EDP Sciences
Free Access
Volume 394, Number 1, October IV 2002
Page(s) 137 - 149
Section Formation, structure and evolution of stars
DOI https://doi.org/10.1051/0004-6361:20021105

A&A 394, 137-149 (2002)
DOI: 10.1051/0004-6361:20021105

Variability and pulsations in the Be star 66 Ophiuchi

M. Floquet1, C. Neiner1, 2, E. Janot-Pacheco3, 1, A. M. Hubert1, S. Jankov4, 5, J. Zorec6, D. Briot1, J. Chauville1, N. V. Leister3, J. R. Percy7, D. Ballereau1 and A. G. Bakos7

1  Observatoire de Paris-Meudon, GEPI, FRE/2459, 92195 Meudon Cedex, France
2  Sterrenkundig Instituut Anton Pannekoek, Universiteit van Amsterdam, Kruislaan 403, Amsterdam, Netherlands
3  Instituto de Astronomia, Geofísica e Ciências Atmosféricas da Universidade de São Paulo, CUASO 05508-900 São Paulo, Brazil
4  Observatoire de la Côte d'Azur, FRESNEL, CNRS UMR 6528, BP 4229, 06304 Nice Cedex, France
5  Astronomska Opservatorija Beograd, MNTRS 1940, Volgina 7, 11050 Beograd, Yugoslavia
6  Institut d'Astrophysique de Paris, 98bis boulevard Arago, 75014 Paris, France
7  Erindale Campus and Department of Astronomy, University of Toronto, Mississauga, ON L5L 1C6, Canada

(Received 30 Avril 2002 / Accepted 31 July 2002 )

66 Oph is a Be star seen under a moderate inclination angle that shows strong variability from UV to IR wavelengths. A concise review of long-term variability history is given. High resolution, high S/N spectroscopic observations obtained in 1997, 1998 and 2001 and spectropolarimetric observations obtained in 2000 are presented. These observations occurred during a long-term decrease of H $\alpha$ intensity. Fundamental parameters of the star have been revisited from Barbier-Chalonge-Divan (BCD) calibrations. New $V \sin i$ values are obtained using Fourier transforms applied to observed helium lines and a rotational frequency $f_{\rm rot} = 1.29$ c d -1 is determined. Time series analysis and Fourier Doppler Imaging (FDI) of $\ion{He}{i}$ lines (4713, 4921, 5876 and 6678 Å) lead for the first time to the detection of multi-periodicity in 66 Oph. The two main frequencies found are f = 2.22 c d -1 and f = 4.05 c d -1 . They are attributed to non-radial pulsations and can be associated with mode degree $\ell = 2$ and $\ell = 3$, respectively. Inspection of Stokes  V profiles suggests the presence of a weak Zeeman signature but further observations are needed to confirm the detection of a magnetic field in 66 Oph.

Key words: stars: emission-line, Be -- stars: activity -- stars: individual: 66 Oph -- stars: oscillations -- stars: magnetic field

Offprint request: M. Floquet, michele.floquet@obspm.fr

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© ESO 2002