Increased evidence for overtone pulsation in galactic cepheids - SU Cassiopeiae

Abstract

The status and the pulsation mode of the classical cepheid SU Cas are discussed in light of a radius value which has been determined on the basis of a homogeneous and accurate data set and two independent methods. It is hypothesized that (1) the radius within its error limits is not compatible with currently accepted period-radius relations, assuming fundamental mode pulsations, (2) the anomalously large Wesselink radius mass can only be explained if first- or second-order pulsation is assumed, (3) the location of the star in the H-R diagram with respect to the fundamental mode blue edge indicates the likelihood of first overtone pulsation, (4) the relative radius variation and effective temperature show the star to belong to a very small group of cepheids which are probably overtone pulsators, and (5) the peculiar properties of the light curve Fourier components can probably be understood in terms of a nonfundamental mode pulsation.