We present a theoretical investigation of the pulsation behaviour of the so-called ``Anomalous" Cepheids (ACs) and its correlation with RR Lyrae stars, Classical and Population II (PII) Cepheids. Using suitable stellar evolution and pulsation models for Z=0.0004, we found that the masses in the range 0.8-1.7 Msun are expected not to cross the instability strip (IS). Stars with mass larger than 1.7 Msun, including both Anomalous and Classical Cepheids, populate with good approximation a common MV-logPF IS, independently of the helium ignition type. At the same time, the less massive pulsators (M <0.8Msun), including RR Lyrae and PII stars, are located in a distinct IS, as a consequence of the different mass-luminosity relations, according to which the pulsation periods increase if the mass of the pulsators decreases.
`Anomalous' or low mass Classical Cepheids?
DEGL'INNOCENTI, SCILLA;
2004-01-01
Abstract
We present a theoretical investigation of the pulsation behaviour of the so-called ``Anomalous" Cepheids (ACs) and its correlation with RR Lyrae stars, Classical and Population II (PII) Cepheids. Using suitable stellar evolution and pulsation models for Z=0.0004, we found that the masses in the range 0.8-1.7 Msun are expected not to cross the instability strip (IS). Stars with mass larger than 1.7 Msun, including both Anomalous and Classical Cepheids, populate with good approximation a common MV-logPF IS, independently of the helium ignition type. At the same time, the less massive pulsators (M <0.8Msun), including RR Lyrae and PII stars, are located in a distinct IS, as a consequence of the different mass-luminosity relations, according to which the pulsation periods increase if the mass of the pulsators decreases.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
