Radial velocity study of the roAp star HR 1217

Abstract

We analyse 1160 high-dispersion echelle spectra of the roAp star HR 1217 obtained over two 2-week runs. Radial velocities were obtained by cross-correlating with three different templates: a spectrum of a normal star, a spectrum of HR 1217 itself and a spectrum containing only lines of rare-earth elements. We show that rotational modulation is present in the radial velocities calculated using the normal star template and the rare-earth template, but with opposite phases. The roAp pulsations are not detected in the radial velocities from the normal star template, are weakly present in the radial velocities using a template of the star itself and are of large amplitude in the radial velocities obtained using a template containing only rare-earth lines. The pulsation frequencies are, as far as we can tell, identical to those obtained photometrically, although only the mode of largest amplitude is detected independently. These observations confirm that the pulsations in roAp stars are strongly concentrated at the magnetic poles, which is also the location where the rare-earth elements are overabundant. A strong core-wing anomaly is present in the Ha profile of the star.