AESOPUS 2.1: Low-Temperature Opacities Extended to High Pressure

We address the critical need for accurate Rosseland mean gas opacities in high-pressure environments, spanning temperatures from 100 K to 32000 K. Current opacity tables from Wichita State University and AESOPUS 2.0 are limited to \(\log(R) \le 1\), where \(R=\rho\, T_6^{-3}\) in units of \(\mathrm{...

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Bibliographic Details
Published inarXiv.org
Main Authors Marigo, Paola, Addari, Francesco, Bossini, Diego, Bressan, Alessandro, Costa, Guglielmo, Girardi, Leo, Trabucchi, Michele, Volpato, Guglielmo
Format Paper
LanguageEnglish
Published Ithaca Cornell University Library, arXiv.org 17.09.2024
Subjects
Astrochemistry
Atmospheric pressure
Brown dwarf stars
Density
Extrasolar planets
High pressure
Ionization potentials
Low mass stars
Low temperature
Opacity
Planetary atmospheres
Pressure broadening
Pressure effects
Stellar evolution
Tables (data)
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Summary:We address the critical need for accurate Rosseland mean gas opacities in high-pressure environments, spanning temperatures from 100 K to 32000 K. Current opacity tables from Wichita State University and AESOPUS 2.0 are limited to \(\log(R) \le 1\), where \(R=\rho\, T_6^{-3}\) in units of \(\mathrm{g}\,\mathrm{cm}^{-3}(10^6\mathrm{K})^{-3}\). This is insufficient for modeling very low-mass stars, brown dwarfs, and planets with atmospheres exhibiting higher densities and pressures (\(\log(R) > 1\)). Leveraging extensive databases such as ExoMol, ExoMolOP, MoLLIST, and HITEMP, we focus on expanding the AESOPUS opacity calculations to cover a broad range of pressure and density conditions (\(-8 \leq \log(R) \leq +6\)). We incorporate the thermal Doppler mechanism and micro-turbulence velocity. Pressure broadening effects on molecular transitions, leading to Lorentzian or Voigt profiles, are explored in the context of atmospheric profiles for exoplanets, brown dwarfs, and low-mass stars. We also delve into the impact of electron degeneracy and non-ideal effects such as ionization potential depression under high-density conditions, emphasizing its notable influence on Rosseland mean opacities at temperatures exceeding \(10,000\) K. As a result, this study expands AESOPUS public web interface for customized gas chemical mixtures, promoting flexibility in opacity calculations based on specific research needs. Additionally, pre-computed opacity tables, inclusive of condensates, are provided. We present a preliminary application to evolutionary models for very low-mass stars.
ISSN:2331-8422