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Convective overshoot mixing is a critical ingredient of stellar structure models, but is treated in most cases by ad hoc extensions of the mixing-length theory for convection. Advanced theories which are both more physical and numerically…

Solar and Stellar Astrophysics · Physics 2022-11-16 Felix Ahlborn , Friedrich Kupka , Achim Weiss , Martin Flaskamp

Shell convection driven by nuclear burning in a stellar core is a common hydrodynamic event in the evolution of many types of stars. We encounter and simulate this convection (i) in the helium core of a low-mass red giant during core helium…

Solar and Stellar Astrophysics · Physics 2015-05-27 Miroslav Mocak , Ewald Muller , Lionel Siess

In this contribution we present initial results of a study on convective boundary mixing (CBM) in massive stellar models using the GENEVA stellar evolution code. Before undertaking costly 3D hydrodynamic simulations, it is important to…

Solar and Stellar Astrophysics · Physics 2015-06-23 Andrea Cristini , Raphael Hirschi , Cyril Georgy , Casey Meakin , David Arnett , Maxime Viallet

Extending our recent studies of two-dimensional stellar convection to 3D, we compare three-dimensional hydrodynamic simulations to identically set-up two-dimensional simulations, for a realistic pre-main sequence star. We compare…

Solar and Stellar Astrophysics · Physics 2020-07-01 J. Pratt , I. Baraffe , T. Goffrey , C. Geroux , T. Constantino , D. Folini , R. Walder

Supermassive stars are Population III stars with masses exceeding $10^4\,M_{\odot}$ that could be the progenitors of the first supermassive black holes. Their interiors are in a regime where radiation pressure dominates the equation of…

Solar and Stellar Astrophysics · Physics 2023-03-29 Simon Blouin , Huaqing Mao , Tyrone E. Woods , Pavel Denissenkov , Paul R. Woodward , Falk Herwig

Broadening and asymmetry of spectral lines in slowly rotating late A-type stars provide evidence for high-amplitude convective motions. The properties of turbulence observed in the A-star atmospheres are not understood theoretically and…

Astrophysics · Physics 2015-06-24 O. Kochukhov , B. Freytag , N. Piskunov , M. Steffen

Winds from young massive stars contribute a large amount of energy to their host molecular clouds. This has consequences for the dynamics and observable structure of star-forming clouds. In this paper, we present radiative…

Astrophysics of Galaxies · Physics 2020-12-09 Sam Geen , Rebekka Bieri , Joakim Rosdahl , Alex de Koter

In spite of the great effort made in the last decades to improve our understanding of stellar evolution, significant uncertainties remain due to our poor knowledge of some complex physical processes that require an empirical calibration,…

Solar and Stellar Astrophysics · Physics 2015-06-22 Alessandro Bressan , Leo Girardi , Paola Marigo , Philip Rosenfield , Jing Tang

We use the 3D stellar structure code DJEHUTY to model the ingestion of protons into the intershell convection zone of a 1 solar mass asymptotic giant branch star of metallicity Z=10^-4. We have run two simulations: a low resolution one of…

Solar and Stellar Astrophysics · Physics 2015-05-30 Richard J. Stancliffe , David S. P. Dearborn , John C. Lattanzio , Stuart A. Heap , Simon W. Campbell

Three-dimensional (3D), time dependent numerical simulations, of flow of matter in stars, now have sufficient resolution to be fully turbulent. The late stages of the evolution of massive stars, leading up to core collapse to a neutron star…

Solar and Stellar Astrophysics · Physics 2014-01-30 W. David Arnett , Casey Meakin , Maxime Viallet

This paper describes the first steps of development of a new multidimensional time implicit code devoted to the study of hydrodynamical processes in stellar interiors. The code solves the hydrodynamical equations in spherical geometry and…

Instrumentation and Methods for Astrophysics · Physics 2015-05-27 M. Viallet , I. Baraffe , R. Walder

We present a statistical analysis of turbulent convection in stars within our Reynolds-Averaged Navier Stokes (RANS) framework in spherical geometry which we derived from first principles. The primary results reported in this document…

Solar and Stellar Astrophysics · Physics 2014-01-22 Miroslav Mocák , Casey Meakin , Maxime Viallet , David Arnett

We perform two-dimensional numerical simulations of core convection for zero-age-main-sequence stars covering a mass range from 3 $M_\odot$ to 20 $M_\odot$. The simulations are performed with the fully compressible time-implicit code MUSIC.…

Solar and Stellar Astrophysics · Physics 2023-01-18 I. Baraffe , J. Clarke , A. Morison , D. G. Vlaykov , T. Constantino , T. Goffrey , T. Guillet , A. Le Saux , J. Pratt

The treatment of mixing processes is still one of the major uncertainties in 1D stellar evolution models. This is mostly due to the need to parametrize and approximate aspects of hydrodynamics in hydrostatic codes. In particular, the effect…

Solar and Stellar Astrophysics · Physics 2017-08-02 Philipp V. F. Edelmann , Friedrich K. Roepke , Raphael Hirschi , Cyril Georgy , Samuel Jones

The extent of mixed regions around convective zones is one of the biggest uncertainties in stellar evolution. 1D overshooting descriptions introduce a free parameter ($f_{ov}$) that is in general not well constrained from observations.…

Solar and Stellar Astrophysics · Physics 2021-03-08 Johann Higl , Ewald Mueller , Achim Weiss

In Pop III stellar models convection-induced mixing between H- and He-rich burning layers can induce a burst of nuclear energy and thereby substantially alter the subsequent evolution and nucleosynthesis in the first massive stars. We…

Solar and Stellar Astrophysics · Physics 2020-11-04 Ondrea Clarkson , Falk Herwig

Degenerate ignition of helium in low-mass stars at the end of the red giant branch phase leads to dynamic convection in their helium cores. One-dimensional (1D) stellar modeling of this intrinsically multi-dimensional dynamic event is…

Solar and Stellar Astrophysics · Physics 2015-05-18 Miroslav Mocak , Simon W. Campbell , Ewald Mueller , Konstantinos Kifonidis

Evolved stars are among the largest and brightest stars and they are ideal targets for the new generation of sensitive, high resolution instrumentation that pro- vides spectrophotometric, interferometric, astrometric, and imaging…

Solar and Stellar Astrophysics · Physics 2014-10-16 A. Chiavassa , B. Freytag

Models of core-collapse supernova explosions powered by the neutrino-driven mechanism have matured considerable in recent years. Explosions at the low-mass end of the progenitor spectrum can routinely be simulated in 1D, 2D, and 3D and…

Solar and Stellar Astrophysics · Physics 2016-10-05 B. Müller

Evolved stars are among the largest and brightest stars and they are ideal targets for the new generation of sensitive, high resolution instrumentation that provides spectrophotometric, interferometric, astrometric, and imaging observables.…

Solar and Stellar Astrophysics · Physics 2015-12-16 A. Chiavassa , B. Freytag