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A spectroscopic study of southern binary Cepheids

Published online by Cambridge University Press:  12 April 2016

O.K.L. Petterson ,
Michael D. Albrow ,
P.L. Cottrell  and
A. Fokin
O.K.L. Petterson
Affiliation:
Mount John University Observatory, Department of Physics and Astronomy, University of Canterbury, Private Bag 4800, Christchurch 8020, New Zealand
Michael D. Albrow
Affiliation:
Mount John University Observatory, Department of Physics and Astronomy, University of Canterbury, Private Bag 4800, Christchurch 8020, New Zealand
P.L. Cottrell
Affiliation:
Mount John University Observatory, Department of Physics and Astronomy, University of Canterbury, Private Bag 4800, Christchurch 8020, New Zealand
A. Fokin
Affiliation:
Institute of Astronomy, Russian Academy of Sciences, 48 Pjatnitskaja Str., 109017 Moscow, Russia

Abstract

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High-resolution spectroscopic observations have been made of a number of southern binary Cepheids to determine their dynamical masses. The stars are part of a long-term programme to observe southern variable stars for which a valuable long-term database has been obtained. The most recent radial velocities have a precision of ~300ms−1, allowing the detection of velocity differences of ~l kms−1 with confidence. Masses were determined for three systems: the 9-day Cepheid S Mus (6.0±0.4M⊙), the double-mode Cepheid Y Car (4.5±1.8M⊙) and the 5-day Cepheid V350Sgr (6.0±0.9M⊙). For five Cepheids (YZCar, AX Cir, V636 Sco, W Sgr and T Mon) new or improved orbital solutions were found. Line level effects have been observed in several species of lines. Most Cepheids were observed to show the same progression of line level effects. Using non-linear radiative hydrodynamical models, we have compared the results of these models with our observations. These have shown that AX Cir and YZ Car have the following properties: L = 2050 L⊙, M = 4.8 M), Teff = 5900 K and L = 9350 L∩, M = 7.7M∩, Teff = 5590 K. Our models show no strong Shockwaves being produced. Good agreement was found between the observed and modelled spectral lines Fe I 5576Å, Si II 6347Å, Ba II 5853Å and Ca II 8542Å.

Type
Part 6. Binary stars and pulsation
Information
International Astronomical Union Colloquium , Volume 193: Variable Stars in the Local Group , 2004 , pp. 403 - 406
Copyright
Copyright © Astronomical Society of the Pacific 2004

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