EDP Sciences
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Volume 425, Number 3, October III 2004
Page(s) L45 - L48
Section Letters
DOI http://dx.doi.org/10.1051/0004-6361:200400062

A&A 425, L45-L48 (2004)
DOI: 10.1051/0004-6361:200400062


A purely geometric distance to the binary star Atlas, a member of the Pleiades

N. Zwahlen1, P. North1, Y. Debernardi1, L. Eyer2, F. Galland3, M. A. T. Groenewegen4 and C. A. Hummel5

1  Laboratoire d'Astrophysique de l'EPFL, Observatoire, 1290 Chavannes-des-Bois, Switzerland
    e-mail: pierre.north@epfl.ch
2  Observatoire de Genève, 1290 Sauverny, Switzerland
3  Laboratoire d'Astrophysique, Observatoire de Grenoble, 38041 Grenoble Cedex 9, France
4  Instituut voor Sterrenkunde, KU Leuven, Celestijnenlaan 200B, 3001 Leuven, Belgium
5  European Southern Observatory, Casilla 19001, Santiago 19, Chile

(Received 19 July 2004 / Accepted 26 August 2004)

We present radial velocity and new interferometric measurements of the double star Atlas, which permit, with the addition of published interferometric data, to precisely derive the orbital parameters of the binary system and the masses of the components. The derived semi-major axis, compared with its measured angular size, allows to determine a distance to Atlas of $132\pm 4$ pc in a purely geometrical way. Under the assumption that the location of Atlas is representative of the average distance of the cluster, we confirm the distance value generally obtained through main sequence fitting, in contradiction with the early Hipparcos result ( $118.3\pm 3.5$ pc).

Key words: stars: individual: Atlas -- stars: distances -- stars: fundamental parameters -- Galaxy: open clusters and associations: individual: Pleiades

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© ESO 2004