Binarity in carbon-enhanced metal-poor stars

By E. Starkenburg, M. Shetrone, A. McConnachie, K. Venn. 2014

135 citations recorded by the source corpus.

A substantial fraction of the lowest metallicity stars show very high enhancements in carbon. It is debated whether these enhancements reflect the stars' birth composition, or if their atmospheres were subsequently polluted, most likely by accretion from an AGB binary companion. Here we investigate and compare the binary properties of three carbon-enhanced sub-classes: The metal-poor CEMP-s stars that are additionally enhanced in barium; the higher metallicity (sg)CH- and Ba II stars also enhanced in barium; and the metal-poor CEMP-no stars, not enhanced in barium. Through comparison with simulations, we demonstrate that all barium-enhanced populations are best represented by a ~100% binary fraction with a shorter period distribution of at maximum ~20,000 days. This result greatly strengthens the hypothesis that a similar binary mass transfer origin is responsible for their chemical patterns. For the CEMP-no group we present new radial velocity data from the Hobby-Eberly Telescope for 15 stars to supplement the scarce literature data. Two of these stars show indisputable signatures of binarity. The complete CEMP-no dataset is clearly inconsistent with the binary properties of the CEMP-s class, thereby strongly indicating a different physical origin of their carbon enhancements. The CEMP-no binary fraction is still poorly constrained, but the population resembles more the binary properties in the Solar Neighbourhood.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/33ec711a819bef255a64785a40eb2e278c27e706

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Astronomy and Astrophysics

1. Hans-Walter Rix
2. Jo Bovy
3. Timothy C. Beers
4. I. Minchev
5. S. Majewski
6. M. Walker
7. C. Chiappini
8. A. Helmi

In Instrumentation

1. M. Walker
2. A. Frebel
3. J. Norris
4. E. Olszewski
5. Timothy C. Beers
6. M. Mateo
7. A. Helmi
8. S. Majewski

Citations in the corpus

• Chemical tagging with APOGEE: Discovery of a large population of N-rich stars in the inner Galaxy (2016, background): “Classical CH-stars, like Ba and CEMPs stars owe their peculiar composition to mass transfer from a relatively low-mass (M∼1.5-4M⊙) companion (see, e.g., McClure & Woodsworth 1990; Lucatello et al. 2005a; Starkenburg et al. 2014).”
• Near-Field Cosmology with Extremely Metal-Poor Stars (2015, background): “Currently, radial velocity monitoring of C-rich (CEMP-no) stars with [Fe/H] ∼ < − 3.0 does not support universal binarity among this group of stars (Hansen, Andersen & Nordström 2013, Norris et al. 2013, Starkenburg et al. 2014).”
• DETAILED CHEMICAL ABUNDANCES IN THE r-PROCESS-RICH ULTRA-FAINT DWARF GALAXY RETICULUM 2 (2016, background): “CEMP stars with no enhancement of slow n-capture process (s-process) material, like those in Ret 2, likely reflect their natal composition (e.g., Ryan et al. 2005; Norris et al. 2013; Starkenburg et al. 2014; Hansen et al. 2015a,c).”
• Dawes Review 6: The Impact of Companions on Stellar Evolution (2016, background): “Recent observations have shown that the CEMP stars are truly equivalent to CH and barium stars (Starkenburg et al., 2014), and that the amount of accreted material is a function of orbital period (Merle et al., 2016).”