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Linear damping rates of radial oscillation modes in selected $Kepler$ stars are estimated with the help of a nonadiabatic stability analysis. The convective fluxes are obtained from a nonlocal, time-dependent convection model. The…

Solar and Stellar Astrophysics · Physics 2017-11-08 Günter Houdek

Convection and turbulence in stellar atmospheres have a significant effect on the emergent flux from late-type stars. The theoretical advancements in convection modelling over recent years have proved challenging for the observers to obtain…

Astrophysics · Physics 2015-06-24 Barry Smalley

We present a database of 45,000 atmospheric models (which will become 80,000 models by the end of the project) with stellar masses between 9 and 120 M$_{\odot}$, covering the region of the OB main sequence and W-R stars in the H-R diagram.…

Very massive stars (VMS) dominate the light of young stellar populations and are sources of intense stellar feedback. Their evolution is mainly driven by strong wind mass loss, yet current evolution models make simplistic assumptions on…

Condensable species are crucial in shaping planetary climate. A wide range of planetary climate systems involve understanding non-dilute condensable substances and their influence on climate dynamics. There has been progress on large-scale…

Earth and Planetary Astrophysics · Physics 2021-12-22 Xianyu Tan , Maxence Lefevre , Raymond Pierrehumbert

Hydrogen Balmer lines are commonly used as spectroscopic effective temperature diagnostics of late-type stars. However, the absolute accuracy of classical methods that are based on one-dimensional (1D) hydrostatic model atmospheres and…

Solar and Stellar Astrophysics · Physics 2018-08-03 A. M. Amarsi , T. Nordlander , P. S. Barklem , M. Asplund , R. Collet , K. Lind

Galaxy observations are influenced by many physical parameters: stellar masses, star formation rates (SFRs), star formation histories (SFHs), metallicities, dust, black hole activity, and more. As a result, inferring accurate physical…

MAx is a new tool to estimate parameters from stellar spectra. It is based on the maximum likelihood method, with the likelihood compressed in a way that the information stored in the spectral fluxes is conserved. The compressed data are…

Astrophysics of Galaxies · Physics 2015-05-14 Paula Jofré , Ben Panter , Camilla Juul Hansen , Achim Weiss

Accurate characterization of filamentary structures in star-forming clouds is essential for understanding star formation. Traditional methods fit observed surface density profiles $\Sigma(r)$ with slope $\gamma$ and width $H$ using the…

Astrophysics of Galaxies · Physics 2026-05-15 Alexander Men'shchikov , Guo-Yin Zhang

The last decade has seen a rapid development in asteroseismology thanks to the CoRoT and Kepler missions. With more detailed asteroseismic observations available, it is becoming possible to infer exactly how oscillations are driven and…

Solar and Stellar Astrophysics · Physics 2020-06-03 Yixiao Zhou , Martin Asplund , Remo Collet , Meridith Joyce

We investigate the relation between 1D atmosphere models that rely on the mixing length theory and models based on full 3D radiative hydrodynamic (RHD) calculations to describe convection in the envelopes of late-type stars. The adiabatic…

Solar and Stellar Astrophysics · Physics 2014-12-24 Zazralt Magic , Achim Weiss , Martin Asplund

Cool giant and supergiant star atmospheres are characterized by complex velocity fields originating from convection and pulsation processes which are not fully understood yet. The velocity fields impact the formation of spectral lines,…

Solar and Stellar Astrophysics · Physics 2018-02-21 K. Kravchenko , S. Van Eck , A. Chiavassa , A. Jorissen , B. Freytag , B. Plez

BA-type supergiants show a high potential as versatile indicators for modern astronomy. The focus here is on the determination of accurate and precise atmospheric parameters for a sample of 35 Galactic BA-type supergiants. Some first…

Solar and Stellar Astrophysics · Physics 2012-07-03 M. Firnstein , N. Przybilla

Nonlinear pulsation modeling of classical variable stars is among the first topics which were developed at the beginning of the computational era. Various developments were made, and many questions were answered in the past 60 years, and…

Solar and Stellar Astrophysics · Physics 2023-09-14 Gábor B. Kovács , János Nuspl , Róbert Szabó

We present new calibrations of stellar parameters of O stars at solar metallicity taking non-LTE, wind, and line-blanketing effects into account. Gravities and absolute visual magnitudes are derived from results of recent spectroscopic…

Astrophysics · Physics 2009-05-29 F. Martins , D. Schaerer , D. J. Hillier

In the surface layers of late-type stars, stellar convection is manifested with its typical granulation pattern due to the presence of convective motions. The resulting photospheric up- and downflows leave imprints in the observed spectral…

Solar and Stellar Astrophysics · Physics 2014-05-30 Zazralt Magic , Martin Asplund

We describe a self-consistent spectrum analysis technique employing non-LTE line formation, which allows precise atmospheric parameters of massive stars to be derived: 1sigma-uncertainties as low as ~1% in effective temperature and…

Solar and Stellar Astrophysics · Physics 2015-03-17 Maria-Fernanda Nieva , Norbert Przybilla

The computationally demanding nature of radiative-hydrodynamical simulations of stellar surface convection warrants an investigation of the sensitivity of the convective structure and spectral synthesis to the numerical resolution and…

Astrophysics · Physics 2007-05-23 M. Asplund , H. -G. Ludwig , AA. Nordlund , R. F. Stein

State-of-the-art one-dimensional (1D) stellar evolution codes rely on simplifying assumptions, such as mixing length theory, in order to describe superadiabatic convection. As a result, 1D stellar structure models do not correctly recover…

Solar and Stellar Astrophysics · Physics 2019-08-07 Andreas Christ Sølvsten Jørgensen , Achim Weiss