  T Cha is a young star surrounded by a cold disk. The presence of a gap within
its disk, inferred from fitting to the spectral energy distribution, has
suggested on-going planetary formation. We observed T Cha in L' and K_s with
NAOS-CONICA, the adaptive optics system at the VLT, using sparse aperture
masking. We detected a source in the L' data at a separation of 62+-7 mas,
position angle of 78+-1 degrees, and a contrast of delta L' = 5.1+-0.2 mag. The
object is not detected in the Ks band data, which show a 3-sigma contrast limit
of 5.2 mag at the position of the detected L' source. For a distance of 108 pc,
the detected companion candidate is located at 6.7 AU from the primary, well
within the disk gap. If T Cha and the companion candidate are bound, the
comparison of the L' and Ks photometry with evolutionary tracks shows that the
photometry is inconsistent with any unextincted photosphere at the age and
distance of T Cha. The detected object shows a very red Ks-L' color for which a
possible explanation would be a significant amount of dust around it. This
would imply that the companion candidate is young, which would strengthen the
case for a physical companion, and moreover that the object would be in the
substellar regime, according to the Ks upper limit. Another exciting
possibility would be that this companion is a recently formed planet within the
disk. Additional observations are mandatory to confirm that the object is bound
and to properly characterize it.
