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          Institute: MPI für Astronomie     Collection: Publikationen_mpia     Display Documents



ID: 720108.0, MPI für Astronomie / Publikationen_mpia
Young α-enriched giant stars in the solar neighbourhood
Authors:Martig, M.; Rix, H.-W.; Aguirre, V. S.; Hekker, S.; Mosser, B.; Elsworth, Y.; Bovy, J.; Stello, D.; Anders, F.; García, R. A.; Tayar, J.; Rodrigues, T. S.; Basu, S.; Carrera, R.; Ceillier, T.; Chaplin, W. J.; Chiappini, C.; Frinchaboy, P. M.; García-Hernández, D. A.; Hearty, F. R.; Holtzman, J.; Johnson, J. A.; Majewski, S. R.; Mathur, S.; Mészáros, S.; Miglio, A.; Nidever, D.; Pan, K.; Pinsonneault, M.; Schiavon, R. P.; Schneider, D. P.; Serenelli, A.; Shetrone, M.; Zamora, O.
Date of Publication (YYYY-MM-DD):2015
Title of Journal:Monthly Notices of the Royal Astronomical Society
Volume:451
Issue / Number:2
Start Page:2230
End Page:2243
Audience:Not Specified
Abstract / Description:We derive age constraints for 1639 red giants in the APOKASC sample for which seismic parameters from Kepler, as well as effective temperatures, metallicities and [alpha/Fe] values from APOGEE DR12 (Apache Point Observatory Galactic Evolution Experiment Data Release 12) are available. We investigate the relation between age and chemical abundances for these stars, using a simple and robust approach to obtain ages. We first derive stellar masses using standard seismic scaling relations, then determine the maximum possible age for each star as function of its mass and metallicity, independently of its evolutionary stage. While the overall trend between maximum age and chemical abundances is a declining fraction of young stars with increasing [alpha/Fe], at least 14 out of 241 stars with [alpha/Fe] >0.13 are younger than 6 Gyr. Five stars with [alpha/Fe] >=0.2 have ages below 4 Gyr. We examine the effect of modifications in the standard seismic scaling relations, as well as the effect of very low helium fractions, but these changes are not enough to make these stars as old as usually expected for alpha-rich stars (i.e. ages greater than 8-9 Gyr). Such unusual alpha-rich young stars have also been detected by other surveys, but defy simple explanations in a galaxy evolution context.
Free Keywords:stars: abundances; stars: fundamental parameters
External Publication Status:published
Document Type:Article
Communicated by:N. N.
Affiliations:MPI für Astronomie
Identifiers:ISSN:0035-8711
URL:http://cdsads.u-strasbg.fr/abs/2015MNRAS.451.2230M
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