Updated Low-temperature Gas Opacities with ÆSOPUS 2.0
Paola Marigo, B. Aringer, L. Girardi, A. Bressan
Abstract
Abstract This work introduces new low-temperature gas opacities in the range <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mn>3.2</mml:mn> <mml:mo>≲</mml:mo> <mml:mi>log</mml:mi> <mml:mo stretchy="false">(</mml:mo> <mml:mi>T</mml:mi> <mml:mrow> <mml:mo stretchy="true">/</mml:mo> </mml:mrow> <mml:mi mathvariant="normal">K</mml:mi> <mml:mo stretchy="false">)</mml:mo> <mml:mo>≲</mml:mo> <mml:mn>4.5</mml:mn> </mml:math> computed with the Æ SOPUS code under the assumption of thermodynamic equilibrium. In comparison to the previous version, Æ SOPUS 1.0 , we updated and expanded molecular absorption to include 80 species, mostly using the recommended line lists currently available from the ExoMol and HITRAN databases. Furthermore, in light of a recent study, we revised the H − photodetachment cross section, added the free–free absorption of other negative ions of atoms and molecules, and updated the collision-induced absorption due to H 2 /H 2 , H 2 /H, H 2 /He, and H/He pairs. Using the new input physics, we computed tables of Rosseland mean opacities for several scaled-solar chemical compositions, including Magg et al.'s most recent one, as well as α -enhanced mixtures. The differences in opacity between the new Æ SOPUS 2.0 and the original Æ SOPUS 1.0 versions, as well as other sets of calculations, are discussed. The new opacities are released to the community via a dedicated webpage that includes both precomputed tables for widely used chemical compositions and a web interface for calculating opacities on the fly for any abundance distribution.