利用径向速度揭示中等质量剥离恒星的光学隐藏伴星
Revealing Optically Hidden Companions to Intermediate-Mass Stripped Stars with Radial Velocities
- University of Toronto（多伦多大学）
- Dunlap Institute for Astronomy & Astrophysics, University of Toronto（多伦多大学邓普天文学与天体物理研究所）
- Institute of Science and Technology Austria (ISTA)（奥地利科学与技术研究院）
机构由 AI 辅助整理，请以论文原文为准。
中文总结 AI 辅助
本研究通过测量麦哲伦云中8颗中等质量氦星的径向速度，发现5颗存在双星运动，并揭示了表面氢丰度与双星性的意外关联，为双星演化和致密天体形成提供了新约束。
中文摘要 AI 辅助
最近在麦哲伦云中发现了一群中等质量氦星（约2-8倍太阳质量），为研究大质量双星演化开辟了新的观测窗口。这些炽热、富氦的恒星被认为是双星相互作用的产物，其中一些恒星的光谱中没有显示出存在发光伴星的证据。在此，我们展示了2018-2023年间利用麦哲伦望远镜上的MagE光谱仪对其中八个系统进行的多历元径向速度（RV）测量结果。五颗氦星表现出与双星运动一致显著的RV变化，而三颗则没有。这五颗具有双星证据的氦星轨道周期从16小时到300天不等，偏心率与零一致，这意味着伴星质量下限约为0.6-2.9倍太阳质量。我们讨论了它们的轨道对不可见伴星性质的影响，发现低质量晚前主序/早主序星（约小于1.5-3.1倍太阳质量）、低质量剥离恒星和致密天体目前都是可行的候选。我们在该样本中发现了一个意外的相关性：表面氢丰度与双星性之间存在关联。双星系统中的氦星是贫氢的（表面氢丰度约0.3-0.4），而没有探测到双星运动的氦星几乎不含氢（表面氢丰度约小于0.05）。这种双峰分布表明，样本中一部分天体较低的RV变化并非仅仅由轨道倾角造成，而是代表了一条截然不同的演化路径。我们考虑了这些天体的三种可能解释：宽距双星、被瓦解的双星和恒星并合。这第一个中等质量氦星样本的双星性质是多样的，为双星演化和致密天体形成提供了重要的经验约束。
英文摘要
The recent discovery of a population of intermediate-mass helium stars ($\sim$2-8 $M_\odot$) in the Magellanic Clouds has opened a new observational window into massive binary evolution. These hot, helium-rich stars are thought to be products of binary interaction, and some show no evidence for a luminous companion in their optical spectra. Here, we present multi-epoch radial velocity (RV) measurements for eight of these systems obtained with Magellan/MagE from 2018-2023. Five helium stars exhibit significant RV variability consistent with binary motion, while three do not. The five helium stars with evidence of binarity have orbital periods from 16 hours to 300 days, and eccentricities consistent with zero, implying companion mass lower limits from $\sim$0.6-2.9 $M_\odot$. We discuss implications of their orbits for the nature of the unseen companions, and find that low-mass late-pre/early-main sequence stars ($\lesssim$1.5-3.1 $M_\odot$), low-mass stripped stars and compact objects are currently viable. We identify an unexpected correlation between surface hydrogen abundance and binarity within this sample: helium stars in binaries are hydrogen-poor ($X_{\rm H,surf}$ $\sim$ 0.3-0.4), whereas helium stars without detected binary motion are nearly hydrogen-free ($X_{\rm H,surf}$ $\lesssim$ 0.05). This bimodality suggests that low RV variability in a subset of the sample is not simply due to inclination, but rather a distinct evolutionary pathway. We consider three possible explanations for these objects: wide binaries, disrupted binaries, and stellar mergers. The binary properties of this first sample of intermediate-mass helium stars is diverse, and provides important empirical constraints for binary evolution and compact object formation.
