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Table 1
Spectral classification scheme.
| sdB | H, (He i) |
| sdOB | H, He i, He ii |
| sdO | H, He ii (H-rich) or He ii, (H) (He-rich) |
| He-sdB | He i, (H) |
| He-sdOB | He i, He ii, (H) |
| He-sdO | He ii, (He i, H) |
| sdO/B+K/G/F/A | sdO/B with visible MS companion |
|
|
|
| sdO/BV | Pulsator |
| sdO/B+WD/dM/BD | sdO/B with close invisible companion |
Notes. For each class the species with observed lines in the spectrum are given in a sequence of relative strength. The strongest lines are always coming first. Species in parentheses can be present, but do not have to be.
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