Seismic models of O and B stars with Kurucz’s opacity data^⋆

Astronomical Institute of the Wroclaw University, ul. Kopernika 11, 51-622 Wroclaw, Poland
e-mail: cugier@astro.uni.wroc.pl

Received: 5 October 2012
Accepted: 14 March 2014

Abstract

Aims. We investigated seismic models of O and B stars calculated with the new Kurucz opacities implemented in the Opacity Project (OP) and Rogers & Iglesias OPAL opacity tables (OPAL).

Methods. We studied the problem using Dziembowski’s computer codes for linear, nonadiabatic, and nonradial oscillations. We considered seismic models of main sequence (MS) stars for different chemical compositions of elements in the mass-range 9 ≤ M ≤ 70 M_⊙.

Results. The new opacity bump at lgT ≈ 5.06 that occurs in Kurucz’s data influences evolutionary tracks mainly for M ≥ 30 M_⊙ and markedly changes the driving zone for pulsations of stars in the whole mass range studied. We obtained no unstable oscillation modes for models corresponding to the abundance parameter Z ≤ 0.013 and only unstable low-frequency g-modes for 0.013 < Z ≤ 0.021.

Conclusions. The opacity bump at lgT ≈ 5.3 should be significantly larger than the opacity bump at lgT ≈ 5.06 to drive pulsations of B stars in low-degree p-modes. Models with an increased OPAL (or OP) opacity bump at lgT ≈ 5.3 by a factor of about 1.7 have sufficiently large driving zones to excite modes in the β Cephei frequency-domain for 0.003 ≤ Z ≤ 0.021. These values of Z are in a good agreement with those derived spectroscopically for stars in the Galaxy and Magellanic Clouds.