are non supergiant B-type stars that exhibit or have exhibit emission lines over the photospheric spectrum. Be stars are hot B-type stars (effective temperature 10 000 to 30 000 K) with luminosity class III to V (ie : non supergiant stars) whose spectrum has shown at least once an emission line – usually hydrogen Balmer line. Sometimes, other emission lines are visible, for exemple neutral helium. Even when the spectrum goes back to “normal”, the star remains in the Be star class.
The frequency of the variations of the profile lines covers a very broad range since some Be stars can show certain line-profile changes in a few hours or minutes whereas others can remain stable during years. Sometimes several cycles of variations with very different periods can be superimposed. The emission features themselves have a great variety of profiles. A typical situation is the shell configuration in which a narrow and deep absorption line is in the center of a broad emission line. Some time photospheric absorption line wings is visible on both sides of the emission line profile. It is probable that the majority of the Be stars present a "shell" phase to one moment of their life. The phenomena behind those emission are still being actively studied and amateurs with high resolution spectrographs such as Lhires III or L-200, can now contribute to the monitoring of those stars.
- 8" f/4 Newton
- Atik 414
Gamma Cas H-alpha
- L200 Spectrograph 1800 grating 24µm slit
- ASI1600 MM 2x2 bin
- L200 Spectrograph 1800 grating 29µm slit
- ASI1600MM 2x2 bin
- Site: Berlin, Germany