Evidence for nonlinear resonant mode coupling in the Beta Cep star HD 180642 (V1449 Aql) from CoRoT space-based photometry

TL;DR

This study analyzes CoRoT space photometry of the Beta Cep star HD 180642, revealing evidence of nonlinear resonant mode coupling, which enhances understanding of stellar pulsation mechanisms.

Contribution

It provides the first detailed analysis indicating nonlinear resonant mode coupling in HD 180642 using space-based photometry and advanced modeling techniques.

Findings

Best-fit model involves nonlinear resonant frequency and phase locking

Residuals depend on the physical model used for data prewhitening

Results support complex mode interactions in Beta Cep stars

Abstract

We present the CoRoT light curve of the Beta Cep star HD 180642, assembled during the first long run of the space mission, as well as archival single-band photometry. Our goal is to analyse the detailed behaviour present in the light curve and interpret it in terms of excited mode frequencies. After describing the noise properties in detail, we use various time series analysis and fitting techniques to model the CoRoT light curve, for various physical assumptions. We apply statistical goodness-of-fit criteria that allow us to select the most appropriate physical model fit to the data. We conclude that the light curve model based on nonlinear resonant frequency and phase locking provides the best representation of the data. The interpretation of the residuals is dependent on the chosen physical model used to prewhiten the data. Our observational results constitute a fruitful starting point for detailed seismic stellar modelling of this large-amplitude and evolved Beta Cep star.