The size of AB Doradus A from VLTI/AMBER interferometry^⋆

¹ Dpto. Astronomía y Astrofísica, Universidad de Valencia, Dr. Moliner 50, 46100 Burjassot, Valencia, Spain
e-mail: guirado@uv.es
² Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
³ Laboratoire d’Astrophysique de Grenoble, CNRS-UJF UMR 5571, 414 rue de la Piscine, 38400 Saint Martin d’Hères, France
⁴ Steward Observatory, University of Arizona, Tucson, Arizona 85721, USA
⁵ National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903-2475, USA
⁶ Institut d’Astrophysique et de Gèophysique de l’Université de Liège, Allée du 6 Août 17, 4000 Liège, Belgium

Received: 7 June 2011
Accepted: 4 August 2011

Abstract

The pre-main sequence (PMS) star AB Dor A is the main component of the quadruple system AB Doradus. The precise determination of the mass and photometry of the close companion to AB Dor A, AB Dor C, has provided an important benchmark for calibration of theoretical evolutionary models of low-mass stars. The limiting factor to the precision of this calibration is the age of the system, as both the mass and luminosity of AB Dor A and C are well monitored by other ongoing programs. In this paper we present VLTI/AMBER observations of AB Dor A which provide a direct measurement of the size of this star, 0.96 ± 0.06 R_⊙. The latter estimate, combined with other fundamental parameters also measured for this star, allows a precise test of PMS evolutionary models using both H-R diagrams and mass-radius relationships. We have found that our radius measurement is larger than that predicted by the models, which we interpret as an evidence of the oversizing produced by the strong magnetic activity of AB Dor A. Considering, at least partially, this magnetic effect, theoretical isochrones have been used to derive constraints to the age of AB Dor A, favouring an age about 40–50 Myr for this system. Older ages are not completely excluded by our data.