Spectroscopic Validation of Low-metallicity Stars from RAVE

• Main Authors: Placco, Vinicius M. (Author), Beers, Timothy C. (Author), Santucci, Rafael M. (Author), Chanamé, Julio (Author), Sepúlveda, María Paz (Author), Coronado, Johanna (Author), Points, Sean D. (Author), Kaleida, Catherine C. (Author), Rossi, Silvia (Author), Kordopatis, Georges (Author), Lee, Young Sun (Author), Matijevič, Gal (Author), Frebel, Anna L. (Author), Hansen, Terese T. (Author), Holmbeck, Erika M. (Author), Rasmussen, Kaitlin C. (Author), Roederer, Ian U. (Author), Sakari, Charli M. (Author), Whitten, Devin D. (Author)
• Other Authors: Massachusetts Institute of Technology. Department of Physics (Contributor), MIT Kavli Institute for Astrophysics and Space Research (Contributor)
• Format: Article
• Language: English
• Published: American Astronomical Society, 2019-06-05T14:56:33Z.
• Subjects: Article
• Online Access: Get fulltext

We present results from a medium-resolution (R ∼ 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 α-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 ≤ -1.0, 61% have ≤ -2.0, and 3% have ≤ -3.0 (with four stars at ≤ -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 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.