Spatially resolved mid-infrared observations of the triple system T?Tauri

摘要

Aims. The aim of this study is to enhance our knowledge of the characteristics and distribution of the circumstellar dust associated with the individual components of the young hierarchical triple system TTau. Methods. To reach this goal, observations in the N-band (8-13m) with the two-telescope interferometric instrument MIDI at the VLTI were performed. For the northern component of the TTau system, projected baseline lengths of 43m, 62m, and 85m were used. For the southern binary projected baseline lengths of equivalent resolution could be utilised. Our study is based on both theinterferometric and the spectrophotometric measurements and is supplemented by new visual and infrared photometry. Also,the phases were investigated to determine the dominating mid-infrared source in the close southern binary. The data were fit with thehelp of a sophisticated physical disc model. This model utilises the radiative transfer code MC3D that is based on the Monte-Carlo method. Results. Extended mid-infrared emission is found around all three components of the system. Simultaneous fits to the photometric and interferometric data confirm the picture of an almost face-on circumstellar disc around TTauN. Towards this star, the silicate band is seen in emission. This emission feature is used to model the dust content of the circumstellar disc. Clear signs of dust processing are found. Towards TTauS, the silicate band is seen in absorption. This absorption is strongly pronounced towards the infrared companion TTauSa as can be seen from the first individual N-band spectra for the two southern components. Our fits support the previous suggestion that an almost edge-on disc is present around TTauSa. This disc is thus misaligned with respect to the circumstellar disc around TTauN. The interferometric data indicate that the disc around TTauSa is oriented in the north-south direction, which favours this source as launching site for the east-western jet. We further determine from the interferometric data the relative positions of the components of the southern binary in the N-band. We find good agreement with recent position measurements in the near-infrared. Key words: stars: individual: TTauri - circumstellar matter - stars: pre-main sequence - techniques: interferometric - infrared: stars