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 \simeq 0 \aas@@fstack { \prime \prime } 021 ( \simeq 100 AU ) radius , observed with an inclination angle with respect to the line of sight of 55 \degr .
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 PA \simeq 158 \degr , 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 .