Toward a New Paradigm in the Analysis of Asteroseismic Lightcurves

Suárez, J. C.; Garrido, R.; Pascual-Granado, J.; Hernández, A. García; Franciscis, Sebastiano de; Lares-Martiz, M.; Rodón, J. R.

doi:10.3389/fspas.2020.00012

Cited by 3 publications

(1 citation statement)

References 51 publications

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“…First of all, we consider spurious peaks as significant and non-significant maxima in the frequency spectrum that do not correspond to any oscillation mode of the pulsating star (Suárez et al 2020). In this sense, peaks associated to non-linear effects should not be considered spurious since they are originated by oscillations themselves.…”

Section: Discussion : Frequencies Inside the Rayleigh Interval And Bi...mentioning

confidence: 99%

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

Lares-Martiz,

Garrido,

Pascual-Granado

2020

Preprint

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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 nonlinear 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, usually taken as the present error in a standard frequency analysis. 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.

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Section: Discussion : Frequencies Inside the Rayleigh Interval And Bi...mentioning

confidence: 99%

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

Lares-Martiz,

Garrido,

Pascual-Granado

2020

Preprint

View full text Add to dashboard Cite

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

Lares-Martiz

Garrido

Pascual-Granado

2020

Monthly Notices of the Royal Astronomical Society

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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.

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Characterizing the features of the low-amplitude peaks in delta Scuti stars with TESS

Barceló Forteza,

Pascual-Granado,

Suárez

et al. 2024

Monthly Notices of the Royal Astronomical Society

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The presence of low-amplitude peaks over the noise in the power spectra of δ Scuti stars is frequently disregarded. These seemingly insignificant peaks, collectively referred to as grass, might contain valuable information about the origin of these stars and the reasons behind the occurrence or absence of a plateau. It is crucial to systematically parameterize the grass phenomenon throughout a comprehensive sample that covers the entire δ Scuti star parameter range. Thus, we conduct a quantitative study of long-duration, high-duty-cycle TESS light curves, leading to improved detection methods for plateaus and a deeper understanding of their nature. This approach minimizes the impact of unresolved peaks caused by mode variations over time. Additionally, we present appropriate analysis techniques to mitigate window effects and identify and eliminate spurious peaks. We demonstrate here that the grass can be effectively parameterized based on peak density. With such parameterization two distinct regimes are found: the sparse grass regime, characterized by low peak density and the absence of a plateau in the power spectra, and the dense grass regime, characterized by high peak densities and the presence of an observable plateau. Our study is the first rigorous quantification of the emergence of such a plateau in the power spectra of δ Scuti stars. Since the grass might be related with fractality, mode variability, and stellar rotation rate, its parameterization opens a new way to analyze these stars.

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Toward a New Paradigm in the Analysis of Asteroseismic Lightcurves

Cited by 3 publications

References 51 publications

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

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

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

Characterizing the features of the low-amplitude peaks in delta Scuti stars with TESS

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