Analysis of the frequency spectrum of the spectroscopic binary Cephei star Scorpii

We present an analysis of line-profile variations of the spectroscopic binary Cephei star Scorpii, based on 421 high-resolution and high-signal to noise spectra of the SiIII lines centered at 4568 A taken during 8 subsequent nights in July 1997. Scorpii (HD 158926) is known as a triple system (De Mey et al. 1997, A&A 324, 1096) , with the primary and secondary in a close but eccentric (e = 0.256$) orbit of P orb = 6.26 days (Uytterhoeven et al., in preparation).
A study of the pulsational variability by means of an analysis of line-profile variations leads to the detection of at least 6 frequencies. This result is an improvement with regard to previous (photometrical) studies since only one pulsation mode was detected before our work (Shobbrook & Lomb 1972, MNRAS 156,181; Lomb & Shobbrook 1975, MNRAS 173, 709; Watson 1988, Ap&SS 140, 255).
A We used a combination of different mode-identification techniques e.g. line-profile fitting, the moment method and the IPS method to extract pulsational characteristics from the line-profile variations. All methods point towards the presence of nonradial pulsation modes, which is in contrary to the suggestion of Watson (1988, Ap&SS 140, 255) that Scorpii pulsates in a radial pulsation mode.
The detection of at least 6 pulsational frequencies, of which 5 at rather low amplitude, and the promissing possibility of the presence of additional frequencies, makes $\lambda$ Scorpii a very interesting target for the future asteroseismological space missions.}

 
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