Discovery of a Metal-Poor Field Giant with a Globular Cluster Second-Generation Abundance Pattern

We report on detection from observations obtained with the APOGEE spectroscopic survey of a metal poor ([Fe/H] =-1.3 dex) field giant star with an extreme Mg Al abundance ratio ([Mg/Fe] =-0.31 dex; [Al/Fe] =1.49 dex). Such low Mg/Al ratios are seen only among the second generation population of globular clusters and are not present among Galactic disk field stars. The light element abundances of this star 2M16011638 1201525 suggest that it could have been born in a globular cluster. We explore several origin scenarios in particular studying the orbit of the star to check the probability of it being kinematically related to known globular clusters. We performed simple orbital integrations assuming the estimated distance of 2M16011638 1201525 and the available six dimensional phase space coordinates of 63 globular clusters looking for close encounters in the past with a minimum distance approach within the tidal radius of each cluster. We found a very low probability that 2M16011638 1201525 was ejected from most globular clusters; however we note that the best progenitor candidate to host this star is globular cluster ? Centauri (NGC 5139). Our dynamical investigation demonstrates that 2M16011638 1201525 reaches a distance |Zmax