Line-profile variations of the double-lined spectroscopic binary $\mathsf{\kappa}$ Scorpii

Abstract

We present a total time series of high signal-to-noise, high-resolution spectra of the SiIII 4552:6, 4567: 8a nd4574:8 A lines of the fast-rotating, spectroscopic binary and Cephei star Scorpii. Among this data set is a sample of 422 spectra of intensive monitoring during eight subsequent nights in July 1997. We nd variability of the line proles on two time-scales: a variation of several months as a result of the orbital motion and rapid variations of a few hours, which are explained in terms of non-radial pulsation modes. From the total dataset, covering a time span of 9 years, we derive for the rst time the orbital parameters of Scorpii and nd an orbital period of 195 days. The complex patterns on the grayscale representations of the residual SiIII 4552:6 A proles with respect to the average prole point towards more than one (non-axisymmetric) pulsation mode. A frequency analysis of the three normalised velocity moments conrms the main period of 4.80 hours and the second period of 4.93 hours, which were previously derived from photometric data. We attempt an identication of the pulsation modes by means of the moment method and line-prole tting and nd that Scorpii pulsates in a main prograde sectoral mode of degree 1 or 2 and in an additional tesseral mode for which l =5 ,m =1a re the most likely wavenumbers. In the variations of the line proles we nd indications for the presence of additional pulsation modes.