Talk abstract details

Studies based on high-resolution spectroscopic observations of rapidly oscillating Ap (roAp) stars show a surprising diversity in the pulsation behavior derived from different lines in there spectra. In general, this studies show that roAp stars exhibit, in there atmospheric layers, a combination of running and standing waves. Here we present the results of theoretical model with the purpose of understanding the general trends seen in the atmospheric pulsation data acquired with high-resolution spectroscopy. We concentrate in the region of the star where the magnetic pressure is much larger than the gas pressure, the outer atmospheric region, and take the velocity field at the base of this region from the code Magnetic perturbations to pulsations in Ap stars (MAPPA-Cunha(2006)). Starting from the equations for the displacement parallel and perpendicular to the direction of the magnetic field and using the analytical solutions for the velocity components appropriate to the outermost layer, where the atmosphere can be considered isothermal, we determine the expression for the velocity component parallel to the line of sight averaged over the visible stellar disk, for a general position of the observer. Then we derive the wave amplitude and phase as function of height in the atmosphere and compare to the general trends of the phase and amplitude derived from the spectroscopic data. Such comparison allows as to link the observed behavior to the physical and geometric quantities that are involved in the problem.