2D computations of g modes

TL;DR

This paper presents comprehensive 2D calculations of gravity modes in rotating stellar models, analyzing their spectral properties, validity of perturbative methods, and identifying new mode types called 'rosette' modes.

Contribution

It introduces detailed 2D computations of g modes in rotating stars and explores the emergence of 'rosette' modes, expanding understanding of stellar oscillation spectra.

Findings

Quantitative validation of perturbative methods up to 70% of break-up velocity.

Identification of 'rosette' modes with unique spatial structures.

Demonstration of the spectrum's regularities and their evolution with rotation.

Abstract

We present complete 2D computations of g modes in distorted polytropic models of stars performed with the Two-dimensional Oscillation Program (TOP). We computed low-degree modes (l=1 modes with radial order n=-1...-14, and l=2,3 modes with n=-1...-5 and -16...-20) of a nonrotating model and followed them by slowly increasing the rotation rate up to 70 % of the Keplerian break-up velocity. We use these computations to determine the domain of validity of perturbative methods up to the 3rd order. We study the evolution of the regularities of the spectrum and show quantitative agreement with the traditional approximation for not too large values of the ratio of the rotation rate to the pulsation frequency. We also show the appearance of new types of modes, called "rosette" modes due to their spatial structure. Thanks to the ray theory for gravito-inertial waves that we developed, we can associate these modes with stable periodic rays.