A morpho-kinematic view of the Necklace nebula

Abstract We present a morpho-kinematic study of the Necklace Nebula based on spatially resolved spectroscopic observations and 3D modeling performed with the shape software. The nebula is characterized by an equatorial disrupted ring accompanied by bipolar outflows. The geometry and velocity field of these different components are derived from the comparison between observed and synthetic images and position-velocity diagrams. The best model successfully reproduces the main morphological and kinematic features of the nebula, allowing us to constrain its 3D structure. We confirm that the disrupted ring is tilted about 60○ from the plane of the sky, but the bipolar outflows are inclined by 46○ with respect to the line of sight. This situation might indicate that the bipolar structures are not simple extensions of the equatorial ring, but instead correspond to a distinct mass-ejection event. The slight misalignment between these two components suggests either precession of the ejection axis, a temporal change in the dominant mass-loss geometry, or a misalignment in the magnetic field. Given that the Necklace Nebula hosts a close binary central star and is a well-established post-common envelope planetary nebula, our results support a scenario in which binary interaction plays a central role in shaping its morphology, even before the common envelope phase.