Line-Blanketing in Theoretical Model Atmospheres for F, G, and K-Type Stars

Abstract

We have computed improved flux distributions from Gustafsson et al.'s extensive grids of theoretical model atmospheres for late-type (F-K) giant and dwarf stars. In order to enhance the realism of the computed fluxes throughout the optical and the ultraviolet wavelength ranges, the massive list of atomic opacity sources used for the hotter Kurucz models was also employed in calculating the cooler spectra. For both the giant and the dwarf models, the resulting synthetic UBVRI photometry provides excellent matches to the spectroscopic calibrations of the observed metallicity and temperature scales based on the ultraviolet excesses, δ (U-B), and the BVRI colors, respectively. We conclude that atomic line-blanketing due to known, rather than “missing”, opacity sources accounts for the largest fraction of the systematic UV discrepancy existing between observations and earlier model calculations.