  We report on the observation of CO bandhead emission around 51 Oph (dv=2). A
high resolving power (R~10,000) spectrum was obtained with the infrared
spectrometer ISAAC mounted on VLT-ANTU. Modeling of the profile suggests that
the hot (Tgas=2000-4000K) and dense (n_H>1e10 cm-3) molecular material as
probed by the CO bandhead is located in the inner AU of a Keplerian disk viewed
almost edge-on. Combined with the observation of cooler gas (Tgas=500-900K) by
ISO-SWS and the lack of cold material, our data suggest that the disk around 51
Oph is essentially warm and small. We demonstrate the presence of a dust-free
inner disk that extents from the inner truncation radius until the dust
sublimation radius. The disk around 51 Oph may be in a rare transition state
toward a small debris disk object.
