A spectroscopic and photometric study of the planetary nebulae Kn 61 and Pa 5

TL;DR

This study provides the first detailed morpho-kinematical analysis of planetary nebulae Kn 61 and Pa 5, revealing their structures, kinematics, and central star characteristics, including potential binary presence and hydrogen deficiency.

Contribution

It offers the first morpho-kinematical analysis of Kn 61 and Pa 5, identifying their structures, kinematics, and central star properties, including a possible binary system and hydrogen deficiency.

Findings

Kn 61 is a spherical shell expanding at 67.6 km/s with a kinematic age of ~16,000 years.

Pa 5 has an equatorial toroid expanding at 45.2 km/s with faint polar extensions.

Kn 61's central star is a hydrogen-deficient PG 1159-type star.

Abstract

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 an 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 $\sim$ 1.6$\times$10$^4$ yrs for an assumed distance of 4 kpc. A photometric period of $\sim$ 5.7($\pm$0.4) days has been detected for Kn 61, indicating presence of a possible binary system at its core. A possible link between filamentary, spherical shells and PG 1159-type stars is noted. The morphology of Pa 5 is dominated by an equatorial toroid and faint polar extensions. The equatorial region of this planetary nebula is expanding at 45.2 kms$^{-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.