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Evolved cool stars of various masses are major cosmic engines, delivering substantial mechanical and radiative feedback to the interstellar medium through strong stellar winds and supernova ejecta. These stars play a pivotal role in…

Solar and Stellar Astrophysics · Physics 2024-02-02 Andrea Chiavassa , Kateryna Kravchenko , Jared A. Goldberg

Studies of the isotopic composition of magnesium in cool stars have so far relied upon the use of one-dimensional (1D) model atmospheres. Since the isotopic ratios derived are based on asymmetries of optical MgH lines, it is important to…

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

Understanding convection in red supergiants and the mechanisms that trigger the mass loss from these evolved stars are the general goals of most observations of Betelgeuse and its inner circumstellar environment. Linear spectropolarimetry…

Solar and Stellar Astrophysics · Physics 2022-05-11 A. López Ariste , S. Georgiev , Ph. Mathias , A. Lèbre , M. Wavasseur , E. Josselin , R. Konstantinova-Antova , Th. Roudier

Understanding the physical process responsible for the transport of energy in the core of $\alpha$ Centauri A is of the utmost importance if this star is to be used in the calibration of stellar model physics. Adoption of different parallax…

Solar and Stellar Astrophysics · Physics 2018-06-06 B. Nsamba , M. J. P. F. G. Monteiro , T. L. Campante , M. S. Cunha , S. G. Sousa

I present here the main results of recent realistic, 3D, hydrodynamical simulations of convection at the surface of metal-poor red giant stars. I discuss the application of these convection simulations as time-dependent, 3D, hydrodynamical…

Astrophysics · Physics 2009-11-13 R. Collet

3D model atmospheres for giants, dwarfs, and white dwarfs, computed with the CO5BOLD code and part of the CIFIST grid, have been used for spectroscopic and asteroseismic studies. Unlike existing plane-parallel 1D structures, these…

Solar and Stellar Astrophysics · Physics 2015-06-16 P. -E. Tremblay , H. -G. Ludwig , B. Freytag , M. Steffen , E. Caffau

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…

Solar and Stellar Astrophysics · Physics 2011-12-13 A. Chiavassa , L. Bigot , F. Thevenin , R. Collet , G. Jasniewicz , Z. Magic , M. Asplund

Non-local, time-dependent convection models have been used to explain the location of double-mode pulsations in Cepheids in the HR diagram as well as the existence and location of the red edge of the instability strip. These properties are…

Solar and Stellar Astrophysics · Physics 2015-04-14 Eva Mundprecht , Herbert J. Muthsam , Friedrich Kupka

Modeling stellar atmospheres is a complex, intriguing task in modern astronomy. A systematic comparison of models with multi-technique observations is the only efficient way to constrain them. Aims: We performed a self-consistent modeling…

Solar and Stellar Astrophysics · Physics 2017-04-12 Gioia Rau , Josef Hron , Claudia Paladini , Benard Aringer , Kjell Eriksson , Paola Marigo , Walter Nowotny , Rebekka Grellmann

Context: The effective temperature is a key parameter governing the properties of a star. For stellar chemistry, it has the strongest impact on the accuracy of the abundances derived. Since Cepheids are pulsating stars, determining their…

Solar and Stellar Astrophysics · Physics 2020-09-16 B. Lemasle , M. Hanke , J. Storm , G. Bono , E. K. Grebel

Model fitting is frequently used to determine the shape of galaxies and the point spread function, for examples, in weak lensing analyses or morphology studies aiming at probing the evolution of galaxies. However, the number of parameters…

Cosmology and Nongalactic Astrophysics · Physics 2012-10-03 Guoliang Li , Bo Xin , Wei Cui

The physical parameters of the retired A star HD 185351 were analysed in great detail by Johnson et al. (2014) using interferometry, spectroscopy and asteroseismology. Results from all independent methods are consistent with HD 185351…

The outer envelopes of massive ($M\gtrsim10\,M_{\odot}$) stars exhibit large increases in opacities from forests of lines and ionization transitions (particularly from iron and helium) that trigger near-surface convection zones.…

Solar and Stellar Astrophysics · Physics 2023-07-19 William Schultz , Lars Bildsten , Yan-Fei Jiang

The phenomenological models of convection use characteristic length scales they do not determine but that are chosen to fit solar or stellar observations. We investigate if changes of these length scales are required between the Sun and low…

Solar and Stellar Astrophysics · Physics 2015-05-20 L. Piau , P. Kervella , S. Dib , P. Hauschildt

Large spectroscopic surveys of the Milky Way need to be calibrated against a sample of benchmark stars to ensure the reliable determination of atmospheric parameters. We present new fundamental stellar parameters of seven giant and subgiant…

Solar and Stellar Astrophysics · Physics 2022-02-09 I. Karovicova , T. R. White , T. Nordlander , L. Casagrande , M. Ireland , D. Huber

(Abridged) We describe the results of three-dimensional (3D) numerical simulations designed to study turbulent convection in the stellar interiors, and compare them to stellar mixing-length theory (MLT). Simulations in 2D are significantly…

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

One of the very first steps astronomers working in stellar physics perform to advance in their studies, is to determine the most common/relevant physical parameters of the objects of study (effective temperature, bolometric luminosity,…

Solar and Stellar Astrophysics · Physics 2014-07-03 A. Bayo , C. Rodrigo , D. Barrado , F. Allard

We introduce a new methodology for the direct extraction of galaxy physical parameters from multi-wavelength photometry and spectroscopy. We use semi-analytic models that describe galaxy evolution in the context of large scale cosmological…

Astrophysics of Galaxies · Physics 2017-06-21 D. Christopher Martin , Thiago Goncalves , Behnam Darvish , Mark Seibert , David Schiminovich

We present first realistic numerical simulations of 3D radiative convection in the surface layers of main sequence A-type stars with Teff = 8000 K and 8500 K, log g = 4.4 and 4.0, recently performed with the CO5BOLD radiation hydrodynamics…

Astrophysics · Physics 2007-05-23 M. Steffen , B. Freytag , H. -G. Ludwig