Aerts, C. ; De Cat, P. ; Cuypers, J. ; Becker, S. R. ; Mathias, P. ; De Mey, K. ; Gillet, D. ; Waelkens, C.

published in Astronomy and Astrophysics, 329, pp. 137-146 (1998)

Abstract: We present numerous high signal-to-noise spectroscopic data of the beta Cep star beta Crucis that were gathered during a total time span of 13 years. Although only one pulsation period was up to now known for beta Crucis, our data clearly point out that the star is multiperiodic. We find evidence for the presence of at least two new frequencies, besides the one already detected in photometric observations. Different modes are dominant in each of the observing seasons. We attempted an identification of the pulsation modes by means of the moment method and find that none of them is radial. The newly detected frequencies belong to modes that have l>=3, explaining why they were not detected photometrically. We also find that the star is seen at a low inclination angle. The average radial velocity varies for different seasons; its peak-to-peak amplitude amounts to 12km/s and confirms the binary nature of beta Crucis. We have determined the orbital parameters of the system and find an eccentric orbit (e=0.38) with a period of 5 years. From spectroscopic arguments we infer a B2V companion. Based on observations obtained at the European Southern Observatory, Chile

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