RS Oph in quiescence. The AAVSO provides a wonderful light curve from 1934 to 2004 composed of 47,000 mag (in 0.01-year time
bins). The eruptions (indicated in time by the long vertical lines) and the post-eruption dips have been clipped out so we
can only see the changes of the system in quiescence. We see a messy light curve, with flares on all time scales, and decadal
episodes of flares and relative calm. A Fourier transform of this light curve shows a peak at 2030 days, with the putative
maxima indicated by the short vertical lines along the top. This apparent periodicity is only a result of the crude alignment
between a handful of flares, and indeed a detailed quantitative analysis shows that for flares as seen for RS Oph with random
times we will always view a false periodicity as good as seen in the real light curve. That is, the periodicity is not significant.