Millimeter Observations of the disk around GW Ori
  The GW Ori system is a pre-main sequence triple system (GW Ori A/B/C) with
companions (GW Ori B/C) at $\sim$1 AU and $\sim$8 AU, respectively, from the
primary (GW Ori A). The primary of the system has a mass of 3.9 $M_{\odot}$,
but shows a spectral type of G8. Thus, GW Ori A could be a precursor of a B
star, but it is still at an earlier evolutionary stage than Herbig Be stars. GW
Ori provides us an ideal target for experiments and observations (being a
"blown-up" upscaled Solar System with a very massive "sun" and at least two
"upscaled planets"). We present the first spatially-resolved millimeter
interferometric observations of the disk around the triple pre-main-sequence
system GW Ori, obtained with the the Submillimeter Array, both in continuum and
in the $^{12}{\rm CO} J=2-1$, $^{13}{\rm CO} J=2-1$, and ${\rm C^{18}O} J=2-1$
lines. These new data reveal a huge, massive, and bright disk in the GW Ori
system. The dust continuum emission suggests a disk radius around 400 AU. But,
the $^{12}{\rm CO} J=2-1$ emission shows much more extended disk with a size
around 1300 AU. Due to the spatial resolution ($\sim$1$"$), we cannot detect
the gap in the disk which is inferred from spectral energy distribution (SED)
modeling. We characterize the dust and gas properties in the disk by comparing
the observations with the predictions from the disk models with various
parameters calculated with a Monte Carlo radiative transfer code RADMC-3D. The
disk mass is around 0.12 $M_{\odot}$, and the disk inclination with respect to
the line of sight is around $\sim$ 35$^\circ$. The kinematics in the disk
traced by the CO line emission strongly suggest that the circumstellar material
in the disk is in Keplerian rotation around GW Ori. Tentatively substantial
${\rm C^{18}O}$ depletion in gas phase is required to explain the
characteristics of the line emission from the disk.
