On the crossing mode of the long-period Cepheid SV Vulpeculae

The Cepheid SV Vul is demonstrated to be in the second crossing of the instability strip on the basis of its well-defined period decrease of -214.3 ± 5.5 s yr-1. Recent arguments from its atmospheric abundance pattern that it is in the first crossing are not supported by the historical photometric data. Furthermore, an examination of atmospheric abundance patterns for other Cepheids in advanced strip crossing modes suggests that the presence of CNO-processed material in the atmospheres of intermediate-mass stars does not arise from red supergiant dredge-up phases but from meridional mixing during previous evolution as rapidly-rotating main-sequence B-type stars.