Bibcode
Fernández-Trincado, J. G.; Robin, A. C.; Moreno, E.; Schiavon, R. P.; García Pérez, A. E.; Vieira, K.; Cunha, K.; Zamora, O.; Sneden, C.; Souto, Diogo; Carrera, R.; Johnson, J. A.; Shetrone, M.; Zasowski, G.; García-Hernández, D. A.; Majewski, S. R.; Reylé, C.; Blanco-Cuaresma, S.; Martinez-Medina, L. A.; Pérez-Villegas, A.; Valenzuela, O.; Pichardo, B.; Meza, A.; Mészáros, Sz.; Sobeck, J.; Geisler, D.; Anders, F.; Schultheis, M.; Tang, B.; Roman-Lopes, A.; Mennickent, R. E.; Pan, K.; Nitschelm, C.; Allard, F.
Referencia bibliográfica
The Astrophysical Journal, Volume 833, Issue 2, article id. 132, 7 pp. (2016).
Fecha de publicación:
12
2016
Revista
Número de citas
66
Número de citas referidas
61
Descripción
We report on the detection, from observations obtained with the Apache
Point Observatory Galactic Evolution Experiment 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 (GCs) 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 GC. We
explore several origin scenarios, studying the orbit of the star in
particular to check the probability of its being kinematically related
to known GCs. We performed simple orbital integrations assuming the
estimated distance of 2M16011638-1201525 and the available
six-dimensional phase-space coordinates of 63 GCs, 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 GCs; however, we note that the
best progenitor candidate to host this star is GC ω Centauri (NGC
5139). Our dynamical investigation demonstrates that 2M16011638-1201525
reaches a distance | {Z}\max | \lt 3 {kpc} from the Galactic
plane and minimum and maximum approaches to the Galactic center of R
min < 0.62 kpc and R max < 7.26 kpc in an
eccentric (e ˜ 0.53) and retrograde orbit. Since the extreme
chemical anomaly of 2M16011638-1201525 has also been observed in halo
field stars, this object could also be considered a halo contaminant,
likely to have been ejected into the Milky Way disk from the halo. We
conclude that 2M16011638-20152 is also kinematically consistent with the
disk but chemically consistent with halo field stars.