Issue |
Astron. Astrophys. Suppl. Ser.
Volume 137, Number 3, June II 1999
|
|
---|---|---|
Page(s) | 407 - 418 | |
DOI | https://doi.org/10.1051/aas:1999256 | |
Published online | 15 June 1999 |
Multi-periodicity of the Be star η Centauri from spectroscopic and photometric observations
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
Send offprint request to: E. Janot-Pacheco
Received:
25
May
1998
Accepted:
1
December
1998
We present photometric data and 209 high-resolution, high signal-to-noise
ratio optical spectra of the Be star 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 ∼ 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 (η Cen)
© European Southern Observatory (ESO), 1999