J. Pascual-Granado

OBSERVATIONAL Δ ν –

Delta Scuti (δ Sct) stars are intermediate-mass pulsators, whose intrinsic oscillations have been studied for decades. However, modeling their pulsations remains a real theoretical challenge, thereby even hampering the precise determination of global stellar parameters. In this work, we used space photometry observations of eclipsing binaries with a δ Sct component to obtain reliable physical parameters and oscillation frequencies. Using that information, we derived an observational scaling relation between the stellar mean density and a frequency pattern in the oscillation spectrum. This pattern is analogous to the solar-like large separation but in the low order regime. We also show that this relation is independent of the rotation rate. These findings open the possibility of accurately characterizing this type of pulsator and validate the frequency pattern as a new observable for δ Sct stars.

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Using ultra-precise data from space instrumentation, we found that the underlying functions of stellar light curves from some AF pulsating stars are non-analytic, and consequently their Fourier expansion is not guaranteed. This result demonstrates that periodograms do not provide a mathematically consistent estimator of the frequency content for this type of variable stars. More importantly, this constitutes the first counterexample against the current paradigm, which considers that any physical process is described by a continuous (band-limited) function that is infinitely differentiable.

RELATION FOR δ Sct STARS USING ECLIPSING BINARIES AND SPACE PHOTOMETRY

Context. Gaps in time series originate spurious frequencies in the power spectra. In the case of light curves of pulsating stars, t his hampers the identification of the theoretical oscillation m odes. When these gaps are small as compared with the total time span, the usual approach to overcome these diffi culties involves linear interpolation. In any case the resu lting time series has not the property of preserving the original frequency content of the pulsati ng stars. Aims. The method here presented intends to minimize the effect of the gaps in the power spectra by gap-filling preserving the original information, that is, in the case of asteroseismology, the s tellar oscillation frequency content. Methods. We make use of a forward-backward predictor based on autoregressive moving average modelling (ARMA) in the time domain. The method MIARMA is particularly suitable for replacing invalid data such as those present in the light curves of the CoRoT satellite due to the pass through the South Atlantic Anomaly, and eventually for the data gathered by the NASA planet hunter Kepler. We select a sample of stars from the ultra-precise photometry collected by the asteroseismic camera on board the CoRoT satellite: theδ Scuti star HD 174966, showing periodic variations of the same order as the CoRoT observational window, the Be star HD 51193, showing longer time variations, and the solar-like HD 49933, with rapid time variations. Results. We showed that in some cases linear interpolations are less reliable to what was believed. In particular: the power spectrum of HD 174966 is clearly aliased when this interpolation is used for filling the gaps; the light curve of HD 51193 presents a m uch more aliased spectrum than expected for a low frequency harmonic signal; and finally, although the linear interpolation does not affect noticeably the power spectrum of the CoRoT light curve of the solar-like star HD 49933, the ARMA interpolation showed rapid variations previously unidentified that ARMA interprets as a signal. In any case, the ARMA interpolation method provides a cleaner power spectrum, that is, less contaminated by spurious frequencies. In conclusion, MIARMA appears to be a suitable method for filling gaps in the light curves of pulsating stars observed b y CoRoT since the method preserves their frequency content, which is a necessary condition for asteroseismic studies.

Limits in the application of harmonic analysis to pulsating stars

The work reported here demonstrates that it is possible to accurately determine surface gravities of

MIARMA: A minimal-loss information method for filling gaps in time series - Application to CoRoT light curves

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Precise surface gravities of δ Scuti stars from asteroseismology

Sct stars using the frequency content from high precision photometry and a measurement of the parallax. Using a sample of 10 eclipsing binary systems with a

Periodicities Within the Frequency Spectra of δ Scuti Stars Observed by Kepler

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Impact of gaps in the asteroseismic characterization of pulsating stars: I. The efficiency of pre-whitening★

Sct component and the unique

On the necessity of a new interpretation of the stellar light curves

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On the Origin of the Dense Frequency Spectra of Space Observed Intermediate Mass Pulsating Stars

Sct star discovered with a transiting planet, WASP-33, we were able to refine the