Abstract:
Analysis of the RV Tauri star IW Carinae shows a photospheric composition unlike that reported previously for a few other RV Tau stars but resembling that of certain post-asymptotic giant branch stars (post-AGB) stars. IW Car is carbon-rich: several lines of C I are detected and suggest C/O greater than or = 1. The star is generally metal poor. The composition of (Fe/H) approximately -1.0, (Ca/H) approximately = -1.9 but (Zn/H) approximately 0.0 reflects that of gas of solar metallicity from which easily condensable elements have condensed into dust grains and been removed from the star's photosphere. Separation of gas and dust may have occurred in the present or recent stellar wind of IW Car. These characteristics also suggest that RV Tauri stars are post-AGB objects.
