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

Journal article, 2012

We present the first detailed spatiokinematical 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 narrow-band imaging in the light of [O III] λ5007Å 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 narrow-band imaging in the light of Hα + [N II] λ6584Å combined with long-slit observations of the Hα emission have been used to develop a spatiokinematical 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 the very few nebulae to have this link, between nebular symmetry axis and binary plane, shown observationally.