Warm Gas in the Inner Disks around Young Intermediate‐Mass Stars

The characterization of gas in the inner disks around young stars is ofparticular interest because of its connection to planet formation. In order tostudy the gas in inner disks, we have obtained high-resolution K-band andM-band spectroscopy of 14 intermediate mass young stars. In sources that haveoptically thick inner disks, i.e. E(K-L)>1, our detection rate of thero-vibrational CO transitions is 100% and the gas is thermally excited. Of thefive sources that do not have optically thick inner disks, we only detect thero-vibrational CO transitions from HD 141569. In this case, we show that thegas is excited by UV fluorescence and that the inner disk is devoid of gas anddust. We discuss the plausibility of the various scenarios for forming thisinner hole. Our modeling of the UV fluoresced gas suggests an additional methodby which to search for and/or place stringent limits on gas in dust depletedregions in disks around Herbig Ae/Be stars.Comment: 42 pages, 16 figures, accepted by Ap