Helium-weak star
Type of star
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Helium-weak stars are chemically peculiar stars which have a weak helium lines for their spectral type.[1][2] Their helium lines place them in a later (i.e. cooler) spectral type than their hydrogen lines.[3]
Helium-weak star
Helium-weak stars are mid-to-late B-class stars with weaker than normal spectral lines of neutral helium, compared to normal stars with similar hydrogen line strengths. These are considered to be an extension of the Ap/Bp chemically-peculiar stars with slightly hotter temperatures. They often show similar increased abundances of heavy elements. The mechanism of atmospheric stratification of elements is thought to be responsible for both types of chemical peculiarity.[4][5]
This is a non-extensive list of helium-weak stars.[6][7]
| Star Name | Constellation | Apparent Magnitude (mv) | Class | Notes |
|---|---|---|---|---|
| 20 Eridani (EG Eridani) | Eridanus | 5.23 | B8/9 III | α2 CVn variable |
| 30 Capricorni | Capricornus | 5.38 | B5 II/III | |
| θ Hydri | Hydrus | 5.50 | B8 III/IV | Suspected Binary; |
| 22 Eridani (FY Eridani) | Eridanus | 5.53 | B9 IIIpSi (4200) | α2 CVn variable |
| HD 74196 | Vela | 5.61 | B7 Vn | Part of IC 2391 |
| HD 28843 (DZ Eridani) | Eridanus | 5.81 | B9 III | SX Arietis variable |
| 12 Canis Majoris (HK Canis Majoris) | Canis Major | 6.08 | B7 II/III | SX Arietis variable |
| HD 34797 (TX Leporis) | Lepus | 6.54 | B7 Vp | α2 CVn variable; binary |
| HD 35456 | Orion | 6.95 | B9 II/III | Binary |
Helium-strong star
Helium-variable star
V761 Centauri (a Centauri) is well-known for both the variability of its brightness and of its helium spectral lines. Stars of this type are referred to as helium-variable. This is thought to occur when one hemisphere of the star's atmosphere is helium-weak and one is helium-strong.[9]