SIMBAD references

About one-third of pulsating red giants show secondary periods which are an order of magnitude longer than the main pulsation period. The causes of the long secondary periods (LSPs) are unknown, but some may result from the effects of a binary companion. We have carried out self-correlation analysis of EG And, AX Per, CH Cyg, CL Cyg, AG Peg, and Z And, using both visual and photoelectric data. Five of the stars show variability which is orbit related: the time scale is equal to the orbital period, or half the orbital period. However, the pulsational variability, if any, is very low amplitude, compared with normal red giants of the same spectral type.