Young α-enriched giant stars in the solar neighbourhood

Marie Martig, Hans Walter Rix, Victor Silva Aguirre, Saskia Hekker, Benoit Mosser, Yvonne Elsworth, Jo Bovy, Dennis Stello, Friedrich Anders, Rafael A. García, Jamie Tayar, Thaíse S. Rodrigues, Sarbani Basu, Ricardo Carrera, Tugdual Ceillier, William J. Chaplin, Cristina Chiappini, Peter M. Frinchaboy, D. A. García-Hernández, Fred R. HeartyJon Holtzman, Jennifer A. Johnson, Steven R. Majewski, Savita Mathur, Szabolcs Mészáros, Andrea Miglio, David Nidever, Kaike Pan, Marc Pinsonneault, Ricardo P. Schiavon, Donald P. Schneider, Aldo Serenelli, Matthew Shetrone, Olga Zamora

Research output: Contribution to journalArticlepeer-review

89 Scopus citations

Abstract

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 [α/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 stellarmasses 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 [α/Fe], at least 14 out of 241 stars with [α/Fe] >0.13 are younger than 6 Gyr. Five stars with [α/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 α-rich stars (i.e. ages greater than 8-9 Gyr). Such unusual α-rich young stars have also been detected by other surveys, but defy simple explanations in a galaxy evolution context.

Original languageEnglish (US)
Pages (from-to)2230-2243
Number of pages14
JournalMonthly Notices of the Royal Astronomical Society
Volume451
Issue number2
DOIs
StatePublished - May 1 2015

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

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