  Thanks to high-precision photometric data legacy from space telescopes like
CoRoT and Kepler, the scientific community could detect and characterize the
power spectra of hundreds of thousands of stars. Using the scaling relations,
it is possible to estimate masses and radii for solar-type pulsators. However,
these stars are not the only kind of stellar objects that follow these rules:
$\delta$ Scuti stars seem to be characterized with seismic indexes such as the
large separation ($\Delta\nu$). Thanks to long-duration high-cadence TESS light
curves, we analysed more than two thousand of this kind of classical pulsators.
In that way, we propose the frequency at maximum power ($\nu_{\rm max}$) as a
proper seismic index since it is directly related with the intrinsic
temperature, mass and radius of the star. This parameter seems not to be
affected by rotation, inclination, extinction or resonances, with the exception
of the evolution of the stellar parameters. Furthermore, we can constrain
rotation and inclination using the departure of temperature produced by the
gravity-darkening effect. This is especially feasible for fast rotators as most
of $\delta$ Scuti stars seem to be.
