OBSERVATIONS OF MAGNETO-ACOUSTIC MODES IN STRONGLY MAGNETIC PULSATING ROAP STARS

摘要

Studies of line profile variations in rapidly oscillating Ap stars provide information about both surface and depth variations of abundances, pulsations modes and magnetic fields. These stars thus provide an opportunity to study the interaction of p modes with strong magnetic fields for comparison with local helioseismic studies of the interaction of p modes with sunspots and other magnetic regions in the Sun. We have obtained high resolution, high signal-to- noise spectroscopic data for most of the 35 known roAp stars with the Ultraviolet and Visual Echelle Spectrograph (UVES) on unit 2 (Kueyen) of the Very Large Telescope. In this paper we illustrate some of the rich variety of behaviour that can be seen as a function of atmospheric depth with line bisector studies for the Hα line and the Nd III 6145 A line in ten roAp stars.