Criss-cross mapping BD+30 3639: a new kinematic analysis technique

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We present a new analysis of kinematic data of the young planetary nebula BD+30 3639. The data include spectroscopic long-slit and internal proper motion measurements. In this paper we also introduce a new type of mapping of kinematic proper motion data that we name "criss-cross" mapping. It basically consists of finding all points where extended proper motion vectors cross converge. From the crossing points a map is generated which helps to interpret the kinematic data. From the criss-cross mapping of BD+30 3639, we conclude that the kinematic center is approximately 0.5 arcsec offset to the South-East from the central star. The mapping does also show evidence for a non-homologous expansion of the nebula that is consistent with a disturbance aligned with the bipolar molecular bullets.