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

Free access article

Issue		A&A Volume 432, Number 3, March IV 2005


Page(s)		955 - 967
Section		Stellar structure and evolution
DOI		http://dx.doi.org/10.1051/0004-6361:20041444

A&A 432, 955-967 (2005)
DOI: 10.1051/0004-6361:20041444

II. Interpretation of the line-profile variability

K. Uytterhoeven¹, M. Briquet¹, C. Aerts^{1, 2}, J. H. Telting³, P. Harmanec^{4, 5}, K. Lefever¹ and J. Cuypers⁶

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 Holesovickách 2, 180 00 Praha 8, Czech Republic
⁵ Astronomical Institute, Academy of Sciences, 251 65 Ondrejov, 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 $\beta\,$ Cep star after orbit subtraction, before and after spectral disentangling. We refine the known oscillation frequency of the star: f₁=4.99922 c $\,$ d^-1 and detect 2f₁. Variability is also found at frequencies near $f_2\simeq 4.85$ c $\,$ d^-1 and $f_3\simeq 5.69$ 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 [0.22,0.30] c d^-1 which we interpret as the rotational frequency $f_{\rm rot}$ of the star. The complex window function does not allow us to determine definite values for $f_2, f_3, f_{\rm rot}$ . The variability with f₁ is interpreted as a prograde non-radial oscillation mode with spherical wavenumbers $(\ell,m)=(2,-1)$ or (1,-1). 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.

Key words: binaries: spectroscopic -- stars: oscillations -- line: profiles -- stars: individual:

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