Note on the Ca II Emission in Cepheids

Abstract

It has been shown by O.Wilson and V. Bappu that a strong correlation exists between the absolute magnitude of late type stars and the strength of their Call emissions. We have felt that this relation could also hold for Cepheid variables. from our plate material of Cepheids, taken with the 60" reflector of the Bosque Alegre station of the Cordoba Observatory (dispersion 42 A/mm) we have selected all plates showing double emission in the H and/or K lines. The position of each emission wing was measured, and the difference between both measurements (in Km/sec) was taken as the width "W" of the emission. It is well known that the emission features in Cepheids are usually stronger in the H than in the K line; for this reason the results are based on the emissions in H alone.