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We study turbulent convection during the core helium flash close to its peak by comparing the results of two and three-dimensional hydrodynamic simulations. We use a multidimensional Eulerian hydrodynamics code based on state-of-the-art…

天体物理学 · 物理学 2015-05-13 M. Mocak , E. Mueller , A. Weiss , K. Kifonidis

Convection plays an essential role in the emerging intensity for many stars that will be observed by Gaia. Convective-related surface structures affect the shape, shift, and asymmetry of absorption lines, the phocentric and photometric…

太阳与恒星天体物理 · 物理学 2011-12-13 A. Chiavassa , L. Bigot , F. Thevenin , R. Collet , G. Jasniewicz , Z. Magic , M. Asplund

Our knowledge of stellar evolution is driven by one-dimensional (1D) simulations. 1D models, however, are severely limited by uncertainties on the exact behaviour of many multi-dimensional phenomena occurring inside stars, affecting their…

太阳与恒星天体物理 · 物理学 2023-05-26 F. Rizzuti , R. Hirschi , W. D. Arnett , C. Georgy , C. Meakin , A. StJ. Murphy , T. Rauscher , V. Varma

One of the largest sources of uncertainty in stellar models is caused by the treatment of convection in stellar envelopes. One dimensional stellar models often make use of the mixing length or equivalent approximations to describe…

太阳与恒星天体物理 · 物理学 2016-05-04 Joel D. Tanner , Sarbani Basu , Pierre Demarque

We present the results of realistic, 3D, hydrodynamical, simulations of surface convection in red giant stars with varying effective temperatures and metallicities. We use the convection simulations as time-dependent, hydrodynamical, model…

天体物理学 · 物理学 2007-11-21 R. Collet , M. Asplund , R. Trampedach

The global scales of solar convection are studied through three-dimensional simulations of compressible convection carried out in spherical shells of rotating fluid which extend from the base of the convection zone to within 15 Mm of the…

天体物理学 · 物理学 2009-11-13 Mark S. Miesch , Allan Sacha Brun , Marc L. Derosa , Juri Toomre

We present results from three-dimensional hydrodynamic simulations of the high redshift collapse of pregalactic clouds including feedback effects from a soft H2 photodissociating UV radiation field. The simulations use an Eulerian adaptive…

天体物理学 · 物理学 2009-10-31 Marie E. Machacek , Greg L. Bryan , Tom Abel

We perform for the first time a 3D hydrodynamics simulation of the evolution of the last minutes pre-collapse of the oxygen shell of a fast-rotating massive star. This star has an initial mass of 38 M$_\odot$, a metallicity of $\sim$1/50…

Three-dimensional numerical simulations of solar surface magnetoconvection using realistic model physics are conducted. The thermal structure of convective motions into the upper radiative layers of the photosphere, the main scales of…

太阳与恒星天体物理 · 物理学 2015-05-13 Sergey D. Ustyugov

We have developed a multidimensional radiation hydrodynamics code to simulate the interaction of radial stellar pulsation and convection for full amplitude pulsating models. Convection is computed using large eddy simulations. Here we…

太阳与恒星天体物理 · 物理学 2014-03-05 Christopher M. Geroux , Robert G. Deupree

We used a series of COBOLD hydrodynamical model atmospheres covering stellar objects from white dwarfs to red giants to derive theoretical estimates of the photometric and photocentric stellar variability in wavelength-integrated light…

天体物理学 · 物理学 2007-05-23 F. Svensson , H. -G. Ludwig

Based on detailed 2D and 3D numerical radiation-hydrodynamics (RHD) simulations of time-dependent compressible convection, we have studied the dynamics and thermal structure of the convective surface layers of a prototypical late-type…

天体物理学 · 物理学 2009-11-07 H. -G. Ludwig , F. Allard , P. H. Hauschildt

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…

太阳与恒星天体物理 · 物理学 2015-06-23 Regner Trampedach , Robert F. Stein , Jørgen Christensen-Dalsgaard , Åke Nordlund , Martin Asplund

The origin of the near-ultraviolet and optical continuum radiation in flares is critical for understanding particle acceleration and impulsive heating in stellar atmospheres. Radiative-hydrodynamic simulations in 1D have shown that high…

太阳与恒星天体物理 · 物理学 2018-01-10 Adam F. Kowalski , Joel C. Allred

This paper presents a new code for performing multidimensional radiation hydrodynamic (RHD) simulations on parallel computers involving anisotropic radiation fields and nonequilibrium effects. The radiation evolution modules described here…

天体物理学 · 物理学 2009-11-07 John C. Hayes , Michael L. Norman

We construct a 3D radiative-hydrodynamic model atmosphere of parameters Teff = 4820 K, log g = 4.5, and solar chemical composition. The theoretical line profiles computed with this model are asymmetric, with their bisectors having a…

太阳与恒星天体物理 · 物理学 2015-05-13 I. Ramirez , C. Allende Prieto , L. Koesterke , D. L. Lambert , M. Asplund

An approximate method for solving the rate equations for the hydrogen populations was extended and implemented in the three-dimensional radiation (magneto-)hydrodynamics code CO5BOLD. The method is based on a model atom with six energy…

天体物理学 · 物理学 2009-11-11 Jorrit Leenaarts , Sven Wedemeyer-Boehm

Recently, new solar model atmospheres have been developed to replace classical 1D LTE hydrostatic models and used to for example derive the solar chemical composition. We aim to test various models against key observational constraints. In…

太阳与恒星天体物理 · 物理学 2015-06-15 Tiago M. D. Pereira , Martin Asplund , Remo Collet , Irina Thaler , Regner Trampedach , Jorrit Leenaarts

A new three-dimensional model of the solar photosphere is presented in this paper and made publicly available to the community. This model has the peculiarity that it has been obtained by inverting spectro-polarimetric observations, rather…

太阳与恒星天体物理 · 物理学 2015-05-27 H. Socas-Navarro

The early phase of the hydrodynamic evolution following collision of two stars is analyzed. Two strong shocks propagate at a constant velocity (which is a small fraction of the velocity of the approaching stars) from the contact surface…

高能天体物理现象 · 物理学 2015-06-17 Doron Kushnir , Boaz Katz