In search of the s-process in cool supergiants: a vital role for laboratory astrophysics

Abstract

We report on progress in determining the chemical composition of the photospheres of massive, cool supergiant stars for the purpose of investigating whether by-products from recent slow neutron capture nucleosynthesis have been transported up to the photosphere by convective processes. Our initial work has been focused on identifying atomic transitions that are useful for stellar abundance work at near-infrared wavelengths and in gathering accurate atomic data for these transitions. The latter task includes the determination of experimental oscillator strengths, which represents a vital role for laboratory astrophysics. We use high-resolution optical and near-infrared spectra of the massive, cool star α. Orionis as the prototype for our study for line identification and synthetic spectrum modeling. Abundances have been determined for a number of heavy elements, and our early results illuminate the problems with atomic data that must be overcome before we are able to derive chemical abundances with the accuracy required for meaningful comparison with calculations for s-process nucleosynthesis.