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New periodic variables from the Hipparcos epoch photometry
Two selection statistics are used to extract new candidate periodicvariables from the epoch photometry of the Hipparcos catalogue. Theprimary selection criterion is a signal-to-noise ratio. The dependenceof this statistic on the number of observations is calibrated usingabout 30000 randomly permuted Hipparcos data sets. A significance levelof 0.1 per cent is used to extract a first batch of candidate variables.The second criterion requires that the optimal frequency be unaffectedif the data are de-trended by low-order polynomials. We find 2675 newcandidate periodic variables, of which the majority (2082) are from theHipparcos`unsolved' variables. Potential problems with theinterpretation of the data (e.g. aliasing) are discussed.
| Characterization of variable stars by robust wave variograms: an application to HIPPARCOS mission
Variogram analysis is applied to time series of variable stars. Thismethod allows to characterize time-scales of varying signals. It is wellsuited for periodic and pseudo-periodic signals. The aspects ofrobustness, bin positions and bin widths for the variogram estimator areassessed, evaluated with the help of simulations and adapted to theHipparcos photometry. For instance variogram methodology is successfullyapplied for the detection of spurious periods, the estimation ofmeasurement noise and the analysis of the pseudo-period of some typicalHipparcos variable stars.
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