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  • Shetrone, MatthewUniv Texas Austin, McDonald Observ, 32 Fowlkes Rd, Austin, TX 79734 USA.,University of Texas at Austin (author)

Constraining Metallicity-dependent Mixing and Extra Mixing Using [C/N] in Alpha-rich Field Giants

  • Article/chapterEnglish2019

Publisher, publication year, extent ...

  • 2019-02-19
  • Institute of Physics Publishing (IOPP),2019
  • printrdacarrier

Numbers

  • LIBRIS-ID:oai:DiVA.org:mau-65197
  • https://urn.kb.se/resolve?urn=urn:nbn:se:mau:diva-65197URI
  • https://doi.org/10.3847/1538-4357/aaff66DOI
  • https://lup.lub.lu.se/record/63748f3d-7bb1-4ae2-8dd7-8ee9cd7ba706URI

Supplementary language notes

  • Language:English
  • Summary in:English

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Classification

  • Subject category:ref swepub-contenttype
  • Subject category:art swepub-publicationtype

Notes

  • Internal mixing on the giant branch is an important process which affects the evolution of stars and the chemical evolution of the galaxy. While several mechanisms have been proposed to explain this mixing, better empirical constraints are necessary. Here, we use [C/N] abundances in 26,097 evolved stars from the SDSS-IV/APOGEE-2 Data Release 14 to trace mixing and extra mixing in old field giants with -1.7 < [Fe/H] < 0.1. We show that the APOGEE [C/N] ratios before any dredge-up occurs are metallicity dependent, but that the change in [C/N] at the first dredge-up is metallicity independent for stars above [Fe/H] similar to -1. We identify the position of the red giant branch (RGB) bump as a function of metallicity, note that a metallicity-dependent extra mixing episode takes place for low-metallicity stars ([Fe/H] < -0.4) 0.14 dex in log g above the bump, and confirm that this extra mixing is stronger at low metallicity, reaching Delta[C/N] = 0.58 dex at [Fe/H] = -1.4. We show evidence for further extra mixing on the upper giant branch, well above the bump, among the stars with [Fe/H] < -1.0. This upper giant branch mixing is stronger in the more metal-poor stars, reaching 0.38 dex in [C/N] for each 1.0 dex in log g. The APOGEE [C/N] ratios for red clump (RC) stars are significantly higher than for stars at the tip of the RGB, suggesting additional mixing processes occur during the helium flash or that unknown abundance zero points for C and N may exist among the RC sample. Finally, because of extra mixing, we note that current empirical calibrations between [C/N] ratios and ages cannot be naively extrapolated for use in low-metallicity stars specifically for those above the bump in the luminosity function.

Subject headings and genre

Added entries (persons, corporate bodies, meetings, titles ...)

  • Tayar, JamieOhio State Univ, Dept Astron, 140 W 18th Ave, Columbus, OH 43210 USA.;Univ Hawaii, Inst Astron, 2680 Woodlawn Dr, Honolulu, HI 96822 USA.,University of Hawaii at Manoa,Ohio State University (author)
  • Johnson, Jennifer A.Ohio State Univ, Dept Astron, 140 W 18th Ave, Columbus, OH 43210 USA.;Ohio State Univ, Ctr Cosmol & AstroParticle Phys, 191 West Woodruff Ave, Columbus, OH 43210 USA.,Ohio State University (author)
  • Somers, GarrettVanderbilt Univ, Dept Phys & Astron, 6301 Stevenson Circle, Nashville, TN 37235 USA.,Vanderbilt University (author)
  • Pinsonneault, Marc H.Ohio State Univ, Dept Astron, 140 W 18th Ave, Columbus, OH 43210 USA.;Ohio State Univ, Ctr Cosmol & AstroParticle Phys, 191 West Woodruff Ave, Columbus, OH 43210 USA.,Ohio State University (author)
  • Holtzman, Jon A.New Mexico State Univ, Dept Astron, Las Cruces, NM 88003 USA.,New Mexico State University(Swepub:lu)jo6205ho (author)
  • Hasselquist, StenNew Mexico State Univ, Dept Astron, Las Cruces, NM 88003 USA.,New Mexico State University (author)
  • Masseron, ThomasIAC, E-38205 Tenerife, Spain.;ULL, Dept Astrofis, E-38206 Tenerife, Spain.,University of La Laguna (ULL),Instituto de Astrofísica de Canarias (author)
  • Meszaros, SzabolcsEotvos Lorand Univ, Gothard Astrophys Observ, Szombathely, Hungary.;Hungarian Acad Sci, Budapest, Hungary.,Eötvös Loránd University (author)
  • Jönsson, HenrikLund University,Lunds universitet,Astronomi - Genomgår omorganisation,Institutionen för astronomi och teoretisk fysik - Genomgår omorganisation,Naturvetenskapliga fakulteten,Lund Observatory - Undergoing reorganization,Department of Astronomy and Theoretical Physics - Undergoing reorganization,Faculty of Science(Swepub:lu)astr-hkj (author)
  • Hawkins, KeithUniv Texas Austin, Dept Astron, 2515 Speedway Blvd, Austin, TX 78712 USA.,University of Texas at Austin (author)
  • Sobeck, JenniferUniv Washington, Dept Astron, Box 351580, Seattle, WA 98195 USA.,University of Washington (author)
  • Zamora, OlgaIAC, E-38205 Tenerife, Spain.;ULL, Dept Astrofis, E-38206 Tenerife, Spain.,University of La Laguna (ULL),Instituto de Astrofísica de Canarias (author)
  • Garcia-Hernandez, D. A.IAC, E-38205 Tenerife, Spain.,University of La Laguna (ULL),Instituto de Astrofísica de Canarias (author)
  • Univ Texas Austin, McDonald Observ, 32 Fowlkes Rd, Austin, TX 79734 USA.University of Texas at Austin (creator_code:org_t)

Related titles

  • In:Astrophysical Journal: Institute of Physics Publishing (IOPP)872:20004-637X1538-4357

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