[en] We report the discovery of a group of apparently young CoRoT red-giant stars exhibiting enhanced [α/Fe] abundance ratios (as determined from APOGEE spectra) with respect to solar values. Their existence is not explained bystandard chemical evolution models of the Milky Way, and shows that the chemical-enrichment history of the Galactic disc is more complex. We find similar stars in previously published samples for which isochrone-ages could be reliably obtained, although in smaller relative numbers. This might explain why these stars have not previously received attention. The young [α/Fe]-rich stars are much more numerous in the CoRoT-APOGEE (CoRoGEE) inner-field sample than in any other high-resolution sample available at present because only CoRoGEE can explore the inner-disc regions and provide ages for its field stars. The kinematic properties of the young [α/Fe]-rich stars are not clearly thick-disc like, despite their rather large distances from the Galactic mid-plane. Our tentative interpretation of these and previous intriguing observations in the Milky Way is that these stars were formed close to the end of the Galactic bar, near corotation - a region where gas can be kept inert for longer times than in other regions that are more frequently shocked by the passage of spiral arms. Moreover, this is where the mass return from older inner-disc stellar generations is expected to be highest (according to an inside-out disc-formation scenario), which additionally dilutes the in-situ gas. Other possibilities to explain these observations (e.g., a recent gas-accretion event) are also discussed. Appendix A is available in electronic form at <A href="http://www.aanda.org/10.1051/0004-6361/201525865/olm">http://www.aanda.org</A>
Disciplines :
Space science, astronomy & astrophysics
Author, co-author :
Chiappini, C.; Leibniz-Institut für Astrophysik Potsdam (AIP), An der Sternwarte 16, 14482, Potsdam, Germany ; Laboratório Interinstitucional de e-Astronomia, - LIneA, Rua Gal. José Cristino 77, 20921-400, Rio de Janeiro, Brazil
Anders, F.; Leibniz-Institut für Astrophysik Potsdam (AIP), An der Sternwarte 16, 14482, Potsdam, Germany ; Laboratório Interinstitucional de e-Astronomia, - LIneA, Rua Gal. José Cristino 77, 20921-400, Rio de Janeiro, Brazil
Rodrigues, T. S.; Laboratório Interinstitucional de e-Astronomia, - LIneA, Rua Gal. José Cristino 77, 20921-400, Rio de Janeiro, Brazil ; Osservatorio Astronomico di Padova - INAF, Vicolo dell'Osservatorio 5, 35122, Padova, Italy ; Dipartimento di Fisica e Astronomia, Università di Padova, Vicolo dell'Osservatorio 3, 35122, Padova, Italy
Miglio, A.; School of Physics and Astronomy, University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK
Montalbán, J.; Dipartimento di Fisica e Astronomia, Università di Padova, Vicolo dell'Osservatorio 3, 35122, Padova, Italy
Mosser, B.; LESIA, Université Pierre et Marie Curie, Université Denis Diderot, Obs. de Paris, 92195, Meudon Cedex, France
Girardi, L.; Laboratório Interinstitucional de e-Astronomia, - LIneA, Rua Gal. José Cristino 77, 20921-400, Rio de Janeiro, Brazil ; Osservatorio Astronomico di Padova - INAF, Vicolo dell'Osservatorio 5, 35122, Padova, Italy
Valentini, Marica ; Leibniz-Institut für Astrophysik Potsdam (AIP), An der Sternwarte 16, 14482, Potsdam, Germany
Noels-Grötsch, Arlette ; Université de Liège > Département d'astrophys., géophysique et océanographie (AGO) > Département d'astrophys., géophysique et océanographie (AGO)
Morel, Thierry ; Université de Liège > Groupe d'astrophysique des hautes énergies (GAPHE)
Minchev, I.; Leibniz-Institut für Astrophysik Potsdam (AIP), An der Sternwarte 16, 14482, Potsdam, Germany
Steinmetz, M.; Leibniz-Institut für Astrophysik Potsdam (AIP), An der Sternwarte 16, 14482, Potsdam, Germany
