1994A&A...286..149D

Interferometric ¹³CO J=1->0 observations performed with the IRAM interferometer reveal unambiguously a fully resolved rotating thin disk around the young close binary system GG Tau. The rotation curve and geometrical aspect are in perfect agreement with a Keplerian disk orbiting a binary system with total mass ≃ 1.2 M_☉, consistent with the luminosities of the central stars, and inclined ∼43deg to the line of sight. Images of the dust continuum emission show that the disk has a large inner cavity, of radius ∼180 AU. The disk extends at least to an outer radius ∼800 AU. The continuum dust emission and ¹³CO and C¹⁸O line fluxes taken together imply that the CO abundance in the disk is lower than that typical of the ISM by at least a factor of ∼20. Tidal forces induced by the binary are probably responsible for the inner hole in the dust and gas distribution. The size of the inner cavity is most simply explained if the orbit of the binary is eccentric. In such a case, the dust ring is located near an orbital resonance of the disk with the binary period. Effective angular momentum transfer from the binary to the disk is expected to increase the orbital eccentricity, and to stop further accretion onto the stars, thereby increasing the lifetime of the circumbinary disk.