4.6 Article

Spectroscopic Validation of Low-metallicity Stars from RAVE

Journal

ASTRONOMICAL JOURNAL
Volume 155, Issue 6, Pages -

Publisher

IOP Publishing Ltd
DOI: 10.3847/1538-3881/aac20c

Keywords

Galaxy: halo; stars: abundances; stars: atmospheres; stars: carbon; stars: Population II; techniques: imaging spectroscopy

Funding

  1. Physics Frontier Center/JINA Center for the Evolution of the Elements (JINA-CEE) - US National Science Foundation [PHY 14-30152]
  2. FAPESP
  3. CAPES/PROEX
  4. CNPq
  5. National Research Foundation (NFR) of Korea grant - Ministry of Science and ICT [2017R1A5A1070354, NRF2015R1C1A1A02036658, NRF-2018R1A2B6003961]
  6. ESO [095.D-0202(A), 096.D-0018(A), 097.D0196(A), 098.D-0434(A), 099.D-0428(A)]

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We present results from a medium-resolution (R similar to 2000) spectroscopic follow-up campaign of 1694 bright (V < 13.5), very metal-poor star candidates from the RAdial Velocity Experiment (RAVE). Initial selection of the low-metallicity targets was based on the stellar parameters published in RAVE Data Releases 4 and 5. Follow up was accomplished with the Gemini-N and Gemini-S, the ESO/NTT, the KPNO/Mayall, and the SOAR telescopes. The wavelength coverage for most of the observed spectra allows for the determination of carbon and a-element abundances, which are crucial for considering the nature and frequency of the carbon-enhanced metal-poor (CEMP) stars in this sample. We find that 88% of the observed stars have[Fe H] <= -1.0, 61% have [Fe H] <= -2.0, and 3% have[Fe H] <= -3.0 (with four stars at[Fe H] <= -3.5). There are 306 CEMP star candidates in this sample, and we identify 169 CEMP Group. I, 131 CEMP Group. II, and 6 CEMP Group. III stars from the A(C) versus [Fe/H] diagram. Inspection of the[alpha/C] abundance ratios reveals that five of the CEMP Group. II stars can be classified as mono-enriched second-generation stars. Gaia DR1 matches were found for 734 stars, and we show that transverse velocities can be used as a confirmatory selection criteria for low-metallicity candidates. Selected stars from our validated list are being followed-up with high-resolution spectroscopy to reveal their full chemical-abundance patterns for further studies.

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