A high resolution spectroscopic survey of the roAp stars

Abstract

We have begun a general high resolution spectroscopic survey of the entire class of roAp stars to study systematics of the pulsations for the class, and to make detailed studies of individual stars. We have high spectral resolution (R ~ 110 000), high time resolution VLT UVES data for 16 of the 35 known members of the class, two of which were discovered during this survey. We show here some examples of studies of pulsation amplitude and phase as a function of line depth in Hα and in the 6145 Å line of Nd iii. The two of these lines together give a nearly continuous map of pulsation amplitude and phase as a function of optical depth from about -5 ≤ log τ₅₀₀₀ ≤ -2, or even higher. Our results for these lines and those of Fe support studies showing settling of Fe and levitation of Nd. The pulsation behaviour provides an independent constraint on atmospheric structure and abundance distribution in roAp stars, hence is important in tests of radiative diffusion calculations.