Adding the s-Process Element Cerium to the APOGEE Survey: Identification and Characterization of Ce II Lines in the H-band Spectral Window

Research output: Contribution to journalArticle

Abstract

Nine Ce ii lines have been identified and characterized within the spectral window observed by the Apache Point Observatory Galactic Evolution Experiment (APOGEE) survey (between λ1.51 and 1.69 μm). At solar metallicities, cerium is an element that is produced predominantly as a result of the slow capture of neutrons (the s-process) during asymptotic giant branch stellar evolution. The Ce ii lines were identified using a combination of a high-resolution (R= λ/δλ) Fourier Transform Spectrometer (FTS) spectrum of α Boo and an APOGEE spectrum (R = 22,400) of a metal-poor, but s-process enriched, red giant (2M16011638-1201525). Laboratory oscillator strengths are not available for these lines. Astrophysical gf-values were derived using α Boo as a standard star, with the absolute cerium abundance in α Boo set by using optical Ce ii lines that have precise published laboratory gf-values. The near-infrared Ce ii lines identified here are also analyzed, as consistency checks, in a small number of bright red giants using archival FTS spectra, as well as a small sample of APOGEE red giants, including two members of the open cluster NGC 6819, two field stars, and seven metal-poor N- and Al-rich stars. The conclusion is that this set of Ce ii lines can be detected and analyzed in a large fraction of the APOGEE red giant sample and will be useful for probing chemical evolution of the s-process products in various populations of the Milky Way.

Details

Authors
  • Katia Cunha
  • Verne V. Smith
  • Sten Hasselquist
  • Diogo Souto
  • Matthew D. Shetrone
  • Carlos Allende Prieto
  • Dmitry Bizyaev
  • Peter Frinchaboy
  • D. Anibal García-Hernández
  • Jon Holtzman
  • Jennifer A. Johnson
  • Henrik Jönsson
  • Steven R. Majewski
  • Szabolcs Mészáros
  • David Nidever
  • Mark Pinsonneault
  • Ricardo P. Schiavon
  • Jennifer Sobeck
  • Michael F. Skrutskie
  • Olga Zamora
  • And 2 others
  • Gail Zasowski
  • J. G. Fernández-Trincado
External organisations
  • University of Arizona
  • National Observatory Brazil
  • National Optical Astronomy Observatory
  • New Mexico State University
  • University of Texas at Austin
  • Instituto de Astrofísica de Canarias
  • University of La Laguna (ULL)
  • Apache Point Observatory
  • Lomonosov Moscow State University
  • Texas Christian University
  • Ohio State University
  • University of Virginia
  • ELTE Gothard Astrophysical Observatory
  • Liverpool John Moores University
  • Vanderbilt University
  • Space Telescope Science Institute
  • University of Utah
  • University of Concepción
Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Astronomy, Astrophysics and Cosmology

Keywords

  • stars: abundances
Original languageEnglish
Article number145
JournalAstrophysical Journal
Volume844
Issue number2
Publication statusPublished - 2017 Aug 1
Publication categoryResearch
Peer-reviewedYes
Externally publishedYes