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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

Context: Calculating stellar pulsations requires a sufficient accuracy to match the quality of the observations. Many current pulsation codes apply a second order finite-difference scheme, combined with Richardson extrapolation to reach…

太阳与恒星天体物理 · 物理学 2015-06-16 D. R. Reese

In microscopic mechanical systems interactions between elastic structures are often mediated by the hydrodynamics of a solvent fluid. At microscopic scales the elastic structures are also subject to thermal fluctuations. Stochastic…

软凝聚态物质 · 物理学 2023-02-28 Paul J. Atzberger

A computationally efficient model is introduced to account for the sub-grid scale velocities of tracer particles dispersed in statistically homogeneous and isotropic turbulent flows. The model embeds the multi-scale nature of turbulent…

流体动力学 · 物理学 2015-06-18 I. M. Mazzitelli , F. Toschi , A. S. Lanotte

We perform three-dimensional hydrodynamic simulations of two idealized regimes of stellar convection: a cooling-driven model (Model C) and an entropy-gradient-driven model (Model S). The two regimes exhibit striking contrasts: while Model S…

太阳与恒星天体物理 · 物理学 2025-11-18 Youhei Masada , Tomoya Takiwaki , Nobumitsu Yoko

Understanding the origin and evolution of carbon-enhanced metal-poor (CEMP) stars is key to tracing the Galaxy's early chemical enrichment. We investigate how realistic 3D radiation-hydrodynamics (RHD) model atmospheres affect carbon…

In this review presented at the Symposium A stellar journey in Uppsala, June 2008, I give my account of the historical development of the MARCS code from the first version published in 1975 and its premises to the 2008 grid. It is shown…

天体物理学 · 物理学 2009-11-13 Bertrand Plez

We present first results from three-dimensional radiation magnetohydrodynamic simulations of M-type dwarf stars with CO5BOLD. The local models include the top of the convection zone, the photosphere, and the chromosphere. The results are…

太阳与恒星天体物理 · 物理学 2013-01-10 S. Wedemeyer , H. -G. Ludwig , O. Steiner

We discuss three issues in the context of three-dimensional (3D) hydrodynamical model atmospheres for late-type stars, related to spectral line shifts, radiative transfer in metal-poor 3D models, and the solar oxygen abundance. We include a…

天体物理学 · 物理学 2009-11-13 Hans-G. Ludwig , Matthias Steffen

A new three-dimensional (3D) multiphase computational fluid dynamics (CFD) model for adsorption physics in packed beds of spherical beads is developed and validated. The model is constituted at a macroscopic scale that integrates new…

流体动力学 · 物理学 2026-03-24 Mohamad Najib Nadamani , Mostafa Safdari Shadloo , Talib Dbouk

We present a new method for replacing the outermost layers of stellar models with interpolated atmospheres based on results from 3D simulations, in order to correct for structural inadequacies of these layers. This replacement is known as…

We have calculated a grid of more than 700 model atmospheres valid for a wide range of parameters encompassing the coolest known M~dwarfs, M~subdwarfs and brown dwarf candidates: $1500\le \teff \le 4000\,$K, $3.5\le \log(g)\le 5.5$, and…

天体物理学 · 物理学 2009-10-28 France Allard , Peter H. Hauschildt

We present an update of the grid of detailed atmosphere models and homogeneous synthetic spectra for hot, high-gravity subdwarf stars. High-resolution spectra and synthetic photometry were calculated in the wavelength range 1,000 \r{A} -…

太阳与恒星天体物理 · 物理学 2023-07-18 Thayse A. Pacheco , Ronaldo S. Levenhagen , Marcos P. Diaz , Paula R. T. Coelho

The first paper of this series [J. Chem. Phys. 158, 034103 (2023)] demonstrated that excess entropy scaling holds for both fine-grained and corresponding coarse-grained (CG) systems. Despite its universality, a more exact determination of…

化学物理 · 物理学 2023-01-18 Jaehyeok Jin , Kenneth S. Schweizer , Gregory A. Voth

Numerical schemes for wave-like systems with small dissipation are often inaccurate and unstable due to truncation errors and numerical roundoff errors. Hence, numerical simulations of wave-like systems lacking proper handling of these…

数值分析 · 数学 2022-07-27 J. Divahar , A. J. Roberts , Trent W. Mattner , J. E. Bunder , Ioannis G. Kevrekidis

This paper deals with the state estimation of stochastic models with continuous dynamics. The aim is to incorporate spectral differentiation methods into the solution to the Fokker-Planck equation in grid-based state estimation routine,…

信号处理 · 电气工程与系统科学 2025-01-20 Jakub Matousek , Jindrich Dunik , Marek Brandner

We investigate the influence of convection on the formation of molecular spectral lines in the atmospheres of late-type giants. For this purpose we use the 3D hydrodynamical CO5BOLD and classical 1D LHD stellar atmosphere codes and…

太阳与恒星天体物理 · 物理学 2011-05-02 A. Ivanauskas , A. Kucinskas , H. -G. Ludwig , E. Caffau

In Schaerer et al. (1995, Paper I) we have presented the first "combined stellar structure and atmosphere models" (CoStar) for massive stars, which consistently treat the entire mass loosing star from the center out to the outer region of…

天体物理学 · 物理学 2007-05-23 D. Schaerer , A. de Koter , W. Schmutz , A. Maeder

We present the EUV fluxes derived from the recent "combined stellar structure and atmosphere models" (CoStar models). The atmosphere models in particular account for the stellar wind and include non-LTE effects and line blanketing. We…

天体物理学 · 物理学 2007-05-23 D. Schaerer

We present new synthetic broad-band photometric colors for late-type giants based on synthetic spectra calculated with the PHOENIX model atmosphere code. The grid covers effective temperatures T_eff=3000...5000K, gravities log…

天体物理学 · 物理学 2009-11-11 A. Kucinskas , P. H. Hauschildt , H. -G. Ludwig , I. Brott , V. Vansevicius , L. Lindegren , T. Tanabe , F. Allard
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