Astron. Astrophys. 364, L85-L88 (2000)

Letter to the Editor

Properties and nature of Be stars

XX. Binary nature and orbital elements of  Cas

P. Harmanec ^1,2, P. Habuda ³, S. tefl ², P. Hadrava ², D. Koráková ^4,2, P. Koubský ², J. Krtika ^4,2, J. Kubát ², P. koda ², M. lechta ² and M. Wolf <sup>1

1</sup> Astronomical Institute of the Charles University, V Hole ovi kách 2, 180 00 Praha 8, Czech Republic
² Astronomical Institute of the Academy of Sciences, 251 65 Ond ejov, Czech Republic
³ Faculty of Mathematics and Physics of the Charles University, Ke Karlovu 3, 121 16 Praha 2, Czech Republic
⁴ Masaryk University, Faculty of Science, Department of Theoretical Physics and Astrophysics, 611 37 Brno, Czech Republic

Received 20 September 2000 / Accepted 27 November 2000

Abstract

An analysis of accurate radial velocities (RVs) of the Be star  Cas from 295 Reticon spectrograms secured between October 1993 and May 2000 allowed us to prewhiten the RVs for the long-term changes and to obtain the first orbital RV curve of this star. The orbital period is 20359 and the orbit has an eccentricity of 0.26. The orbital motion is de- tectable even in the published velocities, based on photographic spectra. This implies that  Cas is a primary component of a spectroscopic binary. The secondary has a mass of about 1 , appropriate for a white dwarf or a neutron star, but it could also be a normal late-type dwarf. The ultimate solution of the dispute whether the observed X-ray emission is associated with the secondary or with the primary will need further dedicated studies.

Key words: stars: binaries: spectroscopic stars: emission-line, Be stars: individual: fl Cas

Send offprint requests to: P. Harmanec (hec@sunstel.asu.cas.cz)

SIMBAD Objects

Contents

• 1. Introduction
• 2. Observations and reductions
• 3. Analysis of RV changes
• 4.  Cas as a spectroscopic binary
• 5. Probable basic physical properties of  Cas
• 6. Discussion
• Acknowledgements
• References

© European Southern Observatory (ESO) 2000

Online publication: January 29, 2001
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