“…In this context, the autoregressive part of the model corresponds to random variation intrinsic to times between successive maximum (or minimum) brightnesses of a star, and the noninvertible moving average arises from differences between errors made in recording times of maximum (or minimum) brightness. The application of statistical methods to testing for period changes in variable stars has a long history in the astronomy literature; see, for example, Sterne and Campbell [24], Isles and Saw [4], Lombard [14], Percy and Colivas [18], Koen and Lombard [11,12] and Hart et al [3]. To our knowledge, only frequentist-type tests have been used to detect period changes in variable stars.…”