Volume 558, October 2013
|Number of page(s)||8|
|Section||Stellar structure and evolution|
|Published online||07 October 2013|
Orbits and masses in the young triple system TWA 5 ⋆
Max-Planck-Institut für Astronomie, Königstuhl 17, 69117
2 Universitäts-Sternwarte München, Ludwig-Maximilians-Universität, Scheinerstr. 1, 81679 München, Germany
3 European Southern Observatory, Karl-Schwarzschild-Str. 2, 85748 Garching bei München, Germany
4 Institute for Astronomy, University of Hawaii, 34 Ohia Ku Str., Pukalani, HI 96768, USA
Received: 15 October 2012
Accepted: 25 August 2013
Aims. We aim to improve the orbital elements and determine the individual masses of the components in the triple system TWA 5.
Methods. Five new relative astrometric positions in the H band were recorded with the adaptive optics system at the Very Large Telescope (VLT). We combine them with data from the literature and a measurement in the Ks band. We derive an improved fit for the orbit of TWA 5Aa-b around each other. Furthermore, we use the third component, TWA 5B, as an astrometric reference to determine the motion of Aa and Ab around their center of mass and compute their mass ratio.
Results. We find an orbital period of 6.03 ± 0.01 years and a semi-major axis of 63.7 ± 0.2 mas (3.2 ± 0.1 AU). With the trigonometric distance of 50.1 ± 1.8 pc, this yields a system mass of 0.9 ± 0.1 M⊙, where the error is dominated by the error of the distance. The dynamical mass agrees with the system mass predicted by a number of theoretical models if we assume that TWA5 is at the young end of the age range of the TW Hydrae association. We find a mass ratio of MAb/MAa = 1.3-0.4+0.6 , where the less luminous component Ab is more massive. This result is likely to be a consequence of the large uncertainties due to the limited orbital coverage of the observations.
Key words: stars: low-mass / brown dwarfs / stars: fundamental parameters / stars: individual: TWA 5 / binaries: close / celestial mechanics
© ESO, 2013
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.