Observational Confirmation of a Link Between Common Envelope Binary Interaction and Planetary Nebula Shaping

TL;DR

This study provides observational evidence linking close binary star interactions to the shaping of planetary nebulae, supporting the hypothesis that binary dynamics influence nebular morphology.

Contribution

It extends previous work by adding two new systems, confirming the alignment between binary axes and nebular structures, and statistically demonstrating the binary-nebula shape connection.

Findings

Binary axes align with nebular symmetry axes.

Inclinations of binaries match nebulae orientations.

Updated orbital periods for NGC 6337 and Sp 1.

Abstract

A current issue in the study of planetary nebulae with close binary central stars is the extent to which the binaries affect the shaping of the nebulae. Recent studies have begun to show a high coincidence rate between nebulae with large-scale axial or point symmetries and close binary stars. In addition, combined binary-star and spatio-kinematic modeling of the nebulae have demonstrated that all of the systems studied to date appear to have their central binary axis aligned with the primary axis of the nebula. Here we add two more systems to the list, the central stars and nebulae of NGC 6337 and Sp 1. We show both systems to be low inclination, with their binary axis nearly aligned with our line-of-sight. Their inclinations match published values for the inclinations of their surrounding nebulae. Including these two systems with the existing sample statistically demonstrates a direct link between the central binary and the nebular morphology. In addition to the systems' inclinations we give ranges for other orbital parameters from binary modeling, including updated orbital periods for the binary central stars of NGC 6337 and Sp 1.