We present deep Sparse Aperture Masking ( SAM ) observations obtained with the ESO Very Large Telescope of the pre-transitional disk object FL Cha ( SpT=K8 , d=160 pc ) , the disk of which is known to have a wide optically thin gap separating optically thick inner and outer disk components .
We find non-zero closure phases , indicating a significant flux asymmetry in the K _ { S } -band emission ( e.g. , a departure from a single point source detection ) .
We also present radiative transfer modeling of the SED of the FL Cha system and find that the gap extends from 0.06 _ { -0.01 } ^ { +0.05 } AU to 8.3 \pm 1.3 AU .
We demonstrate that the non-zero closure phases can be explained almost equally well by starlight scattered off the inner edge of the outer disk or by a ( sub ) stellar companion .
Single-epoch , single-wavelength SAM observations of transitional disks with large cavities that could become resolved should thus be interpreted with caution , taking the disk and its properties into consideration .
In the context of a binary model , the signal is most consistent with a high-contrast ( \Delta K _ { S } \sim 4.8 mag ) source at a \sim 40 mas ( 6 AU ) projected separation .
However , the flux ratio and separation parameters remain highly degenerate and a much brighter source ( \Delta K _ { S } \sim 1 mag ) at 15 mas ( 2.4 AU ) can also reproduce the signal .
Second-epoch , multi-wavelength observations are needed to establish the nature of the SAM detection in FL Cha .