A Re-examination of Stellar Opacities and Implications for Solar Models

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AST-0907763PradhanThis award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).Stellar opacity is the fundamental quantity in stellar models. In recent years an inexplicable solar abundances anomaly has emerged, between light element abundances derived spectroscopically and from the most sophisticated atmospheres models, on the one hand, and interior models consistent with extremely accurate helioseismological observations, on the other hand. An increase in opacity of 10-20% could perhaps reconcile the currently divergent models, and the primary aim of this project is to investigate the accuracy of the models and test this suggestion, focusing on a detailed quantitative re-assessment of opacities. The work entails more accurate and extensive atomic calculations, including relativistic effects, an improved equation of state in the "chemical picture", and high-resolution computation of monochromatic and mean opacities, and radiative accelerations. The new opacities codes will be interfaced with an electronic data server for efficient distribution.The calculation of opacities and radiative accelerations is a symbiotic exercise in atomic physics, plasma physics, and astrophysics. Although the results will be generally useful in many stellar studies, the impact will be much wider. Large-scale high-accuracy atomic data are useful in spectral analysis of nebulae, active galactic nuclei, supernovae, and other astronomical objects, and also very helpful in nuclear fusion plasma diagnostics, laser-atom interactions, and photoionization studies on synchrotron based light sources. Even more generally, these advanced methods in atomic physics cover important science from atmospheric research to energy technology.