KY EPSCoR: Stellar Parameter Determinations for Spectral Type A-stars using Spectral Energy Distribution Information

This Kentucky Space Grant (RIA) proposal requests funds to develop a Bayesian, stellar parameter determination procedure for A-stars, using spectral energy distributions (SED) that cover a wavelength range from the far ultraviolet to micron wavelengths. We will make use of all available flux observations from GALEX, 2MASS, WISE and Planck as well as optical photometry, and when available, optical spectroscopy. Our goal is to use blue horizontal branch, blue straggler and normal main-sequence A-star, stellar parameter standards, to constrain ATLAS9, newODF, SEDs across a wide range of temperatures, surface gravities and metallicities. For our calibration sample, we will obtain flux calibrated optical spectroscopy of several dozen A-stars in the magnitude range of 11 < V < 14. When the calibration is complete we will use the Bayesian analysis on A-stars from various surveys (e.g. HK survey, SDSS) making use of all available flux data for a given star. The marginalized probabilities will allow us to characterize the constraint for each stellar parameter, depending on available flux data for that star. This procedure is powerful, because as additional flux data becomes available for a given star, the parameter constraints will tighten. We expect significant improvements to luminosity classification, distances and interstellar extinction using this technique. We will also identify chemically peculiar stars that have suffered photospheric diffusion through the suppressed UV flux (Fe line-blanketing) and increased IR flux (flux redistribution). A subsample of young BS stars is expected to show an upturn in the far UV flux, associated with a hot white dwarf companion. The young BS will reveal important properties of binary mass- transfer, such as spin-up, spin-down, and photospheric abundance anomalies associated with s- process nucleosynthesis in the progenitor AGB star. Using the same procedure, we will also initiate work on empirical SEDs to identify young pre-main sequence stars.