SIMBAD references

We have studied the period change in the peculiar Population II Cepheid RU Cam, which abruptly decreased in amplitude in 1965-1966. The O-C diagram prior to 1965-1966 can best be explained as the superposition of small, random, cycle-to-cycle changes in period, plus a constant linear decrease whose timescale (31,000 yr) is consistent with evolutionary predictions. The O-C diagram after 1965-1966 can best be explained as the superposition of much larger random, cycle-to-cycle changes (which mask the evolutionary changes), plus wavelike changes in O-C on a timescale of 10-20 periods. These–and the variations in the amplitude of the star that occur on the same timescale–may be due to multiperiodicity.