Millimeter observations of the disk around GW Orionis

The GW Ori system is a pre-main sequence triple system (GW Ori A/B/C) with companions (GW Ori B/C) at ~1 AU and ~8 AU, respectively, from the primary (GW Ori A). The primary of the system has a mass of 3.9 M_?, 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 an ideal target for experiments and observations (being a "blown-up" 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 Submillimeter Array, both in continuum and in the ¹²CO J = 2-1, ¹³CO J = 2-1, and C¹⁸O 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 of around 400 AU, but the ¹²CO J = 2-1 emission shows a much more extended disk with a size around 1300 AU. Owing to the spatial resolution (~1′′), we cannot detect the gap in the disk that 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 around0.12 M_?, and the disk inclination with respect to the line of sight is around ~35°. 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 C¹⁸O depletion in gas phase is required to explain the characteristics of the line emission from the disk.