The analysis of indexed astronomical time series – X. Significance testing of O − C data
Abstract
It is assumed that O − C (‘observed minus calculated’) values of periodic variable stars are
determined by three processes, namely measurement errors, random cycle-to-cycle jitter in
the period, and possibly long-term changes in the mean period. By modelling the latter as a
random walk, the covariances of all O − C values can be calculated. The covariances can then
be used to estimate unknown model parameters, and to choose between alternative models.
Pseudo-residuals which could be used in model fit assessment are also defined. The theory is
illustrated by four applications to spotted stars in eclipsing binaries.