Schwarzschild and Ledoux are equivalent on evolutionary timescales

Anders, Evan H.; Jermyn, Adam S.; Lecoanet, Daniel; Fraser, Adrian E.; Cresswell, Imogen G.; Joyce, Meridith; Fuentes, J. R.

doi:10.48550/arxiv.2203.06186

Cited by 2 publications

(2 citation statements)

References 35 publications

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“…5) in combination with the Ledoux criterion to define the boundaries of convective instability. This specific approach of treating convection agrees with the results of modern 3D hydrodynamic simulations (Anders et al 2022).…”

Section: Integration Of the Evolutionsupporting

confidence: 86%

Theoretical investigation of the occurrence of tidally excited oscillations in massive eccentric binary systems

Kołaczek-Szymański

Różański

2023

A&A

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Context. Massive and intermediate-mass stars reside in binary systems much more frequently than low-mass stars. At the same time, binaries containing massive main-sequence (MS) component(s) are often characterised by eccentric orbits, and can therefore be observed as eccentric ellipsoidal variables (EEVs). The orbital phase-dependent tidal potential acting on the components of EEV can induce tidally excited oscillations (TEOs), which can affect the evolution of the binary system. Aims. We investigate how the history of resonances between the eigenmode spectra of the EEV components and the tidal forcing frequencies depends on the initial parameters of the system, limiting our study to MS. Each resonance is a potential source of TEO. We are particularly interested in the total number of resonances, their average rate of occurrence and their distribution in time. Methods. We synthesised 20,000 evolutionary models of the EEVs across the MS using Modules for Experiments in Stellar Astrophysics (MESA) software for stellar structure and evolution. We considered a range of masses of the primary component from 5 to 30 M . Later, using the GYRE stellar non-adiabatic oscillations code, we calculated the eigenfrequencies for each model recorded by MESA. We focused only on the l = 2, m = 0, +2 modes, which are suspected of being dominant TEOs. Knowing the temporal changes in the orbital parameters of simulated EEVs and the changes of the eigenfrequency spectra for both components, we were able to determine so-called 'resonance curves', which describe the overall chance of a resonance occurring and therefore of a TEO occurring. We analysed the resonance curves by constructing basic statistics for them and analysing their morphology using machine learning methods, including the Uniform Manifold Approximation and Projection (UMAP) tool.Results. The EEV resonance curves from our sample are characterised by striking diversity, including the occurrence of exceptionally long resonances or the absence of resonances for long evolutionary times. We found that the total number of resonances encountered by components in the MS phase ranges from ∼10 2 to ∼10 3 , mostly depending on the initial eccentricity. We also noticed that the average rate of resonances is about an order of magnitude higher (∼10 2 Myr −1 ) for the most massive components in the assumed range than for EEVs with intermediate-mass stars (∼10 1 Myr −1 ). The distribution of resonances over time is strongly inhomogeneous and its shape depends mainly on whether the system is able to circularise its orbit before the primary component reaches the terminalage MS (TAMS). Both components may be subject to increased resonance rates as they approach the TAMS. Thanks to the lowdimensional UMAP embeddings performed for the resonance curves, we argue that their morphology changes smoothly across the resulting manifold for different initial EEV conditions. The structure of the embeddings allowed us to explore the whole space of resonance curves in terms of their morphology and to iso...

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Section: Integration Of the Evolutionsupporting

confidence: 86%

Theoretical investigation of the occurrence of tidally excited oscillations in massive eccentric binary systems

Kołaczek-Szymański

Różański

2023

A&A

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“…Using models described in Fraser et al (2022), we find that variations of α th between 0.1 and 700 have no effect on our conclusions. The Ledoux criterion for convective stability is used throughout (Ledoux 1951;Anders et al 2022). We improve MESA's default structural and temporal resolutions (mesh_delta_coeff and time_delta_coeff) by a factor of 10 to 100 in our calculations 1 .…”

Section: Theoretical Exploration and Simulationsmentioning

confidence: 99%

Is Thermohaline Mixing the Full Story? Evidence for Separate Mixing Events near the Red Giant Branch Bump

Tayar,

Joyce

2022

Preprint

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The abundances of mixing-sensitive elements including lithium, [C/N], and 12 C/ 13 C are known to change near the red giant branch bump. The explanation most often offered for these alterations is double diffusive thermohaline mixing in the stellar interior. In this analysis, we investigate the ability of thermohaline mixing to explain the observed timing of these chemical depletion events. Recent observational measurements of lithium and [C/N] show that the abundance of lithium decreases before the abundance of [C/N], whereas numerical simulations of the propagation of the thermohaline mixing region computed with MESA show that the synthetic abundances drop simultaneously. We therefore conclude that thermohaline mixing alone cannot explain the distinct events of lithium depletion and [C/N] depletion, as the simultaneity predicted by simulations is not consistent with the observation of separate drops. We thus invite more sophisticated theoretical explanations for the observed temporal separation of these chemical depletion episodes as well as more extensive observational explorations across a range of masses and metallicities.

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Schwarzschild and Ledoux are equivalent on evolutionary timescales

Cited by 2 publications

References 35 publications

Theoretical investigation of the occurrence of tidally excited oscillations in massive eccentric binary systems

Theoretical investigation of the occurrence of tidally excited oscillations in massive eccentric binary systems

Is Thermohaline Mixing the Full Story? Evidence for Separate Mixing Events near the Red Giant Branch Bump

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