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Description
We provide low temperature opacity data that incorporate varied abundances of the elements carbon and nitrogen. In the temperature range that we focus at, molecules are the dominant opacity source. Our dataset spans a large metallicity range and shall deliver the necessary input data for stellar evolution models as well as other applications. We conduct chemical equilibrium calculations in order to evaluate the partial pressures of neutral atoms, ions and molecules. Based on a large dataset containing atomic line and continuum data, and, most importantly, a plethora of molecular lines, we subsequently calculate Rosseland mean opacity coefficients. This is done not only for a number of different metallicities, but also for varied abundances of the isotopes ^12^C and ^14^N at each metallicity. The molecular data comprise the main opacity sources at either an oxygen-rich or carbon-rich chemistry. We tabulate the opacity coefficients as a function of temperature and, basically, density. Already within a certain chemistry regime an alteration in the carbon abundance causes, due to the special role of the CO molecule, considerable changes in the Rosseland opacity. The transition from a scaled solar (i.e. oxygen-rich) mixture to the carbon-rich regime results in opacities that can, at low temperatures, be orders of magnitude different compared to the initial situation. The reason is that different molecular absorbers make up the mean opacity in either case. A varying abundance of nitrogen has less pronounced effects but, nevertheless, cannot be neglected.
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