Dynamical masses of the low-mass stellar binary AB Doradus B
Artikel i vetenskaplig tidskrift, 2015

Context. AB Doradus is the main system of the AB Doradus moving group. It is a quadruple system formed by two widely separated binaries of pre-main-sequence (PMS) stars: AB Dor A/C and AB Dor Ba/Bb. The pair AB Dor A/C has been extensively studied and its dynamical masses have been determined with high precision, thus making AB Dor C a benchmark for calibrating PMS stellar models. If the orbit and dynamical masses of the pair AB Dor Ba/Bb could be determined, they could play a similar role to that of AB Dor C in calibrating PMS models, and would also help to better understand the dynamics of the whole AB Doradus system. Aims. We aim to determine the individual masses of the pair AB Dor Ba/Bb using VLBI observations and archive infrared data as part of a larger program that monitors binary systems in the AB Doradus moving group. Methods. We observed the system AB Dor B between 2007 and 2013 with the Australian Long Baseline Array (LBA) at a frequency of 8.4 GHz in phase-reference mode. Results. We detected, for the first time, compact radio emission from both stars in the binary, AB Dor Ba and AB Dor Bb. This result allowed us to determine the orbital parameters of both the relative and absolute orbits and, consequently, their individual dynamical masses: 0.28 ± 0.05 M ⊙ and 0.25 ± 0.05 M ⊙ , respectively. Conclusions. Comparisons of the dynamical masses with the prediction of PMS evolutionary models show that the models underpredict the dynamical masses of the binary components Ba and Bb by 10-30% and 10-40%, respectively, although they still agree at the 2σ level. Some of the stellar models considered favor an age between 50 and 100 Myr for this system, while others predict older ages. We also discuss the evolutionary status of AB Dor Ba/Bb in terms of an earlier double-double star scenario that might explain the strong radio emission detected in both components.


Stars: pre-main sequence

Stars: fundamental parameters

Binaries: close


R. Azulay

Universitat de Valencia

Max Planck-institutet

J. C. Guirado

Universitat de Valencia

J.M. Marcaide

Universitat de Valencia

Ivan Marti-Vidal

Chalmers, Rymd- och geovetenskap, Onsala rymdobservatorium

Eduardo Ros

Max Planck-institutet

Universitat de Valencia

D.L. Jauncey

CSIRO Astronomy and Space Science

Australian National University

J.F. Lestrade

LERMA - Laboratoire d'Etudes du Rayonnement et de la Matiere en Astrophysique et Atmospheres

R.A. Preston

Jet Propulsion Laboratory, California Institute of Technology

J.E. Reynolds

CSIRO Astronomy and Space Science

E. Tognelli

Universita degli Studi di Roma Tor Vergata

Istituto Nazionale Di Fisica Nucleare, Frascati

P. Ventura

Istituto Nazionale Di Astrofisica, Rome

Astronomy and Astrophysics

0004-6361 (ISSN) 1432-0746 (eISSN)

Vol. 578 Art. no. A16- A16


Astronomi, astrofysik och kosmologi