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. 413-415
Editor: W. Wenzel
Remarks on Photometric and Spectroscopic Variations of the B9p Star ET And
Gerhard Scholz and Ewald Gerth
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

Abstract
The B9p star ET And (HD 219749) shows light and radial velocity variations with periods in scales of months (Ouchrabka, Grygar), days (Hildebrandt, Hempelmann), hours (Hildebrandt, Hempelmann, Panov), and minutes (Panov), the origin of which and their mutual relationship being very puzzling. To bring light into this muddle of periods, the authors - together with K.P. Panov of the Bulgarian National Observatory - carried out simultaneous photometric and spectroscopic observations, which allowed to determine the phase relation between radial velocity and light variations. The striking result was, that the relation of the periods in the hour-scale proved to be exactly 2:1. Discussing the results, the possibility of pulsations in the order of minutes to hours is considered to be hardly probable. More probable seems to be an orbital motion in a binary system with excitation of tides, which produce nonradial pulsations with the expected characteristic frequency given by the physical parameters of the star.

P 74. Scholz G., Gerth E.:
Remarks on Photometric and Spectroscopic Variations of the B9p Star ET And
Meeting on Observation and Interprtation of Pulsating Stars, Sonneberg 4-8 Sep. 1989
ed. W. Wenzel, Veroeff. d. Sternwarte Sonneberg 10 (1990) 5, 413-415
Abstract www.ewald-gerth.de/74abs.htm