Cross Correlation Detection of Rapid Stellar Variability Using Two Telescopes

Abstract

The study of rapid, small amplitude stellar variability is handicapped by scintillation and photon noise. Flickering on time scales corresponding to bandwidths B ≳ 0.1 Hz may be expected of a variety of irregular variables including dwarf novae and X-ray binaries. Stochastic variability is harder to detect than periodic variability because its spectrum is likely to be a continuum, not necessarily distinguishable from the spectrum of the noise due to scintillation, extinction variations, sky radiance variations and photon statistics. The proposed correlation technique provides a means whereby systematic errors may be largely eliminated and the full statistical threshold limit achieved. Simultaneous observations of a suspected variable by an array of two telescopes separated by a base line exceeding the noise correlation distance are proposed.