On the dynamics of the AB Doradus system
1
Departamento de Astronomía y Astrofísica, Universidad de Valencia, 46100 Burjassot, Valencia, Spain e-mail: jose.c.guirado@uv.es
2
Steward Observatory, University of Arizona, Tucson, Arizona 85721, USA
3
Max-Planck Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany
4
Observatoire de Paris/LERMA, Rue de l'Observatoire 61, 75014 Paris, France
5
Australian Telescope National Facility, P.O. Box 76, Epping, NSW 2121, Australia
6
Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, California 91109, USA
Received:
4
July
2005
Accepted:
21
September
2005
We present an astrometric analysis of the binary systems
AB Dor A /AB Dor C and AB Dor Ba /AB Dor Bb. These two systems of
well-known late-type stars are gravitationally
associated and they constitute the quadruple AB Doradus system.
From the astrometric data available at different wavelengths,
we report:
(i) a determination of the orbit of AB Dor C,
the very low mass companion to AB Dor A, which confirms the mass estimate of
0.090 
reported in previous works;
(ii) a measurement of the parallax of AB Dor Ba, which unambiguously confirms the long-suspected physical association between this star and AB Dor A;
and (iii) evidence of orbital motion of AB Dor Ba around AB Dor A, which
places an upper bound of 0.4 on the mass of the pair
AB Dor Ba /AB Dor Bb (50% probability).
Further astrometric monitoring of the system at all possible
wavelengths would determine with extraordinary precision the dynamical mass
of its four components.
Key words: astrometry / stars: kinematics / stars: binaries: close / stars: late-type / stars: individual: Rst 137 B / stars: individual: AB Dor
© ESO, 2006