Chemodynamical evidence of the HR 1614 moving group as a bar resonance

Moving groups (MGs) are ensembles of disk stars that clump in velocity and action space. A multitude of explanations as to their origin has been attempted, from dissolved star clusters, to resonances with the Galactic bar, or other non-axisymmetric perturbations. The object of this work, the old HR 1614 group, has already been shown not to be a disrupted cluster in terms of its broad age and metallicity distribution. Thus, its stars have more likely been trapped by the Milky Way bar at corotation . Here, we present a new study that aims to chemically and dynamically characterize this group in the context of such a resonance . To this end, we used MIKE/Magellan high-resolution, high signal-to-noise spectra of six member stars of the HR 1614 MG to determine the chemical abundance ratios for 24 elements, several for the first time in those stars. The Fe-abundances of our sample range from +0.13 to 0.38 dex and the majority of abundance ratios are fully in line with those of metal-rich Milky Way disk stars, with few exceptions. In particular, the group's eponym, HR 1614, is enhanced in essentially all abundances and coincides with the higher- X/Fe trends of the Milky Way's thick disk. All elements (except S and Ca) show significant intrinsic abundance scatter that argues against this MG having formed in a contained environment such as a dissolved cluster. Isochrone ages, tailored to measured metallicities, support earlier findings of a broad age mix in this group, ranging from ∼1 Gyr to as old as ∼8 Gyr. We performed an orbital frequency analysis in a Galactic potential that includes a rotating bar. Indeed, our sample stars fall onto thin resonances on corotation. Hence, our results support the idea that the HR 1614 MG is a resonantly perturbed disk feature, mustering a mélange of stars from different parent populations in the inner Galaxy.