CO J = 3-2 and J = 2-1 observations of NGC 7027

The molecular envelope surrounding the planetary nebula NGC 7027 in the J = 3-2 line of (C-12)O is mapped and the central position in the J = 3-2 line of (C-13)O and the J = 2-1 lines of (C-12)O and (C-13)O is observed. The mass-loss rate along the nebula's polar axis is found to be about half that in the equatorial directions. Bright line wings are caused by a bipolar flow of molecular gas along the low-density axis. Bright line wings are caused by a bipolar flow of molecular gas along the low-density axis. It is argued that the marked asymmetry in the J = 3-2 line profile toward the central position is due to a radiative transfer effect. The data are compared with CO J = 1-0 observations, and new estimates are derived for envelope parameters from a detailed model. The kinetic temperature, total mass-loss rate, and CO:H2 abundance ratio are derived.