The GRAVITY young stellar object survey V. The orbit of the T Tauri binary star WW Cha
Abstract
The young T Tauri star WW Cha was recently proposed to be a close binary object with strong infrared and submillimeter excess associated with circum-system emission. This makes WW Cha a very interesting source for studying the influence of dynamical effects on circumstellar as well as circumbinary material. We derive the relative astrometric positions and flux ratios of the stellar companion in WW Cha from the interferometric model fitting of observations made with the VLTI instruments AMBER, PIONIER, and GRAVITY in the near-infrared from 2011 to 2020. For two epochs, the resulting uv-coverage in spatial frequencies permits us to perform the first image reconstruction of the system in the K band. The positions of nine epochs are used to determine the orbital elements and the total mass of the system. We find the secondary star orbiting the primary with a period of T=206.55 days, a semimajor axis of a=1.01 au, and a relatively high eccentricity of e=0.45. Combining the orbital solution with distance measurements from Gaia DR2 and the analysis of evolutionary tracks, the dynamical mass of Mtot=3.20 Msol can be explained by a mass ratio between ~0.5 and 1. The orbital angular momentum vector is in close alignment with the angular momentum vector of the outer disk as measured by ALMA and SPHERE. The analysis of the relative photometry suggests the presence of infrared excess surviving in the system and likely originating from truncated circumstellar disks. The flux ratio between the two components appears variable, in particular in the K band, and may hint at periods of triggered higher and lower accretion or changes in the disks' structures. The knowledge of the orbital parameters, combined with a relatively short period, makes WW Cha an ideal target for studying the interaction of a close young T Tauri binary with its surrounding material, such as time-dependent accretion phenomena.
Keywords
Cite
@article{arxiv.2102.00122,
title = {The GRAVITY young stellar object survey V. The orbit of the T Tauri binary star WW Cha},
author = {GRAVITY Collaboration and F. Eupen and L. Labadie and R. Grellmann and K. Perraut and W. Brandner and G. Duchêne and R. Köhler and J. Sanchez-Bermudez and R. Garcia Lopez and A. Caratti o Garatti and M. Benisty and C. Dougados and P. Garcia and L. Klarmann and A. Amorim and M. Bauböck and J. P. Berger and P. Caselli and Y. Clénet and V. Coudé du Foresto and P. T. de Zeeuw and A. Drescher and G. Duvert and A. Eckart and F. Eisenhauer and M. Filho and V. Ganci and F. Gao and E. Gendron and R. Genzel and S. Gillessen and G. Heissel and Th. Henning and S. Hippler and M. Horrobin and Z. Hubert and A. Jiménez-Rosales and L. Jocou and P. Kervella and S. Lacour and V. Lapeyrère and J. B. Le Bouquin and P. Léna and T. Ott and T. Paumard and G. Perrin and O. Pfuhl and G. Rodríguez-Coira and G. Rousset and S. Scheithauer and J. Shangguan and T. Shimizu and J. Stadler and O. Straub and C. Straubmeier and E. Sturm and E. van Dishoeck and F. Vincent and S. D. von Fellenberg and F. Widmann and J. Woillez and A. Wojtczak},
journal= {arXiv preprint arXiv:2102.00122},
year = {2021}
}
Comments
Accepted for publication in A&A; 24 pages, 14 figures, 3 tables; affiliations corrected