Variable Stars: which Nyquist Frequency?
L. Eyer, Paul Bartholdi, Observatoire De Gen`eve, Ch- Sauverny · Springer Link (Chiba Institute of Technology) · 1998
. In the analysis of variable stars, the problem of sampling is central. This article focusses on the determination of the Nyquist frequency. It is well defined in the case of regular sampling. However, the time series of variable stars observations are generally unevenly sampled. Fourier analysis using the spectral window furnishes some clues about the equivalent Nyquist frequency in the irregular case. Often it is pushed very high, and thus very short periods can be detected. A specific example is shown, drawn from MACHO databases. Key words: Variable stars -- Time series -- Nyquist frequency 1. Introduction When variable stars observations are analyzed, two major problems arise. First, there are constraints on the sampling times. They can't always be chosen, because of weather conditions or other observing restrictions. Secondly, the stars, even if they are periodic, can have an extremely wide range of periods and behaviors. Therefore, astronomers would like to know up to which hi...