Modeling the near-ultraviolet band of GK stars. III. dependence on abundance pattern

Abstract

We extend the grid of non-LTE (NLTE) models presented in Paper II to explore variations in abundance pattern in two ways: (1) the adoption of the Asplund et al. (GASS10) abundances, (2) for stars of metallicity, [M/H], of −0.5, the adoption of a non-solar enhancement of [alpha]-elements by +0.3 dex. Moreover, our grid of synthetic spectral energy distributions (SEDs) is interpolated to a finer numerical resolution in both T[subscript eff] ([delta]T[subscript eff] = 25 K) and log g ([delta] log g = 0.25). We compare the values of T[subscript eff] and log g inferred from fitting LTE and NLTE SEDs to observed SEDs throughout the entire visible band, and in an ad hoc “blue” band. We compare our spectrophotometrically derived T[subscript eff] values to a variety of T[subscript eff] calibrations, including more empirical ones, drawn from the literature. For stars of solar metallicity, we find that the adoption of the GASS10 abundances lowers the inferred T[subscript eff] value by 25–50 K for late-type giants, and NLTE models computed with the GASS10 abundances give T[subscript eff] results that are marginally in better agreement with other T[subscript eff] calibrations. For stars of [M/H] = −0.5 there is marginal evidence that adoption of [alpha]-enhancement further lowers the derived T[subscript eff] value by 50 K. Stellar parameters inferred from fitting NLTE models to SEDs are more dependent than LTE models on the wavelength region being fitted, and we find that the effect depends on how heavily line blanketed the fitting region is, whether the fitting region is to the blue of the Wien peak of the star’s SED, or both.