Angular Momentum Transport in Stellar Interiors

Aerts, C.; Mathis, S.; Rogers, T. M.

doi:10.1146/annurev-astro-091918-104359

Cited by 261 publications

(308 citation statements)

References 255 publications

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“…In fact, presently-used prescriptions for the angular momentum transport in stars are challenged by asteroseismic constraints (see Cantiello et al 2014;Maeder & Meynet 2014 and recently Aerts et al 2019), showing that the presentlyused prescriptions are not efficient enough to reproduce the contrast between the rotation of the core and the rotation of the envelope in sub giants and in red giant stars 12 . Fuller et al (2019) and Ma & Fuller (2019) proposed a modification of the Spruit-Tayler dynamo allowing to obtain a better agreement with the observations; however, according to Eggenberger et al (2019), some physics is still missing for providing a satisfactory fit of all the observational constraints.…”

Section: Surface Angular Velocitymentioning

confidence: 99%

The effects of surface fossil magnetic fields on massive star evolution – II. Implementation of magnetic braking in mesa and implications for the evolution of surface rotation in OB stars

Keszthelyi

Meynet

Shultz

et al. 2020

Monthly Notices of the Royal Astronomical Society

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The time evolution of angular momentum and surface rotation of massive stars is strongly influenced by fossil magnetic fields via magnetic braking. We present a new module containing a simple, comprehensive implementation of such a field at the surface of a massive star within the Modules for Experiments in Stellar Astrophysics (mesa) software instrument. We test two limiting scenarios for magnetic braking: distributing the angular momentum loss throughout the star in the first case, and restricting the angular momentum loss to a surface reservoir in the second case. We perform a systematic investigation of the rotational evolution using a grid of OB star models with surface magnetic fields (M = 5 − 60 M , Ω/Ω crit = 0.2 − 1.0, B p = 1 − 20 kG). We then employ a representative grid of B-type star models (M = 5, 10, 15 M , Ω/Ω crit = 0.2, 0.5, 0.8, B p = 1, 3, 10, 30 kG) to compare to the results of a recent selfconsistent analysis of the sample of known magnetic B-type stars. We infer that magnetic massive stars arrive at the zero age main sequence with a range of rotation rates, rather than with one common value. In particular, some stars are required to have close-to-critical rotation at the ZAMS. However, magnetic braking yields surface rotation rates converging to a common low value, making it difficult to infer the initial rotation rates of evolved, slowly-rotating stars.

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Section: Surface Angular Velocitymentioning

confidence: 99%

The effects of surface fossil magnetic fields on massive star evolution – II. Implementation of magnetic braking in mesa and implications for the evolution of surface rotation in OB stars

Keszthelyi

Meynet

Shultz

et al. 2020

Monthly Notices of the Royal Astronomical Society

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“…This strong transport leads to a uniform rotation in the case of the Sun down to 0.2 R (García et al 2007) and to weak differential rotation in other stars (e.g., Mosser et al 2012;Deheuvels et al 2012Deheuvels et al , 2014Kurtz et al 2014;Saio et al 2015;Murphy et al 2016;Spada et al 2016;Van Reeth et al 2016Aerts et al 2017;Gehan et al 2018;Ouazzani et al 2019). Four main mechanisms that transport angular momentum and mix chemicals are present in stellar radiation zones (e.g., Maeder 2009;Mathis 2013;Aerts et al 2019, and references therein): instabilities of the differential rotation (e.g., Zahn 1983Zahn , 1992, stable and unstable magnetic fields (e.g., Spruit 1999;Fuller et al 2019), internal gravity waves (e.g., Zahn et al 1997;Talon & Charbonnel 2005;Pinçon et al 2017), and largescale meridional circulations (e.g., Zahn 1992;Maeder & Zahn 1998;. Important progress has been made in their modeling during the last two decades.…”

