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Fundamental Parameters of the W Serpentis Stars

Published online by Cambridge University Press:  12 April 2016

J. Andersen
Affiliation:
Copenhagen University Observatory, Denmark, andHarvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, U.S.A.
B. Nordström
Affiliation:
Copenhagen University Observatory, Denmark, andHarvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, U.S.A.

Abstract

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Application of digital cross-correlation spectroscopy to the spectra of the W Serpentis binaries SX Cas and RX Cas has allowed an accurate determination of the orbits and rotations of the (mass-losing) K-subgiant secondary components. The distortion of the primary radial-velocity curves due to the influence of the prominent accretion disks in these systems has been modelled to first order. This enables us to estimate K1 , and thereby the mass ratio q ≈ 0.30, to within ~±20%. The absolute radii of the secondaries are derived independently from the observed rotations and periods, assuming synchronous rotation. They show that the stars fill their Roche lobes, or at least very nearly so. Rough fits to the available photometry shows both primaries to be unevolved mid-B stars; that in RX Cas appears completely obscured by the disk. Preliminary spectroscopic data for W Ser and W Cru show some promise for similar analyses of these systems.

Type
Research Article
Copyright
Copyright © Kluwer 1989

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