA (Paxton et al, 2011), enables the reproduction of asteroseismic constraints and leads to abundance profiles at boundaries, which are comparable to those of 3D simulations (Arnett and Moravveji, 2017). This exponentially-decaying mixing leads to larger convective cores like penetrative overshoot or entrainment but at a rate/extent which may not be correct.…”

Section: Discussionmentioning

confidence: 99%

Dependence of convective boundary mixing on boundary properties and turbulence strength

Cristini

Hirschi

Meakin

et al. 2019

Monthly Notices of the Royal Astronomical Society

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Convective boundary mixing is one of the major uncertainties in stellar evolution. In order to study its dependence on boundary properties and turbulence strength in a controlled way, we computed a series of 3D hydrodynamical simulations of stellar convection during carbon burning with a varying boosting factor of the driving luminosity. Our 3D implicit large eddy simulations were computed with the prompi code. We performed a mean field analysis of the simulations within the Reynolds-averaged Navier-Stokes framework. Both the vertical RMS velocity within the convective region and the bulk Richardson number of the boundaries are found to scale with the driving luminosity as expected from theory: ∝ 1/3 and Ri B ∝ −2/3 , respectively. The positions of the convective boundaries were estimated through the composition profiles across them, and the strength of convective boundary mixing was determined by analysing the boundaries within the framework of the entrainment law. We find that the entrainment is approximately inversely proportional to the bulk Richardson number, Ri B (∝ Ri − B , ∼ 0.75). Although the entrainment law does not encompass all the processes occurring at boundaries, our results support the use of the entrainment law to describe convective boundary mixing in 1D models, at least for the advanced phases. The next steps and challenges ahead are also discussed.

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Section: Discussionmentioning

confidence: 99%

Dependence of convective boundary mixing on boundary properties and turbulence strength

Cristini

Hirschi

Meakin

et al. 2019

Monthly Notices of the Royal Astronomical Society

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“…Even with the computational power currently available, stellar evolution models necessarily remain 1D simplifications of 3D gaseous spheres (e.g., Cristini et al 2016). The first steps of a solid calibration of stellar interiors from the bridging of 3D simulations and 1D stellar models are being taken from gravitymode asteroseismology for stars in the mass range of our work (Arnett & Moravveji 2017). The level of sophistication adopted in 1D numerical models of stars with a convective core is diverse, even for the simplest phase of core-hydrogen burning upon which we focus here.…”

Section: D Stellar Evolution Modelsmentioning

confidence: 99%

The mass discrepancy in intermediate- and high-mass eclipsing binaries: The need for higher convective core masses

Tkachenko

Pavlovski

Johnston

et al. 2020

A&A

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Context. Eclipsing, spectroscopic double-lined binary star systems (SB2) are excellent laboratories for calibrating theories of stellar interior structure and evolution. Their precise and accurate masses and radii measured from binary dynamics offer model-independent constraints and challenge current theories of stellar evolution. Aims. We aim to investigate the mass discrepancy in binary stars. This is the significant difference between stellar components' masses measured from binary dynamics and those inferred from models of stellar evolution via positions of the components in the T eff -log g Kiel diagram. We study the effect of near-core mixing on the mass of the convective core of the stars and interpret the results in the context of the mass discrepancy. Methods. We fit stellar isochrones computed from a grid of mesa stellar evolution models to a homogeneous sample of eleven highmass binary systems. Two scenarios are considered, where individual stellar components of a binary system are treated independent of each other and where they are forced to have the same age and initial chemical composition. We also study the effect of the microturbulent velocity and turbulent pressure on the atmosphere model structure and stellar spectral lines, and its link with the mass discrepancy.Results. We find that the mass discrepancy is present in our sample and that it is anti-correlated with the surface gravity of the star. No correlations are found with other fundamental and atmospheric parameters, including the stellar mass. The mass discrepancy can be partially accounted for by increasing the amount of near-core mixing in stellar evolution models. We also find that ignoring the microturbulent velocity and turbulent pressure in stellar atmosphere models of hot evolved stars results in overestimation of their effective temperature by up to 8%. Together with enhanced near-core mixing, this can almost entirely account for the ∼30% mass discrepancy found for the evolved primary component of V380 Cyg. Conclusions. We find a strong link between the mass discrepancy and the convective core mass. The mass discrepancy can be solved by considering the combined effect of extra near-core boundary mixing and consistent treatment in the spectrum analysis of hot evolved stars. Our binary modelling results in convective core masses between 17 and 35% of the stellar mass, in excellent agreement with results from gravity-mode asteroseismology of single stars. This implies larger helium core masses near the end of the main sequence than anticipated so far.

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“…Determining precisely how α MLT may vary, and according to which stellar properties, is an ongoing task. Efforts by e.g., Arnett & Moravveji (2017) and Mosumgaard et al (2017) will aid in having 3D simulations further inform our 1D models. Convection is another uncertain aspect in stellar modeling, alongside the uncertainties of stellar rotation.…”

Section: Effect Of Mixing Length On the Red Clumpmentioning

confidence: 99%

Age Determinations of the Hyades, Praesepe, and Pleiades via MESA Models with Rotation

Gossage

Conroy

Dotter

et al. 2018

ApJ

137

123

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The Hyades, Praesepe, and Pleiades are well studied stellar clusters that anchor important secondary stellar age indicators. Recent studies have shown that main sequence turn off-based ages for these clusters may depend on the degree of rotation in the underlying stellar models. Rotation induces structural instabilities that can enhance the chemical mixing of a star, extending its fuel supply. In addition, rotation introduces a modulation of the star's observed magnitude and color due to the effects of gravity darkening. We aim to investigate the extent to which stellar rotation affects the age determination of star clusters. We utilize the MESA stellar evolution code to create models that cover a range of rotation rates corresponding to Ω/Ω c = 0.0 to 0.6 in 0.1 dex steps, allowing the assessment of variations in this dimension. The statistical analysis package, MATCH, is employed to derive ages and metallicities by fitting our MESA models to Tycho B T , V T and 2MASS J, K s colormagnitude diagrams. We find that the derived ages are relatively insensitive to the effects of rotation. For the Hyades, Praesepe, and Pleiades, we derive ages based on synthetic populations that model a distribution of rotation rates or a fixed rate. Across each case, derived ages tend to agree roughly within errors, near 680, 590, and 110 − 160 Myr for the Hyades, Praesepe, and Pleiades, respectively. These ages are in agreement with Li depletion boundary-based ages and previous analyses that used non-rotating isochrones. Our methods do not provide a strong constraint on the metallicities of these clusters.

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Synergies between Asteroseismology and Three-dimensional Simulations of Stellar Turbulence

Cited by 18 publications

References 33 publications

Dependence of convective boundary mixing on boundary properties and turbulence strength

Dependence of convective boundary mixing on boundary properties and turbulence strength

The mass discrepancy in intermediate- and high-mass eclipsing binaries: The need for higher convective core masses

Age Determinations of the Hyades, Praesepe, and Pleiades via MESA Models with Rotation

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