2007A&A...473..207P

We measure the mass and kinematics of the massive molecular torus in the the proto-typical butterfly planetary nebula NGC 6302. Determining the mass-loss history of the source is an important step in understanding the origin and formation of the wing-like morphology. Using the SMA interferometer we have imaged both the continuum emission and the J=2-1 transitions of ¹²CO and ¹³CO at arcsecond resolution. These data are analysed in combination with observations of both the J=2-1 and J=3-2 transitions of ¹²CO and ¹³CO made with JCMT. The ¹²CO and ¹³CO emission match the dark lane seen in absorption in the Hα image of the object and trace an expanding torus of material. The CO indicates a mass of the torus of ∼2M_☉±1 M_☉. The torus is expanding with a velocity of ∼8km/s, centred at V_lsr=-31.5km/s. The size and expansion velocity of the torus indicates that it was ejected from ∼7500yr to 2900yr ago, with a mass-loss rate of 5x10^–4M_☉/yr. In addition we detect a ballistic component in the CO images which has a velocity gradient of 140km/s/pc. The derived mass-loss history of the torus favours binary interaction as the cause of the ejection of the torus and we predict the existence of a companion with an orbital period P≲1month.