On resonant and non-resonant origin of double-mode Cepheid pulsation

TL;DR

This paper investigates the origins of double-mode Cepheid pulsations, highlighting the importance of resonant and non-resonant mechanisms, and correcting previous models by including negative buoyancy effects, which restricts the parameter space for resonant models.

Contribution

It demonstrates that including negative buoyancy effects significantly alters the models, suggesting non-resonant mechanisms are likely responsible for most observed double-mode Cepheids.

Findings

Resonant models are limited to narrow parameters.

Negative buoyancy effects are crucial in modeling.

Non-resonant mechanisms likely explain most double-mode Cepheids.

Abstract

Double-mode Cepheid behaviour may arise either from non-resonant or resonant mode interaction. Inclusion of turbulent convection into pulsation codes by Kollath et al. (1998) led to stable double-mode F+1O Cepheid pulsation. However, our recent computations (Smolec & Moskalik 2008) indicate, that these models resulted from incorrect neglect of negative buoyancy effects. Once these effects are taken into account, only some resonant double-mode models could be found. These models do not solve the puzzle of double-mode phenomenon, as they are restricted to narrow parameter ranges. For majority of the observed double-mode Cepheids non-resonant mechanism has to be operational.