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.
@article{arxiv.astro-ph/0412514,
title = {Evidence for a hot dust-free inner disk around 51 Oph},
author = {W. -F. Thi and B. van Dalen and A. Bik and L. B. F. M. Waters},
journal= {arXiv preprint arXiv:astro-ph/0412514},
year = {2009}
}