1996A&A...312..560A

We present ¹²CO and ¹³CO microwave line observations of the protoplanetary nebula OH 231.8+4.2. The extent of the emission is comparable to the optical nebula, the CO lines showing a large total range of observed velocity that exceeds 300km/s. The velocity of the molecular gas shows a very strong and well defined gradient along the nebular axis. In the south lobe, coincident with the bow-shaped structure identified in optical images, we detect an extension of the CO nebula which has no counterpart in the north. In this region, the CO emitting gas is flowing in the axial direction with (deprojected) velocities up to 330km/s. The total mass probed by CO is large, ∼0.5-1M_☉, probably being the dominant component of the nebular material. A mass of at least 0.1M_☉ is found to be in axial expansion at more than 30km/s. It is argued that this massive fast wind is the remnant of the past AGB mass loss process, accelerated by the presently active bipolar ejections. Mass and momentum (in the axial direction) are calculated for the different spectral features. We estimate that the kinematic time needed to shape the present nebula (from the AGB precursor) is ∼900yr.