AAOmega radial velocities rule out current membership of the planetary nebula NGC 2438 in the open cluster M46

We present new radial velocity measurements of 586 stars in a one-degree field centred on the open cluster M46, and the planetary nebula NGC 2438 located within a nuclear radius of the cluster. The data are based on medium-resolution optical and near-infrared spectra taken with the AAOmega spectrograph on the Anglo-Australian Telescope. We find a velocity difference of about 30 km s ^-1 between the cluster and nebula, thus removing all ambiguities about the cluster membership of the planetary nebula caused by contradicting results in the literature. The line-of-sight velocity dispersion of the cluster is 3.9 ± 0.3 km s^-1, likely to be affected by a significant population of binary stars.