Beta Cephei variable

As a Beta Cephei stars ( GCVS nomenclature abbreviation: BCEp ) refers to a class pulsationsveränderlicher stars, named after their prototype β Cephei, whose brightness sinusoidally in a first approximation with an amplitude of up to 0.2 mag with a period between 3 and 7 fluctuates hours.

Beta Cephei stars are stars with spectral types between B0.5 and B2, and are at, or slightly above the main sequence. The classified luminosity classes range from I to V, most of the stars in the luminosity classes IV and III ( sub- giants and giants). They belong to population I and have a mass in the range of 8 to 18 solar masses. Even with these pulsating variables, the oscillations of the stellar atmosphere are excited by the kappa mechanism. In the Beta Cephei stars, it is the ionization of iron and not the hydrogen, as in most other pulsating variable stars. Here, the restoring force of the vibrations of both gravity and the pressure.

Until a few years ago it was assumed that most beta Cephei stars pulsate only radially. When observations from satellites such as MOST ( satellite), Kepler and COROT all beta Cephei stars also showed non-radial pulsation, ie wave crests and troughs rotate the star in addition to the radial oscillations. Satellite observations avoid the problematic separation of vibrations with different frequencies only slightly, since the interruptions during the day and by the weather do not matter from space. Superimposing itself closely spaced non-radial and / or radial pulsation frequencies, only the beat of the frequencies is visible in the total light of the star. Typical beat periods are in the range of days to weeks.

The concept of beta Canis Majoris stars is interpreted differently. He is sometimes equated with the beta Cephei stars and sometimes exclusively used for multi- periodic Beta Cephei stars. However, since all beta Cephei stars seem to be multi- periodic, this class is rarely used.

Known Beta Cephei stars

• β Cep
• β CMa
• γ Peg