A possible explanation of the helium deficiency observed in BP stars

Details A possible explanation of the helium deficiency observed in BP stars A possible explanation of the helium deficiency observed in BP stars

Dec 1980

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1980pazh....6..723k&link_type=abstract

(Pis'ma v Astronomicheskii Zhurnal, vol. 6, Nov.-Dec. 1980, p. 723-729.) Soviet Astronomy Letters, vol. 6, Nov.-Dec. 1980, p. 38

Astronomy and Astrophysics

Astronomy

A Stars, Abundance, B Stars, Helium, Magnetic Stars, Stellar Atmospheres, Iron, Manganese, Thermodynamic Equilibrium, Ultraviolet Spectra

Scientific paper

The underabundance of helium in the atmospheres of Ap, Bp, and helium-weak stars is investigated. It is pointed out that the weakening of the He I lines in the spectra of these stars in the temperature range 14,000-20,000 K might result not simply from a true helium deficiency but also from the conditions under which He is excited which are characterized by pronounced departure from local thermodynamic equilibrium. Non-LTE excitation of He I can be induced in the atmosphere of hot, chemically peculiar stars by interaction of the 584 A He I resonance line with ultraviolet lines of the Fe III, Fe IV, and Mn IV ions. Intensity anomalies are predicted for some of these lines.

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