Journal
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
Volume 488, Issue 2, Pages 2864-2880Publisher
OXFORD UNIV PRESS
DOI: 10.1093/mnras/stz1848
Keywords
stars: abundances; stars: chemically peculiar; Galaxy: abundances; Galaxy: bulge; globular clusters: general; Galaxy: halo
Categories
Funding
- COST (European Cooperation in Science and Technology) [CA16117]
- FONDECYT [3180210]
- Physics Frontier Center/JINA Center for the Evolution of the Elements (JINA-CEE) - US National Science Foundation [PHY 14-30152]
- one-hundred-talent project of Sun Yat-Sen University
- Australian Research Council [DP180101791]
- UNSW Scientia Fellowship program
- Australian Research Council Centre of Excellence for All Sky Astrophysics in 3 Dimensions (ASTRO 3D) [CE170100013]
- FAPESP [2017/15893-1]
- DGAPAPAPIIT grant [IG100319]
- Region de Franche-Comte
- Institut des Sciences de l'Univers (INSU)
- Centre national d' etudes spatiales (CNES) [0101973]
- UTINAM Institute of the Universite de Franche-Comte - Region de Franche-Comte
- Alfred P. Sloan Foundation
- U.S. Department of Energy Office of Science
- Center for High-Performance Computing at the University of Utah
- Brazilian Participation Group
- Carnegie Institution for Science
- Carnegie Mellon University
- Chilean Participation Group
- French Participation Group
- Harvard-Smithsonian Center for Astrophysics
- Instituto de Astrofisica de Canarias
- Johns Hopkins University
- Kavli Institute for the Physics and Mathematics of the Universe (IPMU)/University of Tokyo
- Lawrence Berkeley National Laboratory
- Leibniz Institut fur Astrophysik Potsdam (AIP)
- Max-Planck-Institut fur Astronomie (MPIA Heidelberg)
- Max-Planck-Institut fur Astrophysik (MPA Garching)
- Max-Planck-Institut fur Extraterrestrische Physik (MPE)
- National Astronomical Observatory of China
- New Mexico StateUniversity
- New York University
- University of Dame
- Observatorio Nacional/MCTI
- Ohio State University
- Pennsylvania State University
- Shanghai Astronomical Observatory
- United Kingdom Participation Group
- Universidad Nacional Autonoma de Mexico
- University of Arizona
- University of Colorado Boulder
- University of Oxford
- University of Portsmouth
- University of Utah
- University of Virginia
- University of Washington
- University of Wisconsin
- Vanderbilt University
- Yale University
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The latest edition of the APOGEE-2/DR14 survey catalogue and the first Payne data release of APOGEE abundance determinations by Ting et al. are examined. We identify 31 previously unremarked metal-poor giant stars with anomalously high levels of [N/Fe] abundances, which is not usually observed among metal-poor stars in the Milky Way. We made use of the Brussels Automatic Stellar Parameter (BACCHUS) code to re-derive manually the chemical abundances of 31 field stars in order to compile the main element families, namely the light elements (C,N), a-elements (O, Mg, Si), iron-peak element (Fe), s-process elements (Ce, Nd), and the light odd-Z element (Na, Al). We have found all these objects have a [N/Fe] greater than or similar to +0.5, and are thus identified here as nitrogen-rich stars. An orbital analysis of these objects revealed that a handful of them shares the orbital properties of the bar/bulge, and possibly linked to tidal debris of surviving globular clusters trapped into the bar component. Three of the 31 stars are actually halo interlopers into the bulge area, which suggests that halo contamination is not insignificant when studying N-rich stars found in the inner Galaxy, whereas the rest of the N-rich stars share orbital properties with the halo population. Most of the newly identified population exhibits chemistry similar to the so-called second-generation globular cluster stars (enriched in aluminum, [Al/Fe] greater than or similar to +0.5), whereas a handful of them exhibit lower abundances of aluminum, [Al/Fe] < +0.5, which are thought to be chemically associated with the first generation of stars, as seen in globular clusters, or compatible with origin from a tidally disrupted dwarf galaxy.
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