Ultra-precise analysis of the light curves of CoRoT and Kepler δ Scuti stars

It is well known that the residuals of the multifrequency analysis of delta Scuti stars are correlated, giving rise to challenging features such as a plateau (HD 50844, HD 50870, HD 49434,...) of non-resolved frequencies with amplitude higher than the expected noise level. Several hypotheses have been advanced to explain these features: effective convection, rotation, non-linear interactions, etc. We have recently demonstrated that in some cases the underlying function describing the light variations of delta Scuti stars has not the property of being analytic. The strong consequence of this result is that the Fourier expansion on which the harmonic analysis is based could be not justified. In order to know the extension of this phenomenon among delta Scuti stars, we have used photometric data from CoRoT seismofield and a set of Kepler stars. The results show that this inconsistency in the application of harmonic analysis is almost ubiquitous to the delta Scuti pulsating stars.