SIMBAD references

We have studied the period changes in 15 RV Tauri stars, using the Eddington- Plakidis hypothesis, which assumes that the (O-C) diagrams can be interpreted as a superposition of random errors in the measured times of minimum, and random cycle-to-cycle fluctuations in the period. Except for three stars for which the data are sparse, the hypothesis fits the (O-C) data very well, suggesting that the assumptions are correct. The magnitude of the random period fluctuations does not appear to correlate with any obvious physical property of stars.