Light element opacities of astrophysical interest from ATOMIC

We present new calculations of local-thermodynamic-equilibrium (LTE) light element opacities from the Los Alamos ATOMIC code [1] for systems of astrophysical interest. ATOMIC is a multi-purpose code that can generate LTE or non-LTE quantities of interest at various levels of approximation. Our calculations, which include fine-structure detail, represent a systematic improvement over previous Los Alamos opacity calculations using the LEDCOP legacy code [2]. The ATOMIC code uses ab-initio atomic structure data computed from the CATS code, which is based on Cowan's atomic structure codes [3], and photoionization cross section data computed from the Los Alamos ionization code GIPPER [4]. ATOMIC also incorporates a new equation-of-state (EOS) model based on the chemical picture [5]. ATOMIC incorporates some physics packages from LEDCOP and also includes additional physical processes, such as improved free-free cross sections and additional scattering mechanisms. Our new calculations are made for elements of astrophysical interest and for a wide range of temperatures and densities.