Disentangling component spectra of , a spectroscopic binary with a pulsating primary^*

II. Interpretation of the line-profile variability

¹ Institute of Astronomy, Katholieke Universiteit Leuven, Celestijnenlaan 200 B, 3001 Leuven, Belgium e-mail: Katrien.Uytterhoeven@ster.kuleuven.ac.be
² Department of Astrophysics, University of Nijmegen, PO Box 9010, 6500 GL Nijmegen, The Netherlands
³ Nordic Optical Telescope, Apartado de Correos 474, 38700 Santa Cruz de La Palma, Spain
⁴ Astronomical Institute of the Charles University, V Holešovičkách 2, 180 00 Praha 8, Czech Republic
⁵ Astronomical Institute, Academy of Sciences, 251 65 Ondřejov, Czech Republic
⁶ Royal Observatory of Belgium, Ringlaan 3, 1180 Brussel, Belgium

Received: 10 June 2004
Accepted: 31 October 2004

Abstract

We analyse the complex short-term  line-profile variability of the spectroscopic binary Cep star after orbit subtraction, before and after spectral disentangling. We refine the known oscillation frequency of the star:  c d^-1 and detect . Variability is also found at frequencies near  c d^-1 and  c d^-1 or their aliases. These frequencies are not significant if we consider the spectra alone, but they survive our selection after the consideration that they were derived previously from independent ground-based and space photometry by different teams. Moreover, we find dominant variability in the equivalent width with a frequency in the interval  c d^-1 which we interpret as the rotational frequency f_rot of the star. The complex window function does not allow us to determine definite values for . The variability with f₁ is interpreted as a prograde non-radial oscillation mode with spherical wavenumbers or . The additional frequencies are explained in terms of rotational modulation superposed to the main oscillation. We also point out that we cannot disprove the variability in  to originate from co-rotating structures. KOREL disentangling preserves the large-amplitude line-profile variability but its performance for complex low-amplitude variability remains to be studied in detail.