论文标题
发现具有极高的碳和氧气的热分子的发现
Discovery of hot subdwarfs with extremely high carbon and oxygen abundances
论文作者
论文摘要
富含氦的细分恒星（SDOS）是白矮人进化状态下的热恒星。它们中的大多数在TEFF范围内具有有效的温度和表面重力= 40,000-50,000 K，Log G = 5.5-6.0。他们的气氛以氦气为主。如果完全存在，则C，N和O是微量元素。丰度模式是用单星进化过程中的核合成（晚期氦芯闪光灯）或二元He-core白矮人合并来解释的。在这里，我们宣布发现了两种缺乏氢的SDO（PG1654+322和PG1528+025），它们表现出异常强的碳和氧线。通过大型双眼望远镜和Lamost调查获得的光谱的非LTE模型大气分析显示，C（〜20％）和O（〜20％）的大丰度（〜20％），两颗恒星位于氦气主序列附近。两者都建立了新的光谱类缺陷型细分（Co-SDO），并且可以被识别为He-Core白矮人的残余物，该残余物促进了合并低质量的白色矮人的合并的物质。我们得出的结论是，除了经历了晚期氦壳闪光灯的单星的进化外，共同代表了一个替代性进化渠道。
Helium rich subdwarf O stars (sdOs) are hot compact stars in a pre-white dwarf evolutionary state. Most of them have effective temperatures and surface gravities in the range Teff = 40,000-50,000 K and log g = 5.5-6.0. Their atmospheres are helium dominated. If present at all, C, N, and O are trace elements. The abundance patterns are explained in terms of nucleosynthesis during single star evolution (late helium core flash) or a binary He-core white dwarf merger. Here we announce the discovery of two hot hydrogen-deficient sdOs (PG1654+322 and PG1528+025) that exhibit unusually strong carbon and oxygen lines. A non-LTE model atmosphere analysis of spectra obtained with the Large Binocular Telescope and by the LAMOST survey reveals astonishingly high abundances of C (~20%) and O (~20%) and that the two stars are located close to the helium main sequence. Both establish a new spectroscopic class of hot H-deficient subdwarfs (CO-sdO) and can be identified as the remnants of a He-core white dwarf that accreted matter of a merging low-mass CO-core white dwarf. We conclude that the CO-sdOs represent an alternative evolutionary channel creating PG1159 stars besides the evolution of single stars that experience a late helium-shell flash.
