SV Vulpeculae: A first crossing Cepheid?

We have undertaken a search for Cepheid variables which are crossing the instability strip for the first time. Such stars have finished their main sequence evolution and are moving through the HR diagram toward the red giant region. This evolutionary time interval is quite short when compared with the following stages of the core helium burning. Therefore, the number of the Cepheids which are crossing the instability strip for the first time should be at most several percent of the total number of Cepheids. The signature of a first crossing Cepheid is that its surface abundances should reflect its original composition. Using high quality spectral material obtained for a significant number of the Cepheids and determining consistent abundances throughout the sample, we have discovered one star, SV Vul, which can be considered a first crossing Cepheid.