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Binaries and distances

Published online by Cambridge University Press:  26 February 2013

D. Pourbaix ,
F. Arenou ,
J.-L. Halbwachs  and
C. Siopis
D. Pourbaix
Affiliation:
F.R.S.–FNRS, 1000 Brussels, Belgium email: pourbaix@astro.ulb.ac.be Institut d'Astronomie et d'Astrophysique, Université Libre de Bruxelles (ULB), CP 226, Bld. du Triomphe, 1050 Brussels, Belgium
F. Arenou
Affiliation:
GEPI, Observatoire de Paris, CNRS, 92195 Meudon, France
J.-L. Halbwachs
Affiliation:
Observatoire Astronomique de Strasbourg, UMR 7550, 67000 Strasbourg, France
C. Siopis
Affiliation:
Institut d'Astronomie et d'Astrophysique, Université Libre de Bruxelles (ULB), CP 226, Bld. du Triomphe, 1050 Brussels, Belgium
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Abstract

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Gaia's five-year observation baseline might naively lead to the expectation that it will be possible to fit the parallax of any sufficiently nearby object with the default five-parameter model (position at a reference epoch, parallax and proper motion). However, simulated Gaia observations of a ‘model Universe’ composed of nearly 107 objects, 50% of which turn out to be multiple stars, show that the single-star hypothesis can severely affect parallax estimation and that more sophisticated models must be adopted. In principle, screening these spurious single-star solutions is rather straightforward, for example by evaluating the quality of the fits. However, the simulated Gaia observations also reveal that some seemingly acceptable single-star solutions can nonetheless lead to erroneous distances. These solutions turn out to be binaries with an orbital period close to one year. Without auxiliary (e.g., spectroscopic) data, they will remain unnoticed.

Keywords

astrometrybinaries: generalstars: distancesCepheids
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 8 , Symposium S289: Advancing the Physics of Cosmic Distances , August 2012 , pp. 70 - 73
Copyright
Copyright © International Astronomical Union 2013

References

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