Helium-weak 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]

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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 though to be responsible for both types of chemical peculiarity. [4] [5]

This is a non-extensive list of helium-weak stars. [6] [7]

Caption text
Star NameConstellationApparent Magnitude (mv)ClassNotes
20 Eridani (EG Eridani) Eridanus 5.23B8/9 III α2 CVn variable
30 Capricorni Capricornus 5.38B5 II/III
θ Hydri Hydrus 5.50B8 III/IVSuspected Binary;
22 Eridani (FY Eridani) Eridanus 5.53B9 IIIpSi (4200) α2 CVn variable
HD 74196 Vela 5.61B7 VnPart of IC 2391
HD 28843 (DZ Eridani) Eridanus 5.81B9 III SX Arietis variable
12 Canis Majoris (HK Canis Majoris) Canis Major 6.08B7 II/III SX Arietis variable
HD 34797 (TX Leporis) Lepus 6.54B7 Vp α2 CVn variable; binary
HD 35456 Orion 6.95B9 II/IIIBinary

Helium-strong star

A related class of stars have anomalously strong helium lines in their spectra, and are known as helium-strong stars. [1] These are the more massive stars with classes of B1 to B3, compared to the helium-weak stars with classes of B5 to B9. [8] The following are examples:

Helium-variable star

V761 Centauri (a Centauri) is well-known 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]

See also

References

  1. 1 2 Landstreet, J. D.; Bohlender, David A. (1988). "Abundance and Magnetic Field Geometries of Helium-Strong and Helium-Weak Stars". Symposium - International Astronomical Union. 132: 309–312. Bibcode:1987BAAS...19..704B. doi: 10.1017/S0074180900035191 . ISSN   0074-1809.
  2. ↑ Preston, George W. (1974). "The Chemically Peculiar Stars of the Upper Main Sequence". Annual Review of Astronomy and Astrophysics. 12 (1): 257–277. Bibcode:1974ARA&A..12..257P. doi:10.1146/annurev.aa.12.090174.001353.
  3. ↑ "A Digital Spectral Classification Atlas - R. O. Gray". ned.ipac.caltech.edu. Retrieved 2019-05-31.
  4. ↑ Monier, Richard (2023). "The Behavior of Bp He-weak Stars in the Far UV-Paper XIII: HD 161480". Research Notes of the American Astronomical Society. 7 (9): 197. Bibcode:2023RNAAS...7..197M. doi: 10.3847/2515-5172/acfa9d .
  5. ↑ Alonso, M. S.; López-García, Z.; Malaroda, S.; Leone, F. (2003). "Elemental abundance studies of CP stars. The helium-weak stars HD 19400, HD 34797 and HD 35456". Astronomy and Astrophysics. 402: 331. Bibcode:2003A&A...402..331A. doi:10.1051/0004-6361:20030222.
  6. ↑ Jaschek, Mercedes; Jaschek, Carlos; Arnal, Marcelo (October 1969). "Helium-Weak Stars". Publications of the Astronomical Society of the Pacific. 81 (482): 651. Bibcode:1969PASP...81..650J. doi: 10.1086/128832 .
  7. ↑ Alonso, M. S.; López-García, Z.; Malaroda, S.; Leone, F. (April 2003). "Elemental abundance studies of CP stars. The helium-weak stars HD 19400, HD 34797 and HD 35456*". Astronomy and Astrophysics. 402: 331. Bibcode:2003A&A...402..331A. doi: 10.1051/0004-6361:20030222 .
  8. ↑ Faltová, N.; Kallová, K.; Prišegen, M.; Staněk, P.; Supíková, J.; Xia, C.; Bernhard, K.; Hümmerich, S.; Paunzen, E. (December 2021). "A case study of ACV variables discovered in the Zwicky Transient Facility survey". Astronomy & Astrophysics. 656. id. A125. arXiv: 2108.11411 . Bibcode:2021A&A...656A.125F. doi:10.1051/0004-6361/202141534.
  9. ↑ Bohlender, D. A.; Rice, J. B.; Hechler, P. (2010). "Doppler imaging of the helium-variable star a Centauri". Astronomy and Astrophysics. 520: A44. arXiv: 1007.0977 . Bibcode:2010A&A...520A..44B. doi:10.1051/0004-6361/201014157.
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