EDP Sciences
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Volume 397, Number 3, January III 2003
Page(s) L5 - L8
Section Letters
DOI http://dx.doi.org/10.1051/0004-6361:20021714

A&A 397, L5-L8 (2003)
DOI: 10.1051/0004-6361:20021714


First radius measurements of very low mass stars with the VLTI

D. Ségransan1, P. Kervella2, T. Forveille3, 4 and D. Queloz1

1  Observatoire de Genève, 51 chemin des maillettes, 1290 Sauverny, Switzerland
2  European Southern Observatory, Casilla 19001, Vitacura, Santiago 19, Chile
3  Observatoire de Grenoble, BP 53X, 38041 Grenoble Cedex, France
4  Canada-France-Hawaii Telescope Corporation, PO Box 1597, Kamuela, HI 96743, USA

(Received 15 October 2002 / Accepted 21 November 2002 )

We present 4 very low mass stars radii measured with the VLTI using the 2.2  $\mu$m VINCI test instrument. The observations were carried out during the commissioning of the 104-meter-baseline with two 8-meter-telescopes. We measure angular diameters of 0.7-1.5 mas with accuracies of 0.04-0.11 mas, and for spectral type ranging from M0V to M5.5V. We determine an empirical mass-radius relation for M dwarfs based on all available radius measurements. The observed relation agrees well with theoretical models at the present accuracy level, with possible discrepancy around 0.5-0.8  $M_{\odot}$ that needs to be confirmed. In the near future, dozens of M dwarfs radii will be measured with 0.1-1% accuracy, with the VLTI, thanks to the improvements expected from the near infrared instrument AMBER. This will bring strong observational constraints on both atmosphere and interior physics.

Key words: stars: low-mass, brown dwarfs -- stars: fundamental parameters -- techniques: interferometric

Offprint request: D. Ségransan, Damien.Segransan@obs.unige.ch

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