Interpretation of the variability of the β Cephei star λ Scorpii ^*

II. The line-profile diagnostics

¹ Institute of Astronomy, Catholic University Leuven, Celestijnenlaan 200 B, 3001 Leuven, Belgium e-mail: katrien.uytterhoeven@ster.kuleuven.ac.be
² Mercator Telescope, Calle Alvarez de Abreu 70, 38700 Santa Cruz de La Palma, Spain
³ Nordic Optical Telescope, Apartado 474, 38700 Santa Cruz de La Palma, Spain
⁴ Department of Astrophysics, University of Nijmegen, PO Box 9010, 6500 GL Nijmegen, The Netherlands
⁵ Department of Physics and Astronomy, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208, USA
⁶ Department of Physics and Astronomy, The Open University, Milton Keynes, MK7 6AA, UK

Received: 4 May 2004
Accepted: 15 July 2004

Abstract

We present the results of our analysis of a time series of high-resolution spectra of the multiple β Cephei star λ Scorpii. The data set has a total time-span of more than 5000 days and includes an intensive monitoring campaign during 8 consecutive nights. We confirm the presence of a dominant frequency  c d^-1 in the data. We show that the amplitude is variable in time according to the light-time effect in the multiple system. The dominant frequency is identified as a prograde dipole pulsation mode. From modelling of the amplitudes and phases across the profiles we derive pulsational parameters, the inclination angle and  km s^-1. From a comparison between theoretically calculated forcing eigenfrequencies induced by the close companion and the eigenfrequencies of the observed oscillation mode we find no tidal enhancement or excitation of the pulsation mode of λ Scorpii. We find indications for the presence of additional frequencies with low amplitudes.