2001MNRAS.327..881D

We carried out a series of linear stability analyses of the radial and low-degree non-radial p modes for stellar models with initial masses of 6-30M_solar. The stellar models were computed by using convective overshoot distance d_over=0.10, 0.25 and 0.40H_P. Our numerical results show that the β Cephei instability strip forms a horn-shaped region pointing upwards near the main sequence on the Hertzsprung-Russell diagram (HRD). The lower part of the instability strip for the radial modes join the zero-age main-sequence (ZAMS) at M∼8.0-10.5M_solar, while the top of the instability strip extends up to M∼15.5M_solar. The instability strip for the non-radial modes is even wider. The overall instability strip is dominated by the radial and non-radial fundamental modes. The first overtone (the radial-order index n=1) is also pulsationally unstable. We have shown that the β Cephei stability is almost independent of the overshoot parameter d_over used for the stellar models, while it depends critically on the metal abundance. With decreasing metal abundance, the instability region shrinks and eventually disappears for Z≲0.005.