Physical Structure of Planetary Nebulae. II. NGC 7662
  We present a study of the structure and kinematics of the triple-shell planetary nebula NGC 7662 based on long-slit echelle spectroscopic observations and HST archival narrow-band images. The structure of NGC 7662 main nebula consists of a central cavity surrounded by two concentric shells. The bright inner shell has a non-negligible thickness and the highest density in the nebula. The outer shell is filled with nebular material whose density profile shows a propto 1/r drop-off in the inner regions of the shell and flattens in the outermost regions. Both the inner and the outer shells can be described as prolate ellipsoids: the inner shell is more elongated, while the outermost layer of the outer shell expands faster. The physical structure of NGC 7662 is qualitatively consistent with the predictions of hydrodynamical simulations based on the interacting-stellar-wind models for planetary nebulae with a 0.605 solar mass central star. Models with a higher AGB wind velocity are needed for detailed comparisons. 
Martin A. Guerrero (1,2), Elizabeth G. Jaxon (2), and You-Hua Chu (2)   ((1) Instituto de Astrofisica de Andalucia, CSIC, (2...