Disentangling component spectra of kappa Scorpii, a spectroscopic binary with a pulsating primary. II. Interpretation of the line-profile variability
SourceAstronomy and Astrophysics, 432, 3, (2005), pp. 955-967
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Astronomy and Astrophysics
We analyse the complex short-term SiIII line-profile variability of the spectroscopic binary beta Cep star kappa Scorpii after orbit subtraction, before and after spectral disentangling. We refine the known oscillation frequency of the star: f<SUB>1</SUB>=4.99922 c d<SUP>-1</SUP> and detect 2f<SUB>1</SUB>. Variability is also found at frequencies near f<SUB>2</SUB>≃ 4.85 c d<SUP>-1</SUP> and f<SUB>3</SUB>≃ 5.69 c d<SUP>-1</SUP> 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<SUP>-1</SUP> which we interpret as the rotational frequency f<SUB>rot</SUB> of the star. The complex window function does not allow us to determine definite values for f<SUB>2</SUB>, f<SUB>3</SUB>, f<SUB>rot</SUB>. The variability with f<SUB>1</SUB> is interpreted as a prograde non-radial oscillation mode with spherical wavenumbers (l,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 kappa Scorpii 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. Based on observations obtained with the Coudé Échelle Spectrograph on the ESO CAT telescope and with the CORALIE échelle spectrograph on the 1.2-m Euler Swiss telescope, both situated at La Silla, Chile.
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