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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., Comment: Accepted for publication in A&A; 24 pages, 14 figures, 3 tables; affiliations corrected

We present Submillimeter-Array (SMA) observations of two embedded young stellar objects, Elias 29 and IRS 63. The masses of the central stars, the discs, and the envelopes are determined for such young objects for the first time. A survey of bright T-Tauri stars in the southern constellations Lupus and Chamaeleon was carried out with the Australia Telescope Compact Array (ATCA) at 3 mm. The Lupus sources were subsequently observed with the SMA at 1 mm. Comparison with the 10-micron silicate features of seven of the sources suggested a correlation between the infrared and radio data. A large survey of T-Tauri stars was carried out with the SMA, the ATCA, the Combined Array for Research in Millimeter-wave Astronomy (CARMA), and the Very Large Array (VLA). The correlation between the infrared and radio data was confirmed, suggesting that planet formation in discs is more uniform then heretofore thought. Three bright T-Tauri stars were followed up with the ATCA at 7 mm, 1.6, 3.5, and 6.3 cm. Dust emission up to 7 mm was detected around CS Cha and RU Lup and even up to 1.6 cm for WW Cha, indicating that grains have grown up to sizes of at least several centimetres.