Disentangling component spectra of κ Sco, a spectroscopic binary with a pulsating primary -: II.: Interpretation of the line-profile variability

We analyse the complex short-term Si III line-profile variability of the spectroscopic binary beta Cep star kappa Sco after orbit subtraction, before and after spectral disentangling. We refine the known oscillation frequency of the star: f(1) = 4.99922 c d(-1) and detect 2 f(1). Variability is also found at frequencies near f(2) similar or equal to 4.85 c d(-1) and f(3) similar or equal to 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(rot) of the star. The complex window function does not allow us to determine definite values for f2, f3, frot. The variability with f1 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. Sco 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.