High-Resolution Imaging of Objects in the Post-AGB to Planetary Nebula Transition

We have obtained high-resolution images of two carbon-rich objects that are undergoing the transition from post-AGB star to planetary nebula: IRAS 21282+5050 (hereafter IRAS 21282), a young planetary nebula, and AFGL 3068, a post-AGB star with a high mass-loss rate. Detailed structure is seen in IRAS 21282. A torus of dust, with its polar axis in the N-S direction, surrounds the central star, impeding the wind in the E-W direction. This has caused the nebula to develop elongation in the N-S direction. Immediately surrounding the central star is a cavity where the dust has been cleared out. Beyond this cavity is the ionization front, which marks the extent of the ionized region. The presence of a shock front slightly farther out is suggested by linear emission. AFGL 3068 was observed in both infrared and optical wavelengths. Two different models are proposed to explain the presence of two point sources in the infrared images. The first hypothesis is that we are seeing a nebula surrounding the central star next to a reflection nebula. The second hypothesis is that the two point sources are two stars, which are responsible for the spiral structure seen in the optical wavelengths. Subject headings: post-AGB stars, pre-planetary nebulae, IRAS 21282+5050, AFGL 3068