A simple representation of oscillation modes in stars: from mixed modes coupling to glitches

TL;DR

This paper introduces a versatile analytical expression for stellar oscillation modes that accounts for internal structural glitches, enhancing the understanding of their frequency spectra without assuming small perturbations.

Contribution

It presents a general quantization formula for mixed modes in stars that incorporates glitches characterized by three parameters, applicable to diverse stellar structures.

Findings

The expression reduces to previous models when glitches are weak.

It effectively models oscillation modes with internal sharp structural variations.

Applicable to various stellar configurations without perturbation assumptions.

Abstract

Analytical resonance conditions for oscillation modes in stars are very helpful both to predict and to examine their frequency spectra, as well as to make the link with their internal properties. In this short paper, we introduce a general quantization expression for oscillation modes accounting for the possible existence of a local sharp variation in the equilibrium structure, a so-called glitch. This representation is based on a direct adaptation of the progressive-wave picture of mixed modes proposed by Takata (2016b). In this formulation, a glitch turns out to be characterized by three parameters: its acoustic depth, the phase lags introduced after the wave reflection at the considered point, and a coupling factor. Such an expression has two main advantages. First, it can be easily applicable to a lot of different structural configurations. Second, it does not assume that the glitch is a small perturbation. Actually, we check that the obtained expression tends to the formulations previously derived when the glitch is weak. These research notes represent a preliminary step towards a more generalized description of multi-cavity oscillation modes, that was briefly addressed in the poster presented at the PHOST conference.