  We report high spectral resolution observations of the CO vibrational
overtone emission from the young stellar object 1548C27; our observations
include both the CO(2-0) and CO(5-3) bandhead regions. These data and similar
observations of the young stellar object WL16, reported in a previous
contribution to this journal, provide some of the most compelling evidence to
date for the existence of inner disks around young stars. We describe the
simple procedure that we use to synthesize bandhead emission from disks
including the effect of thermal dissociation of CO and non-LTE excitation of
the vibrational levels. Using this spectral synthesis procedure to extract the
kinematics and physical properties of the emitting gas from the overtone data,
we show how these high signal-to-noise data are also powerful probes of the
stellar and inner disk properties of these systems. Our modeling is consistent
with the identification of WL16 and 1548C27 as Herbig AeBe stars with stellar
masses of approximately 2 and 4 solar masses, respectively. Thus, the kinematic
signature of rotating disks in the overtone spectra of these sources provides
strong support for the role of accretion disks in the formation of intermediate
mass stars. For both WL16 and 1548C27, we interpret our modeling results as
indicating that the overtone emission arises from a temperature inversion
region in the inner disk atmosphere. We also find evidence for suprathermally
broadened lines and are able to place useful constraints on the radial
temperature and column density distributions of the CO line-formation region of
the disk atmosphere.
