Updated pulsation models for anomalous Cepheids

Abstract

A theoretical investigation of the pulsation behavior of so-named “anomalous” Cepheids is presented. The study is based on nonlinear convective pulsation models with $Z=0.0001$ and 0.0004, mass in the range 1.3-2.2 $M_{\odot}$ and various luminosity levels. Based on these computations, we derive periods, bolometric light curves and the edges of the instability strip, showing that a variation of the metal abundance from $Z=0.0001$ to 0.0004 has quite small effects on these quantities. Then, using bolometric corrections and color-temperature transformations, we are able to provide the predicted relations connecting pulsational properties (periods, amplitudes) with magnitudes and colors in the various photometric bands. The theoretical pulsational scenario is compared to observed anomalous Cepheids in dwarf spheroidal galaxies and, in particular, the predicted mass-dependent Period-Magnitude-Amplitude and Period-Magnitude-Color relations are used to estimate individual mass values, as well as to discriminate between fundamental (F) and first-overtone (FO) pulsators.