NEAR-INFRARED SPECTROSCOPY OF PROTOPLANETARY NEBULAE

Sixteen proto-planetary nebulae were observed with low-resolution infr ared spectroscopy in the H and K bands, and four were observed in the L band. In the H band, most of the objects show hydrogen Brackett line s (from n = 10-4 to n = 20-4) in absorption. In the K band, absorption bands (Delta v = 2) of CO were observed to as high as v = 6-4, and in three cases the CO bands are in emission. The CO spectrum of 22272+54 35 was found to change from emission to absorption over a 3 month inte rval. The CO emission most likely arises from collisional excitation r esulting from recent episodes of mass loss. One new object which possi bly shows weak 3.3 mu m emission was found.