Department of Astronomy and
Astrophysics, University of Toronto, Mississauga ON, L5L 1 C6, Canada
Presented at the AAVSO Symposium on
Mira Stars, April 26, 2004; received December 21, 2004; accepted January 5, 2005
Abstract 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.