# Seismic modelling of early B-type pulsators observed by BRITE: I. $\theta$ Ophiuchi

## TL;DR

This study analyzes BRITE-Constellation data of the star θ Ophiuchi, confirming known frequencies, discovering new ones including g modes, and performing seismic modeling to infer internal stellar structure and physical parameters.

## Contribution

It provides the first detailed seismic analysis of θ Ophiuchi, revealing g modes and constraining stellar parameters with improved opacity models and rotation considerations.

## Key findings

- Seven known frequencies confirmed.
- Nineteen new frequency peaks detected.
- Identification of high-order g modes and constraints on stellar parameters.

## Abstract

We analyse time-series observations from the BRITE-Constellation of the well known $\beta$ Cephei type star $\theta$ Ophiuchi. Seven previously known frequencies were confirmed and nineteen new frequency peaks were detected. In particular, high-order g modes, typical for the SPB (Slowly Pulsating B-type star) pulsators, are uncovered. These low-frequency modes are also obtained from the 7-year SMEI light curve. If g modes are associated with the primary component of $\theta$ Oph, then our discovery allows, as in the case of other hybrid pulsators, to infer more comprehensive information on the internal structure. To this aim we perform in-depth seismic studies involving simultaneous fitting of mode frequencies, reproducing mode instability and adjusting the relative amplitude of the bolometric flux variations. To explain the mode instability in the observed frequency range a significant increase of the mean opacity in the vicinity of the $Z$-bump is needed. Moreover, constraints on mass, overshooting from the convective core and rotation are derived. If the low-frequency modes come from the speckle B5 companion then taking into account the effects of rotation is enough to explain the pulsational mode instability.