Volume 505, Number 1, October I 2009
|Page(s)||205 - 215|
|Section||Stellar structure and evolution|
|Published online||24 July 2009|
Mass-radius relation of low and very low-mass stars revisited with the VLTI*
Observatoire de Genève, Université de Genève, 51 chemin des Maillettes, 1290 Sauverny, Suisse e-mail: Brice-Olivier.Demory@unige.ch
2 Laboratoire d'Astrophysique de Grenoble, 414 rue de la piscine, Domaine Universitaire de Saint Martin d'Hères, 38041 Grenoble, France
3 LESIA, Observatoire de Paris, CNRS UMR 8109, UPMC, Université Paris Diderot, 5 place Jules Janssen, 92195 Meudon, France
4 European Southern Observatory, Casilla 19001, Vitacura, Santiago 19, Chile
5 INAF-Osservatorio Astrofisico di Arcetri, Largo Fermi 5, 50125 Firenze, Italy
6 Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
7 Laboratoire Fizeau, UMR 6525 Observatoire de la Côte d'Azur, Boulevard de l'Observatoire, BP 4229, 06304 Nice Cedex 4, France
8 Laboratoire Fizeau, UMR 6525 Université de Nice-Sophia Antipolis, Parc Valrose, 06108 Nice Cedex 02, France
Accepted: 16 May 2009
We measured the radii of 7 low and very low-mass stars using long baseline interferometry with the VLTI interferometer and its VINCI and AMBER near-infrared recombiners. We use these new data, together with literature measurements, to examine the luminosity-radius and mass-radius relations for K and M dwarfs. The precision of the new interferometric radii now competes with what can be obtained for double-lined eclipsing binaries. Interferometry provides access to much less active stars, as well as to stars with much better measured distances and luminosities, and therefore complements the information obtained from eclipsing systems. The radii of magnetically quiet late-K to M dwarfs match the predictions of stellar evolution models very well, providing direct confirmation that magnetic activity explains the discrepancy that was recently found for magnetically active eclipsing systems. The radii of the early K dwarfs are reproduced well for a mixing length parameter that approaches the solar value, as qualitatively expected.
Key words: stars: low-mass, brown dwarfs / stars: fundamental parameters / techniques: interferometric
© ESO, 2009
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