Variability and pulsations in the Be star 66 Ophiuchi^*

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

Corresponding author: M. Floquet, michele.floquet@obspm.fr

Received: January 1900
Accepted: 31 July 2002

Abstract

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 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 Hα intensity. Fundamental parameters of the star have been revisited from Barbier-Chalonge-Divan (BCD) calibrations. New values are obtained using Fourier transforms applied to observed helium lines and a rotational frequency  c d^-1 is determined. Time series analysis and Fourier Doppler Imaging (FDI) of 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  c d^-1 and  c d^-1 . They are attributed to non-radial pulsations and can be associated with mode degree and , 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.