Meeting on "Observation and Interpretation of Pulsating Stars". Proceedings of the Meeting of subproject No. 3 "Nonstationary Stars" of the Multilateral Cooperation of the Academies of Sciences of Socialist Countries, held at Sonneberg, 1989 Sep. 4-8. Vol. 10, Iss. 11, p. 415-420
Editor: W. Wenzel
The Variable Star ET Andromedae -
a Tidally Excited Pulsator?

Ewald Gerth and Gerhard Scholz
Academy of Sciences of the GDR, Central Institute of Astrophysics, Potsdam (GDR)
Zentralinstitut für Astrophysik der Akademie der Wissenschaften der DDR, DDR-1500 Potsdam Telegrafenberg

Spectroscopic observations of the B9p star ET And secured at the Bulgarian National Observatory Rozhen in the years 1981-1984, show clearly a radial velocity period of 0.198 d - with a ratio to the photometric period of exactly 2:1. This behavior would hint at a close binary system with tidal bulges. Considering the excitation of pulsations, then the eigenfrequency of a nonradially pulsating star would be in agreement with the physical parameters of the star. Obviously, the pulsation appears as a wave running around the star and being in resonance with an orbiting companion.

P 75. Gerth E., Scholz G.:
The Variable Star ET Andromedae - a Tidally Excited Pulsator?
Meeting on Observation and Interpretation of Pulsating Stars, Sonneberg 4-8 Sep. 1989
ed. W. Wenzel, Veroeff. d. Sternwarte Sonneberg 10 (1990) 5, 415-420