Spectroscopic Validation of Low-metallicity Stars from RAVE
Abstract
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 [{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 [α /{{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.
- Publication:
-
The Astronomical Journal
- Pub Date:
- June 2018
- DOI:
- 10.3847/1538-3881/aac20c
- arXiv:
- arXiv:1805.00608
- Bibcode:
- 2018AJ....155..256P
- Keywords:
-
- Galaxy: halo;
- stars: abundances;
- stars: atmospheres;
- stars: carbon;
- stars: Population II;
- techniques: imaging spectroscopy;
- Astrophysics - Solar and Stellar Astrophysics;
- Astrophysics - Astrophysics of Galaxies
- E-Print:
- 134 pages, accepted for publication in AJ