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We present a new method for estimating the H2 cooling rate in the optically thick regime in simulations of primordial star formation. Our new approach is based on the TreeCol algorithm, which projects matter distributions onto a spherical…

Solar and Stellar Astrophysics · Physics 2015-05-05 Tilman Hartwig , Paul C. Clark , Simon C. O. Glover , Ralf S. Klessen , Mei Sasaki

Let $A$ be a square complex matrix; $z_1$, ..., $z_{N}\in\mathbb C$ be arbitrary (possibly repetitive) points of interpolation; $f$ be an analytic function defined on a neighborhood of the convex hull of the union of the spectrum…

Numerical Analysis · Mathematics 2021-08-05 M. Ferus , V. G. Kurbatov , I. V. Kurbatova

Local-box hydrodynamical model atmospheres provide statistical information about the spatial dependence, as well as temporal evolution, of a star's emergent radiation field. Here, we consider late-type stellar atmospheres for which temporal…

Astrophysics · Physics 2009-11-11 Hans-G. Ludwig

We present a new approach for simulating the atmospheric dynamics of the close-in giant planet HD209458b that allows for the decoupling of radiative and thermal energies, direct stellar heating of the interior, and the solution of the full…

Earth and Planetary Astrophysics · Physics 2015-05-14 Ian Dobbs-Dixon , Andrew Cumming , D. N. C Lin

We describe a technique for deriving effective temperatures, surface gravities, rotation velocities, and radial velocities from high resolution near-IR spectra. The technique matches the observed near-IR spectra to spectra synthesized from…

Astrophysics · Physics 2009-11-10 G. W. Doppmann , D. T. Jaffe

The relativistic extension of the classic stellar structure equations is investigated. It is pointed out that the Tolman-Oppenheimer-Volkov (TOV) equation with the gradient equation for local gravitational mass can be made complete as a…

General Relativity and Quantum Cosmology · Physics 2023-08-22 Shuichi Yokoyama

Some of the rapidly oscillating (CP2) stars, have frequencies which are larger than the theoretical acoustic cut-off frequency. As the cut-off frequency depends on the T(tau) relation in the atmosphere, we have computed models and adiabatic…

Astrophysics · Physics 2007-05-23 N. Audard , F. Kupka , P. Morel , J. Provost , W. W. Weiss

Stellar XUV (X-ray and extreme ultraviolet) emission drives the heating and chemical reactions in planetary atmospheres and protoplanetary disks, and therefore, a proper estimation of a stellar XUV spectrum is required for their studies.…

Solar and Stellar Astrophysics · Physics 2024-11-13 Munehito Shoda , Kosuke Namekata , Shinsuke Takasao

Stellar UV spectra are fundamental diagnostics of physical and magnetic properties of stars. For instance, lines like Mg II at 280 nm serve as valuable indicators of stellar activity, providing insights into the activity levels of Sun-like…

Opacity is an important ingredient of the evolution of stars. The calculation of opacity coefficients is complicated by the fact that the plasma contains partially ionized heavy ions that contribute to opacity dominated by H and He. Up to…

Standard 1D stellar evolution models do not correctly reproduce the structure of the outermost layers of stars with convective envelopes. This has been a long-standing problem in stellar modelling affecting both the predicted evolutionary…

A mayor problem that arises in the computation of stellar atmosphere models is the self consistent determination of the temperature distribution via the constraint of energy conservation. The energy balance includes the gains due to the…

Astrophysics · Physics 2007-11-02 Octavio Cardona , Lucio Crivellari , Eduardo Simonneau

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

We describe a correlation function statistic that quantifies the amount of spatial and kinematic substructure in the stellar halo. We test this statistic using model stellar halo realizations constructed from the Aquarius suite of six…

Astrophysics of Galaxies · Physics 2015-05-20 A. P. Cooper , S. Cole , C. S. Frenk , A. Helmi

Observations of the Sun as a star have been key to guiding models of stellar atmospheres and additionally provide useful insights on the effects of granulation and stellar activity on radial velocity measurements. Most high resolution solar…

Instrumentation and Methods for Astrophysics · Physics 2020-03-11 Ashley D. Baker , Cullen H. Blake , Ansgar Reiners

Context. Astrochemical modeling requires, as input, the effective column density of gas (or extinction) that attenuates an external, isotropic, far-ultraviolet radiation field. In three-dimensional simulations, this can be calculated…

Astrophysics of Galaxies · Physics 2025-08-20 Brandt A. L. Gaches

The increasing number of spectra gathered by spectroscopic sky surveys and transiting exoplanet follow-up has pushed the community to develop automated tools for atmospheric stellar parameters determination. Here we present a novel approach…

Solar and Stellar Astrophysics · Physics 2017-06-28 Luca Malavolta , Christophe Lovis , Francesco Pepe , Christopher Sneden , Stephane Udry

The CoRoT and Kepler missions provided a wealth of high-quality data for solar-like oscillations. To make the best of such data for seismic inferences, we need theoretical models with precise near-surface structure, which has significant…

Solar and Stellar Astrophysics · Physics 2019-01-16 T. Sonoi , H. -G. Ludwig , M. -A. Dupret , J. Montalbán , R. Samadi , K. Belkacem , E. Caffau , M. -J. Goupil

Convection is the most important physical process that determines the structure of the envelopes of cool stars. It influences the surface radiation flux and the shape of observed spectral line profiles and is responsible for both generating…

Solar and Stellar Astrophysics · Physics 2009-12-03 F. Kupka

Hadronic $\tau$ decays provide a clean laboratory for the precise study of quantum chromodynamics (QCD). Observables based on the spectral functions of hadronic $\tau$ decays can be related to QCD quark-level calculations to determine…

High Energy Physics - Phenomenology · Physics 2008-11-26 Michel Davier , Andreas Hoecker , Zhiqing Zhang