  (Abridged) Circumstellar disks are believed to be the birthplace of planets
and are expected to dissipate on a timescale of a few Myr. The processes
responsible for the removal of the dust and gas will strongly modify the radial
distribution of the dust and consequently the SED. In particular, a young
planet will open a gap, resulting in an inner disk dominating the near-IR
emission and an outer disk emitting mostly in the far-IR. We analyze a full set
of data (including VLTI/Pionier, VLTI/Midi, and VLT/NaCo/Sam) to constrain the
structure of the transition disk around TCha. We used the Mcfost radiative
transfer code to simultaneously model the SED and the interferometric
observations. We find that the dust responsible for the emission in excess in
the near-IR must have a narrow temperature distribution with a maximum close to
the silicate sublimation temperature. This translates into a narrow inner dusty
disk (0.07-0.11 AU). We find that the outer disk starts at about 12 AU and is
partially resolved by the Pionier, Sam, and Midi instruments. We show that the
Sam closure phases, interpreted as the signature of a candidate companion, may
actually trace the asymmetry generated by forward scattering by dust grains in
the upper layers of the outer disk. These observations help constrain the
inclination and position angle of the outer disk. The presence of matter inside
the gap is difficult to assess with present-day observations. Our model
suggests the outer disk contaminates the interferometric signature of any
potential companion that could be responsible for the gap opening, and such a
companion still has to be unambiguously detected. We stress the difficulty to
observe point sources in bright massive disks, and the consequent need to
account for disk asymmetries (e.g. anisotropic scattering) in model-dependent
search for companions.
