The morphology and kinematics of the Fine Ring Nebula, planetary nebula Sp 1, and the shaping influence of its binary central star

TL;DR

This study provides the first detailed 3D model of the planetary nebula Sp 1, demonstrating how its binary central star influences its bipolar shape and revealing early interaction with the interstellar medium.

Contribution

It offers the first spatio-kinematical analysis linking the nebula's bipolar structure directly to the binary star system's orbital plane.

Findings

Sp 1 is a bipolar, axisymmetric nebula viewed nearly pole-on.

The nebula's symmetry axis is nearly perpendicular to the binary orbital plane.

Evidence of interaction with the interstellar medium through a bow-shock feature.

Abstract

We present the first detailed spatio-kinematical analysis and modelling of the planetary nebula Shapley 1 (Sp 1), which is known to contain a close-binary central star system. Close-binary central stars have been identified as a likely source of shaping in planetary nebulae, but with little observational support to date. Deep narrowband imaging in the light of [O III] {\lambda}5007A suggests the presence of a large bow-shock to the west of the nebula, indicating that it is undergoing the first stages of an interaction with the interstellar medium. Further narrowband imaging in the light of H{\alpha}+[NII] {\lambda}6584A combined with longslit observations of the H{\alpha} emission have been used to develop a spatio-kinematical model of Sp 1. The model clearly reveals Sp 1 to be a bipolar, axisymmetric structure viewed almost pole-on. The symmetry axis of the model nebula is within a few degrees of perpendicular to the orbital plane of the central binary system - strong evidence that the central close-binary system has played an important role in shaping the nebula. Sp 1 is one of very few nebulae to have this link, between nebular symmetry axis and binary plane, shown observationally.