Asteroseismology of $\beta$ Cephei stars: The stellar inferences tested in hare and hound exercises

TL;DR

This study assesses how observational data quality and mode identification influence the accuracy of asteroseismic inferences on $eta$ Cephei stars, emphasizing the importance of mode identification and model physics in constraining stellar interior processes.

Contribution

It introduces a method extending the forward approach to estimate errors and includes theoretical uncertainties, improving the reliability of seismic modeling of $eta$ Cephei stars.

Findings

Four to five oscillation frequencies with mode identification yield accurate stellar parameters.

Without mode identification, classical constraints can still enable successful seismic modeling.

Constraints on internal structure are valid across different physics if expressed in acoustic variables.

Abstract

The $\beta$ Cephei pulsators are massive main-sequence stars, presenting low radial-order modes. These modes probe in particular the chemical gradient at the edge of the convective core. They hence give constraints on macroscopic processes, such as hydrodynamic or magnetic instabilities. Yet, it is not clear to what extent the seismic inferences depend on the physics employed for the stellar modelling or on the observational dataset. We investigate the observational constraints which are necessary to provide accurate constraints on the mixing processes in $\beta$ Cephei stars. We explore the importance of the identification of the angular degree of modes. Depending on the quality of the seismic dataset and the classical constraints, we estimate the precision achievable with asteroseismology. We propose a method extending the forward approach classically used to model $\beta$ Cephei stars The probability distributions of the asteroseismic-derived stellar parameters are obtained. With these distributions, we provide a systemic way to estimate the errors of the modelling. A particular effort is made to also include the theoretical uncertainties of the models. We then estimate the accuracy and precision of asteroseismology for $\beta$ Cephei stars in a series of hare and hound exercises. The exercises show that a set of four to five oscillation frequencies with an identified angular degree already leads to accurate inferences on the stellar parameters. Without the identification of the modes, the addition of other classical observational constraints allow to succeed the seismic modelling. When the micro-physics of the star and stellar models used for the modelling differ, the constraints derived on the internal structure remain valid if expressed in terms of acoustic variables. The characterisation of the mixing processes at the boundary of the convective core remain model-dependent.