Chemical Abundances of Main-sequence, Turnoff, Subgiant, and Red Giant Stars from APOGEE Spectra. I. Signatures of Diffusion in the Open Cluster M67

Research output: Contribution to journalArticle

Abstract

Detailed chemical abundance distributions for 14 elements are derived for eight high-probability stellar members of the solar metallicity old open cluster M67 with an age of ∼4 Gyr. The eight stars consist of four pairs, with each pair occupying a distinct phase of stellar evolution: two G dwarfs, two turnoff stars, two G subgiants, and two red clump (RC) K giants. The abundance analysis uses near-IR high-resolution spectra (λ1.5-1.7 μm) from the Apache Point Observatory Galactic Evolution Experiment survey and derives abundances for C, N, O, Na, Mg, Al, Si, K, Ca, Ti, V, Cr, Mn, and Fe. Our derived stellar parameters and metallicity for 2M08510076+1153115 suggest that this star is a solar twin, exhibiting abundance differences relative to the Sun of ≤0.04 dex for all elements. Chemical homogeneity is found within each class of stars (∼0.02 dex), while significant abundance variations (∼0.05-0.20 dex) are found across the different evolutionary phases; the turnoff stars typically have the lowest abundances, while the RCs tend to have the largest. Non-LTE corrections to the LTE-derived abundances are unlikely to explain the differences. A detailed comparison of the derived Fe, Mg, Si, and Ca abundances with recently published surface abundances from stellar models that include chemical diffusion provides a good match between the observed and predicted abundances as a function of stellar mass. Such agreement would indicate the detection of chemical diffusion processes in the stellar members of M67.

Details

Authors
  • Diogo Souto
  • Katia Cunha
  • Verne V. Smith
  • C. Allende Prieto
  • D. A. García-Hernández
  • Marc Pinsonneault
  • Parker Holzer
  • Peter Frinchaboy
  • Jon Holtzman
  • J. A. Johnson
  • Henrik Jönsson
  • Steven R. Majewski
  • Matthew Shetrone
  • Jennifer Sobeck
  • Guy Stringfellow
  • Johanna Teske
  • Olga Zamora
  • Gail Zasowski
  • Ricardo Carrera
  • Keivan Stassun
  • And 4 others
  • J. G. Fernandez-Trincado
  • Sandro Villanova
  • Dante Minniti
  • Felipe Santana
Organisations
External organisations
  • National Observatory Brazil
  • University of Arizona
  • Instituto de Astrofísica de Canarias
  • University of La Laguna (ULL)
  • Ohio State University
  • University of Utah
  • Texas Christian University
  • New Mexico State University
  • University of Virginia
  • University of Texas at Austin
  • University of Colorado
  • Carnegie Institution for Science
  • INAF - Osservatorio Astronomico di Padova
  • Vanderbilt University
  • University of Concepción
  • University of Burgundy - Franche-Comté
  • Pontifical Catholic University of Chile
  • University of Chile
  • National Optical Astronomy Observatory
Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Astronomy, Astrophysics and Cosmology

Keywords

  • diffusion, infrared: stars, open clusters and associations: general, stars: abundances
Original languageEnglish
Article number14
JournalAstrophysical Journal
Volume857
Issue number1
Publication statusPublished - 2018 Apr 10
Publication categoryResearch
Peer-reviewedYes