Delta Scuti (\( \delta \) Sct) stars are intermediate-mass pulsators whose intrinsic oscillations have been studied for decades. However, modelling their pulsations remains a real theoretical challenge, thereby even hampering the precise determination of global stellar parameters. Here we present a direct and precise measurement of the mean density of \( \delta \) Sct stars. This measurement is obtained from an observational relation that scales stellar mean density with an oscillation frequency pattern 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 of the star, thus allowing us to accurately determine the mass and the radius, constrain the evolutionary stage, and estimate the rotational velocity. This places tight constraints on stellar evolution theory and on the physical properties of planets orbiting A-type stars.

The objective of this work is to apply the recent techniques used with the pulsating spectrum of A-F stars [REFS] to study non-pertubative rotating models (SCF) [REFS] and  targets. The techniques are the Fourier transform (FT, from now), the autocorrelation function (ACF, from now), the histogram of frequency differences (HFD, from now), and the Echelle diagram (ED, from now). We are looking for the best procedure to obtain a reliable mode identification.