SIMBAD references

Variogram analysis is applied to time series of variable stars. This method allows to characterize time-scales of varying signals. It is well suited for periodic and pseudo-periodic signals. The aspects of robustness, bin positions and bin widths for the variogram estimator are assessed, evaluated with the help of simulations and adapted to the Hipparcos photometry. For instance variogram methodology is successfully applied for the detection of spurious periods, the estimation of measurement noise and the analysis of the pseudo-period of some typical Hipparcos variable stars.