Section: Introductionmentioning

confidence: 99%

Horizontal shear instabilities in rotating stellar radiation zones

Park

Prat

Mathis

2020

A&A

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Context. Stellar interiors are the seat of efficient transport of angular momentum all along with their evolution. In this context, understanding the dependence of the turbulent transport triggered by the instabilities of the vertical and horizontal shears of the differential rotation in stellar radiation zones as a function of their rotation, stratification, and thermal diffusivity is mandatory. Indeed, it constitutes one of the cornerstones of the rotational transport and mixing theory which is implemented in stellar evolution codes to predict the rotational and chemical evolutions of stars. Aims. We investigate horizontal shear instabilities in rotating stellar radiation zones by considering the full Coriolis acceleration with both the dimensionless horizontal Coriolis componentf and the vertical component f . Methods. We performed a linear stability analysis using linearized equations derived from the Navier-Stokes and heat transport equations in the rotating non-traditional f -plane. We considered a horizontal shear flow with a hyperbolic tangent profile as the base flow. The linear stability was analyzed numerically in wide ranges of parameters, and we performed an asymptotic analysis for large vertical wavenumbers using the Wentzel-Kramers-Brillouin-Jeffreys (WKBJ) approximation for non-diffusive and highly diffusive fluids. Results. As in the traditional f -plane approximation, we identify two types of instabilities: the inflectional and inertial instabilities. The inflectional instability is destabilized asf increases and its maximum growth rate increases significantly, while the thermal diffusivity stabilizes the inflectional instability similarly to the traditional case. The inertial instability is also strongly affected; for instance, the inertially unstable regime is also extended in the non-diffusive limit as 0 < f < 1 +f 2 /N 2 , where N is the dimensionless Brunt-Väisälä frequency. More strikingly, in the high-thermal-diffusivity limit, it is always inertially unstable at any colatitude θ except at the poles (i.e., 0 • < θ < 180 • ). We also derived the critical Reynolds numbers for the inertial instability using the asymptotic dispersion relations obtained from the WKBJ analysis. Using the asymptotic and numerical results, we propose a prescription for the effective turbulent viscosities induced by the inertial and inflectional instabilities that can be possibly used in stellar evolution models. The characteristic time of this turbulence is short enough so that it is efficient to redistribute angular momentum and mix chemicals in stellar radiation zones.

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“…In general, both element and angular momentum transport processes throughout a star are poorly calibrated (Aerts et al 2019). It is a well-known shortcoming of most 1D theoretical descriptions of convection that convective boundaries are not well described (Hirschi et al 2014).…”

Section: Introductionmentioning

confidence: 99%

Modelling of the B-type binaries CW Cephei and U Ophiuchi

Johnston

Pavlovski

Tkachenko

2019

A&A

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Context. Intermediate-mass stars are often overlooked. They are not supernova progenitors, but still host convective cores and complex atmospheres that require computationally expensive treatment. This means that there is a general lack of this class of stars modelled by state-of-the-art stellar structure and evolution codes. Aims. We used high-quality spectroscopy to update the dynamically obtained stellar parameters and to produce a new evolutionary assessment of the bright B0.5+B0.5 and B5V+B5V binary systems CW Cep and U Oph. Methods. We used new spectroscopy obtained with the Hermes spectrograph to revisit the photometric binary solution of the two systems. The updated mass ratio and effective temperatures are incorporated to obtain new dynamical masses for the primary and secondary. With these data we performed evolutionary modelling using isochrone-clouds to investigate the core properties of these stars. Results. We report the first abundances for CW Cep and U Oph, and we report an updated dynamical solution for the two systems. We find that we cannot uniquely constrain the amount of core boundary mixing in any of the stars we consider. Instead, we report their core masses and compare our results to previous studies. Conclusions. We find that the per-cent level precision on fundamental stellar quantities are accompanied with core mass estimates to a precision between ∼5% and 15%. We find that differences in analysis techniques can lead to substantially different evolutionary modelling results, which calls for the compilation of a homogeneously analysed sample to draw inferences on internal physical processes.

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Angular Momentum Transport in Stellar Interiors

Cited by 261 publications

References 255 publications

The effects of surface fossil magnetic fields on massive star evolution – II. Implementation of magnetic braking in mesa and implications for the evolution of surface rotation in OB stars

The effects of surface fossil magnetic fields on massive star evolution – II. Implementation of magnetic braking in mesa and implications for the evolution of surface rotation in OB stars

Horizontal shear instabilities in rotating stellar radiation zones

Modelling of the B-type binaries CW Cephei and U Ophiuchi

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