The large fraction of carbon-enhanced metal-poor (CEMP) stars at lower metallicities makes them an interesting class of objects to be probed further in greater detail. They show different abundance patterns of neutron-capture elements and based on that CEMP stars are further divided into four categories. Abundances of C, N and O, along with other elements, are required to understand the different nucleosynthetic origins of the subclasses and their progenitors. We studied nine bright carbon-enhanced stars from the Milky Way halo in a metallicity range from −0.8 to −2.5. They show enhancement in C, N, O and Ba and exhibit radial velocity variation. This indicates the presence of a binary companion which might have contributed to the enhanced carbon and s-process abundance through mass transfer during its asymptotic-giant-branch (AGB) phase of evolution. Their abundance pattern of C, N and O favors low-mass nature for their binary companion.

中文翻译：

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光晕中碳增强恒星族群的氧丰度

大部分金属含量较低的碳增强贫金属 (CEMP) 恒星使它们成为一类有趣的物体，需要进一步更详细地探测。它们显示了不同的中子俘获元素丰度模式，并基于此将 CEMP 恒星进一步分为四类。需要大量的 C、N 和 O 以及其他元素来了解亚类及其祖先的不同核合成起源。我们研究了来自银河系晕的九颗明亮的碳增强恒星，金属丰度范围从 -0.8 到 -2.5。它们表现出 C、N、O 和 Ba 的增强，并表现出径向速度变化。这表明二元伴星的存在可能在其渐近巨枝 (AGB) 演化阶段通过传质促进了碳和 s 过程丰度的增加。它们的 C、N 和 O 丰度模式有利于它们的双星伴星的低质量性质。