Carbon-enhanced metal-poor stars in the SDSS-APOGEE database

Abstract

We identify six new CEMP stars ([C/Fe]>+0.7 and [Fe/H]< -1.8) and another seven likely candidates within the APOGEE database following Data Release 12. These stars have chemical compositions typical of metal-poor halo stars, e.g., mean [$\alpha$/Fe] = +0.24$\pm$0.24, based on the ASPCAP pipeline results. A lack of heavy element spectral lines impedes further sub-classification of these CEMP stars, however, based on radial velocity scatter, we predict most are not CEMP-s stars which are typically found in binary systems. Only one object, 2M15312547+4220551, may be in a binary since it exhibits a scatter in its radial velocity of 1.7 $\pm$0.6 km s${}^{-1}$ based on three visits over a 25.98 day baseline. Optical observations are now necessary to confirm the stellar parameters and low metallicities of these stars, to determine the heavy-element abundance ratios and improve the precision in the derived abundances, and to examine their CEMP sub-classifications.

20 pages, 9 tables, 9 figures: Accepted for publication in MNRAS

References in corpus (29)

• A grid of MARCS model atmospheres for late-type stars I. Methods and general properties
• The Radial Velocity Experiment (RAVE): first data release
• The GALAH Survey: Scientific Motivation
• Cats and Dogs, Hair and A Hero: A Quintet of New Milky Way Companions
• The RAVE Survey: Constraining the Local Galactic Escape Speed
• Carbon Enhanced Metal-Poor Stars. I. Chemical Compositions of 26 Stars
• A Search for Stars of Very Low Metal Abundance. VI. Detailed Abundances of 313 Metal-Poor Stars
• First stars VI - Abundances of C, N, O, Li, and mixing in extremely metal-poor giants. Galactic evolution of the light elements
• Carbon-Enhanced Metal-Poor Star Frequencies in the Galaxy: Corrections for the Effect of Evolutionary Status on Carbon Abundances
• A high resolution VLT/FLAMES study of individual stars in the centre of the Fornax dwarf spheroidal galaxy
• The intermediate neutron-capture process and carbon-enhanced metal-poor stars
• Observational Constraints on First-Star Nucleosynthesis. I. Evidence for Multiple Progenitors of CEMP-no Stars
• Constraining the Galaxy's dark halo with RAVE stars
• TOPoS: II. On the bimodality of carbon abundance in CEMP stars. Implications on the early chemical evolution of galaxies
• Binarity in Carbon-Enhanced Metal-Poor stars
• First stars IX -Mixing in extremely metal-poor giants. Variation of the 12C/13C, [Na/Mg] and [Al/Mg] ratios
• The Hamburg/ESO R-process Enhanced Star survey (HERES) III. HE 0338-3945 and the formation of the r+s stars
• An Elemental Assay of Very, Extremely, and Ultra Metal-Poor Stars
• New H-band Stellar Spectral Libraries for the SDSS-III/APOGEE survey
• Nitrogen abundances in giant stars of the globular cluster NGC 6752
• Tracing Sagittarius Structure with SDSS and SEGUE Imaging and Spectroscopy
• The first stars: CEMP--no stars and signatures of spinstars
• The first carbon-enhanced metal-poor star found in the Sculptor dwarf spheroidal
• Chemical gradients in the Milky Way from the RAVE data. II. Giant stars
• CH stars at High Galactic Latitudes
• Spectroscopic Signatures of Extra-Tidal Stars Around the Globular Clusters NGC 6656 (M22), NGC 3201 and NGC 1851 from RAVE
• Chemical Cartography. I. A Carbonicity Map of the Galactic Halo
• Chemical abundances in the globular clusters NGC 5024 and NGC 5466 from optical and infrared spectroscopy
• Scl-1013644: a CEMP-s star in the Sculptor Dwarf Spheroidal Galaxy

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• Pristine IX: CFHT ESPaDOnS Spectroscopic Analysis of 115 Bright Metal-Poor Candidate Stars
• On the inconsistency of [C/Fe] abundances and the fractions of carbon-enhanced metal-poor stars among various stellar surveys
• Metal-poor stars observed with the automated planet finder telescope. I. Discovery of five carbon-enhanced metal-poor stars from LAMOST
• Predicting metallicities and carbon abundances from Gaia XP spectra for (carbon-enhanced) metal-poor stars
• The metal-poor tail of the APOGEE survey I. Uncovering [Fe/H] < -2.5 stars from the inner Galaxy to the Magellanic Clouds