Physics – Atomic Physics
Scientific paper
Jan 2011
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2011aas...21743603p&link_type=abstract
American Astronomical Society, AAS Meeting #217, #436.03; Bulletin of the American Astronomical Society, Vol. 43, 2011
Physics
Atomic Physics
Scientific paper
New solar abundances (Asplund etal., ARAA, 47, 522, 2009) are widely discordant with the 'standard' abundances. It has been suggested that a marginal, but significant, enahancement in stellar interior opacities might resolve the issue, which otherwise results in discrepancies of up to 50% in light elements such as C, N, O and Ne. We report on theoretical and experimental investigations of stellar interior opacities in general, and the the solar radiative/convection zone boundary in particular. We especially examine the atomic physics employed in existing opacities calculations, such as the Opacity Project and OPAL, and find that fundamental processes may not have been accounted for accurately; to wit: the assumption that autoionizing resonances can be treated as lines. It is well known that inner-shell electronic transitions in complex atomic species, such as Iron, account for most of the opacity. But they generally lie in the bound-free continuum and should be resolved as freqency dependent resonance profiles in photoionization cross sections, rather than considered as bound-bound transitions in opacities calculations. Recent work shows that there may be sufficient and significant uncertainty in current opacities, at least at the level of 10% in Rosseland Mean Opacities, to address if not resolve the solar abundances problem, given the inverse correlation between opacities and abundances.
Simultaneously with our theoretical investigation, there is a major experimental effort to measure monochromatic opaciites for the first time in stellar interior conditions. The inertial confinement fusion Z-pinch facility at the Sandia National Laboratory is now capable of producing plasmas at conditions prevalent at the boundary of the convection zone (BCZ) in the Sun. Preliminary measurements of monochromatic opacity of iron ions, the primary determinant of effective opacity, differ from theoretical models. We present first results from a new high-precision opacities code HIPOP using new atomic parameters.
Bailey James E.
Nahar Sultana N.
Pinsonneault Marc
Pradhan Anil Kumar
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