2016MNRAS.455L..67M

Recently, Bailey et al. made a direct measurement of the iron opacity at the physical conditions of the solar tachocline. They found that the wavelength-integrated iron opacity is roughly 75 percent higher than what the Opacity Project (OP) and OPAL models predict. Here, we compute new opacity tables with enhanced iron and nickel contributions to the Rosseland mean opacity by 75 percent each, and compute three dense mesa grids of evolutionary models for Galactic O- and B-type stars covering from 2.5 to 25 M_☉ from zero-age main sequence (ZAMS) until Teff = 10000 K after the core hydrogen exhaustion. We carry out non-adiabatic mode stability analysis with gyre, and update the extension of the instability strips of heat-driven p- and g-mode pulsators, and the hybrid slowly pulsating B (SPB) - β Cep stars. We compare the position of two confirmed late O-type β Cep and eight confirmed hybrid B-type pulsators with the new instability domains, and justify that ∼ 75 percent enhancement, only in iron opacity, is sufficient to consistently reproduce the observed position of these stars on the logTeff versus logg plane. We propose that this improvement in opacities be incorporated in the input physics of new stellar models.