Free Access
Astron. Astrophys. Suppl. Ser.
Volume 137, Number 3, June II 1999
Page(s) 407 - 418
Published online 15 June 1999
DOI: 10.1051/aas:1999256

Astron. Astrophys. Suppl. Ser. 137, 407-418

Multi-periodicity of the Be star $\eta$Centauri from spectroscopic and photometric observations

E. Janot-Pacheco1 - S. Jankov1 - N.V. Leister1 - A.M. Hubert2 - M. Floquet2

Send offprint request: E. Janot-Pacheco

1 - Instituto Astronômico e Geofísico, Universidade de São Paulo C.P. 3386, 01060-970, São Paulo, SP, Brazil
2 - Observatoire de Paris, Section d'Astrophysique de Meudon, URA 335 du CNRS/DASGAL, F-92195 Meudon Cedex, France

Received May 25; accepted December 1, 1998


We present photometric data and 209 high-resolution, high signal-to-noise ratio optical spectra of the Be star $\eta$ Centauri obtained in 1993 and 1995, respectively. Time series analysis of these and other data, performed using the CLEAN, CLEANEST and Fourier Doppler Imaging techniques, show the presence of multiperiodic variations. They are interpreted in terms of low and high order non-radial pulsation modes. A strong frequency of 1.29 c/d is detected in line profile and photometric variations. It is attributed to a mode with l=2. Other high amplitude signals present in spectroscopic data are 1.78 c/d, 3.82 c/d and 4.51 c/d. A frequency of 1.48 c/d appearing in spectroscopic data is compatible with the 1.56 c/d periodicity largely dominant in observations taken prior to 1993. The corresponding "superperiods" for four of the frequencies are commensurate at the 8% level. The star showed period and non-radial pulsation degree variations in timescales as short as $\sim $1.5 hour. The dominant mode apparently alternates between l=2 and l=4 every other day during the eight day time span. This could be a modulation linked to the superperiod or to the stellar rotation. The main periodicities detected in our analysis are compatible with theoretical unstable g modes in SPB variables. Short time scale variability (1-3 hr), typical of high-order p modes is also systematically present.

Key words: stars: emission-line, Be -- stars: oscillations -- stars: individual ($\eta$ Cen)

SIMBAD Objects

Copyright The European Southern Observatory (ESO)

Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.

Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.

Initial download of the metrics may take a while.