Santiago, B. X.; Laboratório Interinstitucional de e-Astronomia, - LIneA, Rua Gal. José Cristino 77, 20921-400, Rio de Janeiro, Brazil ; Instituto de Física, Universidade Federal do Rio Grande do Sul, Caixa Postal 15051, 91501-970, Porto Alegre, Brazil
Schultheis, M.; Observatoire de la Côte d'Azur, Laboratoire Lagrange, CNRS UMR 7923, BP 4229, 06304, Nice Cedex, France
Martig, M.; Max-Planck-Institut für Astronomie, Königstuhl 17, 69117, Heidelberg, Germany
da Costa, L. N.; Laboratório Interinstitucional de e-Astronomia, - LIneA, Rua Gal. José Cristino 77, 20921-400, Rio de Janeiro, Brazil ; Observatório Nacional, Rua Gal. José Cristino 77, 20921-400, Rio de Janeiro, Brazil
Maia, M. A. G.; Laboratório Interinstitucional de e-Astronomia, - LIneA, Rua Gal. José Cristino 77, 20921-400, Rio de Janeiro, Brazil ; Observatório Nacional, Rua Gal. José Cristino 77, 20921-400, Rio de Janeiro, Brazil
Allende Prieto, C.; Instituto de Astrofísica de Canarias, 38205, La Laguna, Tenerife, Spain ; Universidad de La Laguna, Departamento de Astrofísica, 38206, La Laguna, Tenerife, Spain
de Assis Peralta, R.; LESIA, Université Pierre et Marie Curie, Université Denis Diderot, Obs. de Paris, 92195, Meudon Cedex, France
Hekker, S.; Max-Planck-Institut für Sonnensystemforschung, Justus-von-Liebig-Weg 3, 37077, Göttingen, Germany ; Stellar Astrophysics Centre, Department of Physics and Astronomy, Aarhus University, Ny Munkegade 120, 8000, Aarhus C, Denmark
Themeßl, N.; Max-Planck-Institut für Sonnensystemforschung, Justus-von-Liebig-Weg 3, 37077, Göttingen, Germany ; Stellar Astrophysics Centre, Department of Physics and Astronomy, Aarhus University, Ny Munkegade 120, 8000, Aarhus C, Denmark
Kallinger, T.; Institut für Astronomie, Universität Wien, Türkenschanzstr. 17, 1180, Wien, Austria
García, R. A.; Laboratoire AIM, CEA/DSM - CNRS - Univ. Paris Diderot - IRFU/SAp, Centre de Saclay, 91191, Gif-sur-Yvette Cedex, France
Mathur, S.; Space Science Institute, 4750 Walnut Street Suite 205, Boulder, CO, 80301, USA
Baudin, F.; Institut dÁstrophysique Spatiale, UMR8617, CNRS, Université Paris XI, Bâtiment 121, 91405, Orsay Cedex, France
Beers, T. C.; Dept. of Physics and JINA-CEE: Joint Institute for Nuclear Astrophysics - Center for the Evolution of the Elements, Univ. of Notre Dame, Notre Dame, IN, 46530, USA
Cunha, K.; Observatório Nacional, Rua Gal. José Cristino 77, 20921-400, Rio de Janeiro, Brazil
Harding, P.; 57 Department of Astronomy, Case Western Reserve University, Cleveland, OH, 44106, USA
Holtzman, J.; New Mexico State University, Las Cruces, NM, 88003, USA
Majewski, S.; Department of Astronomy, University of Virginia, PO Box 400325, Charlottesville, VA, 22904-4325, USA
Mészáros, Sz; ELTE Gothard Astrophysical Observatory, 9704 Szombathely, Szent Imre herceg st., 112, Hungary ; Department of Astronomy, Indiana University, Bloomington, IN, 47405, USA
Nidever, D.; Dept. of Astronomy, University of Michigan, Ann Arbor, MI, 48104, USA
Pan, K.; New Mexico State University, Las Cruces, NM, 88003, USA ; Apache Point Observatory, PO Box 59, Sunspot, NM, 88349, USA
Schiavon, R. P.; Astrophysics Research Institute, Liverpool John Moores University, IC2, Liverpool Science Park 146, Brownlow Hill Liverpool, L3 5RF, UK
Shetrone, M. D.; McDonald Observatory, University of Texas at Austin, HC75 Box 1337-MCD, Fort Davis, TX, 79734, USA
Schneider, D. P.; Department of Astronomy and Astrophysics, The Pennsylvania State University, University Park, PA, 16802, USA ; Institute for Gravitation and the Cosmos, The Pennsylvania State University, University Park, PA, 16802, USA
Stassun, K.; Vanderbilt University, Dept. of Physics & Astronomy, VU Station B 1807, Nashville, TN, 37235, USA)
