SODIUM AND OXYGEN ABUNDANCES IN THE OPEN CLUSTER NGC 6791 FROM APOGEE H-BAND SPECTROSCOPY

Journal Article · Sat Jan 10 00:00:00 EST 2015 · Astrophysical Journal Letters

DOI:https://doi.org/10.1088/2041-8205/798/2/L41· OSTI ID:22364636

Cunha, Katia; Souto, Diogo ^[1]; Smith, Verne V. ^[2]; Johnson, Jennifer A. ^[3]; Bergemann, Maria ^[4]; Mészáros, Szabolcs ^[5]; Shetrone, Matthew D. ^[6]; Prieto, Carlos Allende ^[7]; Schiavon, Ricardo P. ^[8]; Frinchaboy, Peter ^[9]; Zasowski, Gail ^[10]; Bizyaev, Dmitry ^[11]; Holtzman, Jon ^[12]; García Pérez, Ana E.; Majewski, Steven R. ^[13]; Nidever, David ^[14]; Beers, Timothy ^[15]; Carrera, Ricardo ^[16]; Geisler, Doug ^[17]; Gunn, James ^[18] ; others, and

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1. Observatório Nacional, São Cristóvão, Rio de Janeiro (Brazil)
2. National Optical Astronomy Observatories, Tucson, AZ 85719 (United States)
3. Department of Astronomy, The Ohio State University, Columbus, OH 43210 (United States)
4. Max-Planck-Institut für Astronomy, D-69117, Heidelberg (Germany)
5. ELTE Gothard Astrophysical Observatory, H-9704 Szombathely (Hungary)
6. Department of Astronomy and McDonald Observatory, University of Texas, Austin, TX 78712 (United States)
7. Instituto de Astrofísica de Canarias, E-38205 La Laguna, Tenerife (Spain)
8. Astrophysics Research Institute, Liverpool John Moores University, Liverpool L3 5RF (United Kingdom)
9. Texas Christian University, Fort Worth, TX (United States)
10. Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218 (United States)
11. Apache Point Observatory, Sunspot, NM 88349 (United States)
12. Department of Astronomy, New Mexico State University, Las Cruces, NM 88003 (United States)
13. Department of Astronomy, University of Virginia, Charlottesville, VA 22904 (United States)
14. Department of Astronomy, University of Michigan, Ann Arbor, MI 48109 (United States)
15. Department of Physics and JINA Center for the Evolution of the Elements, University of Notre Dame, Notre Dame, IN 46556 (United States)
16. Instituto de Astrofísica de Canarias, La Laguna, E-38200 Tenerife (Spain)
17. Departamento de Astronomia, Casilla 160-C, Universidad de Concepcion (Chile)
18. Department of Astrophysics, Princeton University, Princeton, NJ 08540 (United States)

The open cluster NGC 6791 is among the oldest, most massive, and metal-rich open clusters in the Galaxy. High-resolution H-band spectra from the Apache Point Observatory Galactic Evolution Experiment (APOGEE) of 11 red giants in NGC 6791 are analyzed for their chemical abundances of iron, oxygen, and sodium. The abundances of these three elements are found to be homogeneous (with abundance dispersions at the level of ∼0.05-0.07 dex) in these cluster red giants, which span much of the red-giant branch (T {sub eff} ∼ 3500-4600 K), and include two red clump giants. From the infrared spectra, this cluster is confirmed to be among the most metal-rich clusters in the Galaxy (([Fe/H]) = 0.34 ± 0.06) and is found to have a roughly solar value of [O/Fe] and slightly enhanced [Na/Fe]. Our non-LTE calculations for the studied Na I lines in the APOGEE spectral region (16373.86 Å and 16388.85 Å) indicate only small departures from LTE (≤0.04 dex) for the parameter range and metallicity of the studied stars. The previously reported double population of cluster members with different Na abundances is not found among the studied sample.

• OSTI ID: 22364636
• Journal Information: Astrophysical Journal Letters, Vol. 798, Issue 2; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 2041-8205
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
ELEMENT ABUNDANCE
GALACTIC EVOLUTION
GALAXIES
INFRARED SPECTRA
IRON
METALLICITY
OXYGEN
RESOLUTION
SODIUM
STAR CLUSTERS
STARS