On the dynamics of the AB Doradus system

• Published in: Astronomy and astrophysics (Berlin) Vol. 446; no. 2; pp. 733 - 738
• Main Authors: Guirado, J. C., Martí-Vidal, I., Marcaide, J. M., Close, L. M., Algaba, J. C., Brandner, W., Lestrade, J.-F., Jauncey, D. L., Jones, D. L., Preston, R. A., Reynolds, J. E.
• Format: Journal Article
• Language: English
• Published: Les Ulis EDP Sciences 01.02.2006
• Subjects: astrometry; Astronomy; Astrophysics; Earth, ocean, space; Exact sciences and technology; Physics; Sciences of the Universe; stars: binaries: close; stars: individual: AB Dor; stars: individual: Rst 137 B; stars: kinematics; stars: late-type; Late type stars; stars: binaries: close; stars: individual: Rst 137 B; Probability; Stellar kinematics; Astrometry; Upper bound; stars: kinematics; stars: late-type; Dynamics; Close binary stars; stars: individual: AB Dor; Orbit determination
• ISSN: 0004-6361; 1432-0746; 1432-0756
• DOI: 10.1051/0004-6361:20053757

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 $M_\odot$ 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 $M_\odot$ 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.