论文标题
脱衣舞起源于恒星：假定黑洞HR 6819和LB-1的线索
A stripped-companion origin for Be stars: clues from the putative black holes HR 6819 and LB-1
论文作者
论文摘要
HR 6819是一个明亮的（$ v = 5.36 $），蓝星最近提议是一个包含分离黑洞（BH）的三重。我们证明该系统是二进制的，不包含BH。使用光谱分解，我们将观察到的复合光谱分解为两个组成部分：快速旋转的恒星和一个缓慢旋转的B恒星，其表面重力$（\ log g \ g \ of 2.75）$。这两颗恒星均显示周期性径向速度（RV）的可变性，但是B恒星轨道的RV半增强型为$ k _ {\ rm b} =（62.7 \ pm 1）\，\ rm km \，s^，s^{ - 1} $ km \，s^{ - 1} $。这意味着B恒星的质量较小至少为10倍。B星熊燃烧的烙印的表面丰度。我们认为，B星是一个肿的，最近被剥离的氦气星，质量$ \约0.5 \，m _ {\ odot} $，目前正在签约成为热门subdwarf。 BE恒星的轨道运动避免了BH解释B恒星运动的需求。剥离的Star模型再现了系统的光度，而B恒星温度和重力的正常恒星将超过10倍以上。 HR 6819和二进制LB-1可能是通过相似通道形成的。我们使用MESA模型来研究其进化史，发现它们可能是由中间质量（$ 3-7 \，M _ {\ odot} $）的初选形成的。其当前进化阶段的寿命平均为$ 2 \ tims 10^5 $年，是BE阶段总寿命的一半。这意味着许多恒星都有热的分子和白色矮人的伴侣，并且通过从二元同伴中获得材料来形成大量的田野（$ 20-100 \％$）。
HR 6819 is a bright ($V=5.36$), blue star recently proposed to be a triple containing a detached black hole (BH). We show that the system is a binary and does not contain a BH. Using spectral decomposition, we disentangle the observed composite spectra into two components: a rapidly rotating Be star and a slowly rotating B star with low surface gravity $(\log g \approx 2.75)$. Both stars show periodic radial velocity (RV) variability, but the RV semi-amplitude of the B star's orbit is $K_{\rm B}= (62.7 \pm 1)\,\rm km\,s^{-1}$, while that of the Be star is only $K_{\rm Be} = (4.5\pm 2)\,\rm km\,s^{-1}$. This implies that the B star is less massive by at least a factor of 10. The surface abundances of the B star bear imprints of CNO burning. We argue that the B star is a bloated, recently stripped helium star with mass $\approx 0.5\,M_{\odot}$ that is currently contracting to become a hot subdwarf. The orbital motion of the Be star obviates the need for a BH to explain the B star's motion. A stripped-star model reproduces the observed luminosity of the system, while a normal star with the B star's temperature and gravity would be more than 10 times too luminous. HR 6819 and the binary LB-1 probably formed through similar channels. We use MESA models to investigate their evolutionary history, finding that they likely formed from intermediate-mass ($3-7\,M_{\odot}$) primaries stripped by slightly lower-mass secondaries and are progenitors to Be + sdOB binaries such as $ϕ$ Persei. The lifetime of their current evolutionary phase is on average $2\times 10^5$ years, of order half a percent of the total lifetime of the Be phase. This implies that many Be stars have hot subdwarf and white dwarf companions, and that a substantial fraction ($20-100\%$) of field Be stars form through accretion of material from a binary companion.
