Study of sdO models: mode trapping

TL;DR

This paper investigates mode trapping phenomena in sdO stellar models, revealing how chemical transitions influence mode behavior without significantly affecting mode driving, and providing insights into the selection effects of trapped modes.

Contribution

First detailed analysis of mode trapping in sdO models, identifying chemical transition effects on mode trapping and their limited impact on mode excitation.

Findings

Mode trapping occurs at He/H and C-O/He transitions.

Trapped modes have lower amplitudes in damping regions.

Mode trapping influences mode selection but not excitation.

Abstract

We present the first description of mode trapping for sdO models. Mode trapping of gravity modes caused by the He/H chemical transition is found for a particular model, providing a selection effect for high radial order trapped modes. Low- and intermediate-radial order {\em p}-modes (mixed modes with a majority of nodes in the P-mode region) are found to be trapped by the C-O/He transition, but with no significant effects on the driving. This region seems to have also a subtle effect on the trapping of low radial order {\em g}-modes (mixed modes with a majority of nodes in the G-mode region), but again with no effect on the driving. We found that for mode trapping to have an influence on the driving of sdO modes (1) the mode should be trapped in a way that the amplitude of the eigenfunctions is lower in a damping region and (2) in this damping region significant energy interchange has to be produced.