论文标题
径向速度变异性和热分子星星的演变
Radial velocity variability and evolution of hot subdwarf stars
论文作者
论文摘要
在低质量恒星的演变中，热的细分恒星代表了一个晚期且奇特的阶段，因为它们可能是由近距离二进制相互作用形成的。在这里，我们进行了径向速度（RV）的可变性研究，对646个热门细分的样本具有带有Sloan数字天空调查（SDSS）和大型天空区域多对象光纤光谱望远镜（Lamost）光谱（Lamost）光谱[...]的多上径径速速度的样本[...]，作为诊断的最高变化，我们使用了RV-V-V-Var的级别。 $ΔRV_ {\ rm max} $。在研究的参数范围内，这两个指标都非常不均匀。一个惊人的特征是他贫穷和富裕的热门人物的完全不同的行为。虽然前者的近距离二进制很大，但几乎无法检测到后者的RV变化。这使我们得出这样的结论，即这些亚型之间可能没有进化的联系。另一方面，中级富裕和极端的HEICH SDOB/OS可能是相关的。我们进一步得出结论，绝大多数人群是通过一个或几个二进制合并渠道形成的。温度比$ \ sim24 \，000 \，{\ rm k} $降低温度的热分子往往会显示较小和较小的RV变量。这些物体可能构成具有更长时期和晚期或紧凑型伴侣的二进制组的新亚种群。极端水平分支（EHB）和相应的He-poor Hot Hot SubdWarfs匹配的RV变差性能和相应的EHB群体匹配，并确认它们之间的预测进化连接。在较高表面重力下的规范EHB下方发现的恒星显示出较大的RV变化和高RV变量的分数，这与大多数是低质量EHB星或低质量氦白色矮人的祖细胞一致的，这是一致的。
Hot subdwarf stars represent a late and peculiar stage in the evolution of low-mass stars, because they are likely formed by close binary interactions. Here we performed a radial velocity (RV) variability study of a sample of 646 hot subdwarfs with multi-epoch radial velocities from Sloan Digital Sky Survey (SDSS) and Large Sky Area Multi-Object Fibre Spectroscopic Telescope (LAMOST) spectra [...] As diagnostics we used the fraction of RV-variable stars and the distribution of the maximum RV variations $ΔRV_{\rm max}$. Both indicators turned out to be quite inhomogeneous across the studied parameter ranges. A striking feature is the completely different behaviour of He-poor and He-rich hot subdwarfs. While the former have a high fraction of close binaries, almost no significant RV variations could be detected for the latter. This led us to the conclusion that there likely is no evolutionary connection between these subtypes. Intermediate He-rich- and extreme He-rich sdOB/Os on the other hand are likely related. We conclude further that the vast majority of this population is formed via one or several binary merger channels. Hot subdwarfs with temperatures cooler than $\sim24\,000\,{\rm K}$ tend to show less and smaller RV-variations. These objects might constitute a new subpopulation of binaries with longer periods and late-type or compact companions. The RV-variability properties of the extreme horizontal branch (EHB) and corresponding post-EHB populations of the He-poor hot subdwarfs match and confirm the predicted evolutionary connection between them. Stars found below the canonical EHB at somewhat higher surface gravities show large RV-variations and a high RV-variability fraction, which is consistent with most of them being low-mass EHB stars or progenitors of low-mass helium white dwarfs in close binaries.
