Excitation analysis of SO and SO2 in the proto-planetary nebula OH 231.8+4.2

In the nebula OH 231.8+4.2 we have observed SO and SO2 millimeter-wave emis sion lines having a SO2 wide range of excitation energy. The extent of the SO emission was also mapped. Rotation diagrams were derived from these obse rvations, and we deduced the rotation temperatures and relative abundances of SO and SO2 for three different velocity ranges corresponding to the sphe rical mass-loss envelope and the blue and red lobes of the bipolar outflow. The rotation temperatures for SO and SO2 are higher in the expanding envel ope than in the outflow lobes. Subject to modeling uncertainties, the relat ive abundances of both molecules in the lobes are slightly enhanced by fact ors 2-5 times relative to the values in the envelope.