Multiperiodicity and pulsation characteristics of beta Cephei
C. Aerts
- P. Mathias
- D. Gillet
- C. Waelkens
Received 8 November 1993; accepted 30 November 1993
Abstract:
High spectral and time resolution observations have been carried out on the
prototype of the beta Cephei stars. More than 650 spectra of high quality
(signal-to-noise ratio above 200) were obtained on the Si III (4553-4575
Å)
triplet lines. The radial velocity curves show a sinusoidal shape, with
a 2K-amplitude varying between 29 km/s and 35 km/s, while the gamma-velocity
remains roughly constant. The line parameters, i.e. width, intensity and
equivalent width show a different behaviour than the velocity variation,
since they change from night to night. A frequency analysis reveals for the
first time the presence of three pulsation periods in the radial velocity
variation. The moments method for mode identification is then succesfully
applied
to identify the three modes, indicating a main radial mode and two
small-amplitude low-degree (probably l=2) modes. It seems that non-radial
components are responsible for most of the line parameters variations, in which the three frequencies are also detected. In particular, the third frequency
detected in the velocity variation is the first present in the full width at
half maximum variation. This could be an effect of the larger associated
turbulence.
Keywords:
stars: early-type -- stars: individual: beta Cephei -- stars:
oscillations -- lines: profile
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