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The building of a stellar structure requires knowing the Rosseland mean opacity at each layer of the model. This mean opacity is very often interpolated in pre-computed tables due to the overwhelming time to compute it from monochromatic…

Solar and Stellar Astrophysics · Physics 2021-02-10 Alain Hui-Bon-Hoa

The high-temperature and high-pressure equations of states (EOSs) of rhenium up to 3000 K and 900 GPa are predicted by a recently developed method in the framework of statistical ensemble theory with \textit{ab initio} computational…

Materials Science · Physics 2024-12-09 Yue-Yue Tian , Hui-fen Zhang , Bo-Yuan Ning , Xi-Jing Ning

Rosseland mean opacity plays an important role in theories of stellar evolution and X-ray burst models. In the high-temperature regime, when most of the gas is completely ionized, the opacity is dominated by Compton scattering. Our aim here…

High Energy Astrophysical Phenomena · Physics 2017-02-01 Juri Poutanen

This study introduces a framework that employs Gaussian Processes (GPs) to develop high-fidelity equation of state (EOS) tables, essential for modeling material properties across varying temperatures and pressures. GPs offer a robust…

Materials Science · Physics 2026-04-14 Lin H. Yang , James A. Gaffney

We present newly calculated low-temperature opacities for gas with a primordial chemical composition. In contrast to earlier calculations which took a pure metal-free Hydrogen/Helium mixture, we take into account the small fractions of…

Astrophysics · Physics 2009-11-10 Michael Mayer , Wolfgang J. Duschl

The opacity due to photodissociation of 24MgH is investigated in the atmospheres of cool stars. The lowest two electronic transitions A 2Pi -- X 2Sigma+ and B' 2Sigma+ -- X 2 Sigma+ are considered where the cross sections for the latter…

Astrophysics · Physics 2009-11-07 P. F. Weck , A. Schweitzer , P. C. Stancil , P. H. Hauschildt , K. Kirby

We present a set of 1194 Type-1 Rosseland-mean opacity tables for four different metallicity mixtures. These new Los Alamos OPLIB atomic radiative opacity tables are an order of magnitude larger in number than any previous opacity table…

We present a new, publicly available, set of Los Alamos OPLIB opacity tables for the elements hydrogen through zinc. Our tables are computed using the Los Alamos ATOMIC opacity and plasma modeling code, and make use of atomic structure…

Solar and Stellar Astrophysics · Physics 2016-02-03 J. Colgan , D. P. Kilcrease , N. H. Magee , M. E. Sherrill , J. Abdallah, , P. Hakel , C. J. Fontes , J. A. Guzik , K. A. Mussack

We investigate the Equation of State (EOS) of classical systems having 300 and 512 particles confined in a box with periodic boundary conditions. We show that such a system, independently on the number of particles investigated, has a…

Nuclear Theory · Physics 2009-10-28 P. Finocchiaro , M. Belkacem , T. Kubo , V. Latora , A. Bonasera

Heating of whole interstellar dust grains by cosmic-ray (CR) particles affects the gas-grain chemistry in molecular clouds by promoting molecule desorption, diffusion, and chemical reactions on grain surfaces. The frequency of such heating…

High Energy Astrophysical Phenomena · Physics 2016-07-06 Juris Kalvāns

A new dataset of atomic oxygen and molecular nitrogen number density profiles, along with thermospheric temperature profiles between 180 and 500 km, has been developed. These profiles are derived from solar occultation measurements made by…

A thermodynamically consistent phase-field model is developed to study the non-isothermal grain coalescence during the sintering process, with a potential application to the simulation in unconventional sintering techniques, e.g. spark…

Materials Science · Physics 2018-06-08 Yangyiwei Yang , Min Yi , Bai-Xiang Xu , Long-Qing Chen

The limited availability of accurate experimental data in wide ranges of pressure, temperature, and composition is the main constraining factor for the proper development and assessment of thermodynamic models and equations of state. In the…

We introduce a fast and versatile computer code, GGchem, to determine the chemical composition of gases in thermo-chemical equilibrium down to 100 K, with or without equilibrium condensation. We review the data for molecular equilibrium…

Earth and Planetary Astrophysics · Physics 2018-06-06 P. Woitke , Ch. Helling , G. H. Hunter , J. D. Millard , G. E. Turner , M. Worters , J. Blecic , J. W. Stock

Grain surface chemistry is key to the composition of protoplanetary disks around young stars. The temperature of grains depends on their size. We evaluate the impact of this temperature dependence on the disk chemistry. We model a…

Astrophysics of Galaxies · Physics 2021-10-13 S. Gavino , A. Dutrey , V. Wakelam , S. Guilloteau , J. Kobus , S. Wolf , W. Iqbal , E. Di Folco , E. Chapillon , V. Piétu

Stellar seismology appears more and more as a powerful tool for a better determination of the fundamental properties of solar-type stars. However the particular case of Sun is still challenging. The helioseismic sound speed determination…

We have developed a public code, Optab, that outputs Rosseland, Planck, and two-temperature Planck mean gas opacity tables for radiation hydrodynamics simulations in astrophysics. The code is developed for modern high-performance computing,…

Instrumentation and Methods for Astrophysics · Physics 2022-03-14 Shigenobu Hirose , Peter Hauschildt , Takashi Minoshima , Kengo Tomida , Takayoshi Sano

We present a method to include the evolution of the grain size and grain opacity $\kappa_\mathrm{gr}$ in the equations describing the structure of protoplanetary atmospheres. The key assumption of this method is that a single grain size…

Earth and Planetary Astrophysics · Physics 2015-06-22 Chris W. Ormel

Icy grains in the interstellar medium and star-formation regions consist of a variety of materials. Such composite grains interact differently with cosmic-ray (CR) particles compared to simple single-material grains. We aim to calculate the…

Astrophysics of Galaxies · Physics 2022-09-21 Juris Kalvans , Juris Roberts Kalnin