Constraints on opacities from complex asteroseismology of B-type pulsators: the $\beta$ Cephei star $\theta$ Ophiuchi

TL;DR

This study uses complex asteroseismology to constrain stellar opacities by matching pulsational frequencies and nonadiabatic parameters in the B-type star $ heta$ Ophiuchi, favoring OPAL data.

Contribution

It introduces a comprehensive method combining frequency and nonadiabatic parameter fitting to better constrain stellar opacities in B-type pulsators.

Findings

OPAL opacities better match empirical $f$ parameters.

Seismic models reproduce key pulsation modes.

Strong constraints on stellar opacities from combined data.

Abstract

We present results of a {\bf comprehensive} asteroseismic modelling of the $\beta$ Cephei variable $\theta$ Ophiuchi. {\bf We call these studies {\it complex asteroseismology} because our goal is to reproduce both pulsational frequencies as well as corresponding values of a complex, nonadiabatic parameter, $f$, defined by the radiative flux perturbation.} To this end, we apply the method of simultaneous determination of the spherical harmonic degree, $\ell$, of excited pulsational mode and the corresponding nonadiabatic $f$ parameter from combined multicolour photometry and radial velocity data. Using both the OP and OPAL opacity data, we find a family of seismic models which reproduce the radial and dipole centroid mode frequencies, as well as the $f$ parameter associated with the radial mode. Adding the nonadiabatic parameter to seismic modelling of the B-type main sequence pulsators yields very strong constraints on stellar opacities. In particular, only with one source of opacities it is possible to agree the empirical values of $f$ with their theoretical counterparts. Our results for $\theta$ Oph point substantially to preference for the OPAL data.