Effects of Metallicity on Mode Switching in Cepheids

The mode switching in Cepheids is studied using the methods of nonlinear theory stellar pulsation, depending on main sequence mass $$M_{0}$$ and abundance elements heavier than helium $$Z$$ . grid evolutionary hydrodynamic models core–helium burning represented by 30 sequences stars with initial masses $$5.7M_{\odot}\leq M_{0}\leq 7.2M_{\odot}$$ $$Z=0.014$$ , 0.018, 0.022. For considered values periods fundamental first overtone at oscillation are shown to depend mean density matter. upper limit period decreases increasing from $${\approx}6.9$$ days for $${\approx}4.1$$ $$Z=0.022$$ theoretical period–radius relation independent agrees well (within 2.5 $$\%$$ ) recent measurements Cepheid radii based Baade–Wesselink method. parameters short–period CG Cas were derived application observational estimates rate change. This star be first–overtone pulsator.