Kinematics of the H2O masers at the centre of the planetary nebula K3–35.

We have studied the kinematics traced by the water masers located at the centre of the planetary nebula (PN) K3–35, using data from previous Very Large Array (VLA) observations. An analysis of the spatial distribution and line-of-sight velocities of the maser spots allows us to identify typical patterns of a rotating and expanding ring in the position–velocity diagrams, according to our kinematical model. We find that the distribution of the masers is compatible with tracing a circular ring with a ≃0.021-arcsec (≃100-au) radius, observed with an inclination angle of 55° with respect to the line of sight. We derive expansion and rotation velocities of 1.4 and 3.1 km s⁻¹, respectively. The orientation of the ring, projected on the plane of the sky, at , is almost orthogonal to the direction of the innermost region of the jet observed in K3–35, suggesting the presence of a disc or torus that may be related to the collimation of the outflow. [ABSTRACT FROM AUTHOR]