A SPECTROSCOPIC AND PHOTOMETRIC STUDY OF THE PLANETARY NEBULAE Kn?61 AND Pa?5

摘要

We present the first morpho-kinematical analysis of the planetary nebulae Kn?61 and Pa?5 and explore the nature of their central stars. Our analysis is based on high-resolution and medium-resolution spectroscopic observations, deep narrow-band imaging, and integral photometry. This material allows us to identify the morphological components and study their kinematics. The direct images and spectra indicate an absence of the characteristic [N II] and [S II] emission lines in both nebulae. The nebular spectrum of Kn?61 suggests a hydrogen deficient planetary nebula and the stellar spectrum of the central star reveals a hydrogen-deficient PG 1159-type star. The [O III] position velocity diagram reveals that Kn?61 is a closed, empty, spherical shell with a thin border and a filamentary surface expanding at 67.6 km s–1 and the shell is currently not expanding isotropically. We derived a kinematic age of ~1.6?×?104 yr for an assumed distance of 4 kpc. A photometric period of ~5.7(±0.4) days has been detected for Kn?61, indicating the presence of a possible binary system at its core. A possible link between filamentary spherical shells and PG 1159-type stars is noted. The morphology of Pa?5 is dominated by an equatorial toroid and faint polar extensions. The equatorial region of this planetary nebula is expanding at 45.2 km s–1. The stellar spectrum corresponds to a very hot star and is dominated by a steep blue rising continuum and He II, Balmer, and Ca II photospheric lines.