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Present grids of stellar atmosphere models are the workhorses in interpreting stellar observations, and determining their fundamental parameters. These models rely on greatly simplified models of convection, however, lending less predictive…

Solar and Stellar Astrophysics · Physics 2015-06-15 Regner Trampedach , Martin Asplund , Remo Collet , Åke Nordlund , Robert F. Stein

Theoretical atmosphere models provide the basis for a variety of applications in astronomy. In simplified one-dimensional (1D) atmosphere models, convection is usually treated with the mixing length theory despite its well-known…

Solar and Stellar Astrophysics · Physics 2015-06-17 Zazralt Magic , Remo Collet , Martin Asplund

We present the Stagger-grid, a comprehensive grid of time-dependent, 3D hydrodynamic model atmospheres for late-type stars with realistic treatment of radiative transfer, covering a wide range in stellar parameters. This grid of 3D models…

Solar and Stellar Astrophysics · Physics 2015-06-15 Z. Magic , R. Collet , M. Asplund , R. Trampedach , W. Hayek , A. Chiavassa , R. F. Stein , Å. Nordlund

Three-dimensional (3D) radiative hydrodynamic model atmospheres of metal-poor late-type stars are characterized by cooler upper photospheric layers than their 1D counterparts. This property of 3D models can dramatically affect elemental…

Solar and Stellar Astrophysics · Physics 2015-05-27 R. Collet , W. Hayek , M. Asplund , Å. Nordlund , R. Trampedach , B. Gudiksen

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

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

Radiative hydrodynamic simulations of solar and stellar surface convection have become an important tool for exploring the structure and gas dynamics in the envelopes and atmospheres of late-type stars and for improving our understanding of…

Solar and Stellar Astrophysics · Physics 2015-06-03 B. Beeck , R. Collet , M. Steffen , M. Asplund , R. H. Cameron , B. Freytag , W. Hayek , H. -G. Ludwig , M. Schüssler

Recently 3D hydrodynamical simulations of stellar surface convection have become feasible thanks to advances in computer technology and efficient numerical algorithms. Available observational diagnostics indicate that these models are…

Astrophysics · Physics 2007-05-23 Martin Asplund , Remo Collet

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

Context. The surface structures and dynamics of cool stars are characterized by the presence of convective motions and turbulent flows which shape the emergent spectrum. Aims. We used realistic three-dimensional radiative hydrodynamical…

Solar and Stellar Astrophysics · Physics 2018-03-14 A. Chiavassa , L. Casagrande , R. Collet , Z. Magic , L. Bigot , F. Thevenin , M. Asplund

We analyze stellar convection with the aid of 3D hydrodynamic simulations, introducing the turbulent cascade into our theoretical analysis. We devise closures of the Reynolds-decomposed mean field equations by simple physical modeling of…

Astrophysics · Physics 2011-02-11 David Arnett , Casey Meakin , P. A. Young

Hydrodynamical simulations of stellar interactions require stable models of stars as initial conditions. Such initial models, however, are difficult to construct for giant stars because of the wide range in spatial scales of the hydrostatic…

Solar and Stellar Astrophysics · Physics 2017-02-22 Sebastian T. Ohlmann , Friedrich K. Roepke , Rüdiger Pakmor , Volker Springel

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

The dynamics and thermal structure of the surface layers of stars with outer convection zones can be studied in some detail by means of numerical simulations of time-dependent compressible convection. In an effort to investigate the…

Astrophysics · Physics 2007-05-23 Matthias Steffen

High-resolution images of the solar surface show a granulation pattern of hot rising and cooler downward-sinking material -- the top of the deep-reaching solar convection zone. Convection plays a role for the thermal structure of the solar…

Solar and Stellar Astrophysics · Physics 2011-12-14 Bernd Freytag , Matthias Steffen , Hans-Günter Ludwig , Sven Wedemeyer-Böhm , Werner Schaffenberger , Oskar Steiner

We perform a calibration of the mixing length of convection in stellar structure models against realistic 3D radiation-coupled hydrodynamics (RHD) simulations of convection in stellar surface layers, determining the adiabat deep in…

Solar and Stellar Astrophysics · Physics 2015-06-23 Regner Trampedach , Robert F. Stein , Jørgen Christensen-Dalsgaard , Åke Nordlund , Martin Asplund

1D stellar evolution calculations produce uncertain predictions for quantities like the age, core mass, core compactness, and nucleo-synthetic yields; a key source of uncertainty is the modeling of interfaces between regions that are…

Standard 1D stellar evolution model has poor descriptions of the near-surface layers of stars, and this can be improved by using the atmosphere model computed from 3D hydrodynamical simulations. In this work, we validated the model…

Solar and Stellar Astrophysics · Physics 2025-12-02 Zhikai Li , Tanda Li , Yixiao Zhou , Shaolan Bi

Several parametrizations for overshooting in 1D stellar evolution calculations coexist in the literature. These parametrizations are used somewhat arbitrarily in stellar evolution codes, based on what works best for a given problem, or even…

Solar and Stellar Astrophysics · Physics 2015-08-05 Maxime Viallet , Casey Meakin , Vincent Prat , David Arnett

Developing a theory of low-mass star formation ($\sim 0.1$ to 3~M$_{\odot}$) remains one of the most elusive and important goals of theoretical astrophysics. The star-formation process is the outcome of the complex dynamics of interstellar…

Astrophysics · Physics 2007-05-23 Richard I. Klein , Shu-ichiro Inutsuka , Paolo Padoan , Kohji Tomisaka