THE NATURE AND STRUCTURE OF THE EMISSION-LINE NEBULA K-3-35 - A VERY YOUNG PLANETARY-NEBULA WITH PRECESSING BIPOLAR JET-LIKE OUTFLOWS

We present H alpha, [N II]6583 and 6-cm continuum images of the emissi on line nebula K 3-35. The optical images reveal an extended nebula (s ize similar or equal to 11 x 9 arcsec(2) in [N II]) in which most of t he emission originates in a very narrow (width 0.7-1.3 arcsec) S-shape d region which extends almost all along the nebula (similar or equal t o 7 arcsec). The 6-cm continuum emission also arises in this narrow re gion, which is characterized by an exceedingly high point-symmetry and systematic and continuous changes of the orientation with respect to the nebular centre. The properties of the narrow region suggest that i t represents a system of precessing bipolar jet-like components. Two l ow-excitation, compact bipolar knots near the tips of the jet-like com ponents are observed in the deduced [N II]/H alpha image ratio. These knots may be generated by the interaction of the collimated outflows w ith surrounding material. A comparison of the optical and radio images shows the existence of differential extinction within the nebula. Max imum extinction is observed in a disc-like region which traces the equ ator of the elliptical shell previously observed at 20-cm continuum. A ll available data strongly suggest that K3-35 is a very young planetar y nebula in which we could be observing the first stages of the format ion of collimated outflows and point-symmetric structures typically ob served in planetary nebulae. The properties of the jet-like components in K3-35 are in good agreement with models of binary central stars in which highly collimated outflows originate either from a precessmg ac cretion disc or via magnetic collimation in a precessing star.