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Analysis of helium-rich subdwarf O stars. 1: NLTE models, methods, and fits for 21 Palomar Green survey sdOsAtmospheric parameters for 21 helium-rich hot subdwarf O stars from the Palomar Green survey are found from fits of non-local thermodynamic equilibrium (NLTE) models to optical spectra. About 250 new NLTE models in the parameter range T(sub eff) from 35,000 to 65,000 K, log (g) from 4.0 to 6.5, and epsilon(He) from 50% He to 99% He have been calculated. A fit for each object is presented. Estimated distances and luminosities are calculated, assuming a mass of 0.5 solar masses. Large distances above the Galactic plane are found, and this implies that the majority of the sdO stars belong to a different stellar population than the sdB, planetary nebulae and white dwarf stars. Possibilities may include the halo and a 'thick disk.' Kinematical data from the literature are also discussed in view of the found distances. Five of the stars have been observed, modeled, and analyzed by Dreizler et al., and significant differences exist between their results and ours for these stars. The reason for these differences is not yet known, but the problem does not alter the conclusions about population membership that we present.
Document ID
19950040879
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Thejll, P.
(Niels Bohr Institute Copenhagen, Denmark)
Bauer, F.
(Universitat Muenchen Muenchen, Germany)
Saffer, R.
(Space Telescope Science Institute, Baltimore, MD United States)
Liebert, J.
(University of Arizona, Tucson, AZ United States)
Kunze, D.
(Universitat Muenchen Muenchen, Germany)
Shipman, H. L.
(University of Delaware, Newark, DE United States)
Date Acquired
August 16, 2013
Publication Date
October 1, 1994
Publication Information
Publication: Astrophysical Journal, Part 1
Volume: 433
Issue: 2
ISSN: 0004-637X
Subject Category
Astrophysics
Accession Number
95A72478
Funding Number(s)
CONTRACT_GRANT: NAG5-1409
CONTRACT_GRANT: NSF AST-89-18471
CONTRACT_GRANT: DFG-KU-474/13-1
CONTRACT_GRANT: NAG5-972
CONTRACT_GRANT: NSF AST-87-20530
CONTRACT_GRANT: DFG-KU-474/13-2
CONTRACT_GRANT: DFG-HU-424/1-1
CONTRACT_GRANT: DFG-HU-474/9-2
CONTRACT_GRANT: NSF AST-92-17961
Distribution Limits
Public
Copyright
Other

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