Quasi-periodicities in the periodograms of Corot Delta Scuti stars

Periodic patterns are not expected to be found in the frequency spectra of delta-Scuti stars, as in solar-like pulsators. However, some efforts have been carried out in order to find any signal of periodicity in this type of stars (Handler et al., 1997; Breger et al., 1999, 2009). These works used ground-base observations and the results have not been conclusive. In our study we have used data from CoRoT of two delta-Scuti stars poorly known. We have found a clear quasi-periodic pattern in their frequency spectra. Furthermore, we have identified this pattern with a signal of the large separation (using its definition) and that this large separation is a function of the mean density of the star. Because of this fact, we call this quasi-periodicity as a new observable and we have used it to reduce the uncertainty box of our pulsating objects.