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Astron. Astrophys. 329, 137-146 (1998)


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Evidence for binarity and multiperiodicity
in the [FORMULA] Cephei star [FORMULA] Crucis *

C. Aerts 1,**, P. De Cat 1, J. Cuypers 2, S.R. Becker 3, P. Mathias 4, K. De Mey 1, D. Gillet 5 and C. Waelkens 1

1 Instituut voor Sterrenkunde, Katholieke Universiteit Leuven, Celestijnenlaan 200 B, B-3001 Heverlee, Belgium
2 Koninklijke Sterrenwacht van Belgiï, Ringlaan 3, B-1080 Brussels, Belgium
3 Institut für Astronomie und Astrophysik der Universität München, Scheinerstraße 1, D-81679 München, Germany
4 Observatoire de la Côte d'Azur, Département Fresnel, U.R.A. 1361, BP 229, F-06304 Nice Cedex 4, France
5 Observatoire de Haute Provence - CNRS, F-04870 Saint-Michel l'Observatoire, France

Received 11 March 1997 / Accepted 12 August 1997

Abstract

We present numerous high signal-to-noise spectroscopic data of the [FORMULA] Cep star [FORMULA] Crucis that were gathered during a total time span of 13 years. Although only one pulsation period was up to now known for [FORMULA] 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 [FORMULA], 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 12 km/s and confirms the binary nature of [FORMULA] Crucis. We have determined the orbital parameters of the system and find an eccentric orbit ( [FORMULA] ) with a period of 5 years. From spectroscopic arguments we infer a B2V companion.

Key words: line: profiles – stars: early-type – stars: oscillations – stars: individual: fi Crucis

* Based on observations obtained at the European Southern Observatory, Chile
** Postdoctoral Fellow, Fund for Scientific Research, Flanders

© European Southern Observatory (ESO) 1998

Online publication: November 24, 1997
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