NGC 6778: a disrupted planetary nebula around a binary central star⋆
1 Instituto de Astrofísica de Andalucía (IAA-CSIC), Glorieta de la Astronomía, s/n, 18008 Granada, Spain
2 Consejo Superior de Investigaciones Científicas, c/ Serrano 117, 28006 Madrid, Spain
3 Departamento de Física Aplicada, Facultade de Ciencias, Campus Lagos-Marcosende s/n, Universidade de Vigo, 36310 Vigo, Spain
Received: 20 August 2011
Accepted: 12 January 2012
The planetary nebula (PN) NGC 6778 harbors a binary central star with a short orbital period and displays two systems of fast collimated outflows. To assess the influence of the evolution through a common-envelope phase of the binary system of NGC 6778 on its formation and shaping, we have used narrow-band images and high-dispersion long-slit spectra of the nebula to investigate its detailed morphology and kinematics. We find that the overall structure of NGC 6778 can be described as a bipolar PN. The equatorial ring is highly disrupted and many radial features (filamentary wisps and cometary knots) also show strong dynamical effects. There are clear connections between the bipolar lobes and the fast collimated outflows: the collimated outflows seem to arise from bright knots at the tips of the bipolar lobes, whereas the kinematics of the bipolar lobes is distorted. We suggest that the interaction of the fast collimated outflows of NGC 6778 with its nebular envelope has resulted in the disruption of the nebular shell and equatorial ring.
Key words: planetary nebulae: general / planetary nebulae: individual: NGC 6778 / ISM: jets and outflows / binaries: close
Based on observations made with the Nordic Optical Telescope (NOT) and the Italian Telescopio Nazionale Galileo (TNG) on the island of La Palma in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias (IAC). NOT is operated jointly by Denmark, Finland, Iceland, Norway, and Sweden. TNG is operated by the Fundación Galileo Galilei of the INAF (Istituto Nazionale di Astrofisica). The data presented here were obtained in part with ALFOSC, which is provided by the Instituto de Astrofísica de Andalucía (IAA) under a joint agreement with the University of Copenhagen and NOTSA.
© ESO, 2012