Self-consistent method to extract non-linearities from pulsating stars light curves I. Combination frequencies.

DOI: 
10.1093/mnras/staa2256
Publication date: 
01/08/2020
Main author: 
Lares-Martiz, M.
IAA authors: 
Lares-Martiz, M.;Garrido, R.;Pascual-Granado, J.
Authors: 
Lares-Martiz, M.;Garrido, R.;Pascual-Granado, J.
Journal: 
Monthly Notices of the Royal Astronomical Society
Refereed: 
Yes
Publication type: 
Article
Pages: 
1194-1204
Abstract: 
Stellar pulsation is a frequent phenomenon among stars which is sustained because of coherent driving mechanisms. When pulsations are driven by heat or convective mechanisms is common to observe combination frequencies in power spectra of their light curves. These combination frequencies are not solutions of the perturbed stellar structure equations. In dense power spectra from a light curve of a given multi-periodic pulsating star, they can compromise the mode identification in an asteroseismic analysis, hence they must be treated as spurious frequencies and conveniently removed. In this paper, a method based on fitting the set of frequencies that best describe a general non-linear model, like the Volterra series, is presented. The method allows to extract these frequencies from the power spectrum, so helping to improve the frequency analysis enabling hidden frequencies to emerge from the initially considered as noise. Moreover, the method yields frequencies with uncertainties several orders of magnitude smaller than the Rayleigh dispersion, sometimes used as if it were an error when identifying combination frequencies. Furthermore, it is compatible with the classical counting cycles method, the so-called O-C method, which is valid only for mono-periodic stars. The method opens the possibility to characterise the non-linear behaviour of a given pulsating star by studying in detail the complex generalised transfer functions in which the model is based on.
Database: 
ADS
SCOPUS
URL: 
https://ui.adsabs.harvard.edu/#abs/2020MNRAS.498.1194L/abstract
ADS Bibcode: 
2020MNRAS.498.1194L
Keywords: 
asteroseismology;stars: oscillations;stars: variables: δ Scuti;Astrophysics - Solar and Stellar Astrophysics