Chemical Abundances of Main-sequence, Turnoff, Subgiant, and Red Giant Stars from APOGEE Spectra. II. Atomic Diffusion in M67 Stars

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Chemical abundances for 15 elements (C, N, O, Na, Mg, Al, Si, K, Ca, Ti, V, Cr, Mn, Fe, and Ni) are presented for 83 stellar members of the 4 Gyr old solar-metallicity open cluster M67. The sample contains stars spanning a wide range of evolutionary phases, from G dwarfs to red clump stars. The abundances were derived from near-IR (λ1.5-1.7 μm) high-resolution spectra (R ,F= ,F22,500) from the SDSS-IV/Apache Point Observatory Galactic Evolution Experiment (APOGEE) survey. A 1D local thermodynamic equilibrium abundance analysis was carried out using the APOGEE synthetic spectral libraries, via χ 2 minimization of the synthetic and observed spectra with the qASPCAP code. We found significant abundance differences (∼0.05-0.30 dex) between the M67 member stars as a function of the stellar mass (or position on the Hertzsprung-Russell diagram), where the abundance patterns exhibit a general depletion (in [X/H]) in stars at the main-sequence turnoff. The amount of the depletion is different for different elements. We find that atomic diffusion models provide, in general, good agreement with the abundance trends for most chemical species, supporting recent studies indicating that measurable atomic diffusion operates in M67 stars.


  • Diogo Souto
  • C. Allende Prieto
  • Katia Cunha
  • Marc Pinsonneault
  • Verne V. Smith
  • R. Garcia-Dias
  • Jo Bovy
  • D. A. Garcia-Hernández
  • Jon Holtzman
  • J. A. Johnson
  • Henrik Jönsson
  • Steve R. Majewski
  • Matthew Shetrone
  • Jennifer Sobeck
  • Olga Zamora
  • Kaike Pan
  • Christian Nitschelm
External organisations
  • Instituto de Astrofísica de Canarias
  • University of La Laguna (ULL)
  • University of Arizona
  • Ohio State University
  • University of Toronto
  • New Mexico State University
  • University of Virginia
  • University of Texas at Austin
  • Apache Point Observatory
  • University of Antofagasta
  • National Observatory Brazil
  • National Optical Astronomy Observatory
Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Astronomy, Astrophysics and Cosmology


  • diffusion, infrared: stars, open clusters and associations: general, stars: abundances
Original languageEnglish
Article number97
JournalAstrophysical Journal
Issue number1
Publication statusPublished - 2019 Mar 20
Publication categoryResearch