Evidence of Tidal Effects in Some Pulsating Stars. II. Lacertae and β Cephei

Published observations of two j3 CMa stars are analyzed. The star 16 Lac is a single-line spectroscopic binary with a circular orbit of 124096 period; the primary star pulsates in a primary period of 0.169166. In addition, two nonradial modes are excited, apparently by coupling to the primary pulsation through rotation and through a tidal resonance at 0.2 orbital period, respectively. The star j3 Cep is also found to be a single line spectroscopic binary with an orbit of large eccentricity of 10d1893 period The orbital velocity of the primary is small because of a large primary-to-secondary mass ratio; the orbital elements are therefore rather uncertain, but they show that the primary pulsation (P1 = 0d19049) undergoes a strong, nonresonant amplitude modulation around the time of periastron passage, with maximum ampli- tude probably occurring at maximum tidal compression. A simplified theory of resonant and nonresonant tidal modulation is presented. A summary is given of presently available information relating to tidal modulations of five /3 CMa stars and three ~ Sct stars