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Title:
Degenerate stars with helium atmospheres
Authors:
Greenstein, J. L.
Affiliation:
AA(Hale Observatories, Pasadena, Calif.)
Publication:
Astrophysical Journal, vol. 210, Dec. 1, 1976, pt. 1, p. 524-532. (ApJ Homepage)
Publication Date:
12/1976
Category:
Astrophysics
Origin:
STI
NASA/STI Keywords:
HELIUM, HYDROGEN, STELLAR ATMOSPHERES, STELLAR MODELS, STELLAR SPECTROPHOTOMETRY, UBV SPECTRA, ABUNDANCE, ATMOSPHERIC MODELS, COLOR-COLOR DIAGRAM, COLORIMETRY
Comment:
A&AA ID. AAA018.126.040
DOI:
10.1086/154856
Bibliographic Code:
1976ApJ...210..524G

Abstract

The multichannel photometry of degenerate stars shows that, within a limited, critical region of the G - R, U - B color-color diagram, essentially all have atmospheres with high He/H ratios. The hotter members of this group have the strongest He I lines. The DB classification applies to stars from 13,000 or 15,000 K up to 22,000 or 25,000 K, calibrating G - R colors by the model atmospheres. The stars have less negative U - B than the models. At the lower temperature limit the transition to line-free DC spectra occurs abruptly. However, three stars show Ca II lines, although hotter than most DC's. The metal/helium content is therefore an additional variable. A preliminary interpretation is given in terms of the competition between accretion, gravitational diffusive separation, and shallow or deep convection.

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