通过吞噬亚恒星伴星形成亚矮B星的研究
On the formation of subdwarf B stars via engulfment of substellar companions I. Conditions for and occurrence of envelope ejection events
浏览论文内容
中文总结 AI 辅助
该研究采用能量平衡方法，模拟亚恒星伴星轨道演化，确定吞噬抛射sdB星包层的条件，结合观测伴星分布估算发生率，为相关流体模拟提供指导。
中文摘要 AI 辅助
亚矮B（sdB）星形成的经典场景涉及在红巨星支（RGB）顶端附近抛出行星状天体的包层，同时启动核心氦燃烧。尽管已知双星相互作用主导着sdB星的形成，但看似单颗的sdB星的起源仍不确定。我们采用能量平衡方法，研究sdB星的前身星通过吞噬亚恒星伴星抛射出包层的条件，并进一步估算通过该通道形成的sdB星的占比。我们模拟亚恒星伴星在亚巨星阶段和RGB阶段的轨道演化，以确定吞噬的起始点，并计算在恒星包层内螺旋过程中释放的能量。通过将该能量与包层的结合能进行比较，并探索其沉积的不同效率，我们确定了包层抛射所需的条件。随后，我们将这些结果与观测到的亚恒星伴星族群相结合，估算sdB星形成的发生率。亚恒星天体的吞噬可在质量-半长轴参数空间的有限区域内导致包层抛射，该区域的范围取决于宿主恒星的属性和能量转移效率。抛射所需的最小伴星质量随效率降低和恒星质量增加而增大。因此，包层抛射的频率受亚恒星伴星分布的强烈影响，尤其是受褐矮星沙漠中天体稀缺性的影响。低质量褐矮星和大质量行星是解释看似单颗的sdB星存在的可行候选体。我们的结果确定了该机制在能量上可行的参数空间区域，并为未来的多维流体动力学模拟提供了指导。
英文摘要
The canonical scenario for the formation of subdwarf B (sdB) stars involves the ejection of the progenitor's envelope near the tip of the Red Giant Branch (RGB), concurrent with the onset of core He-burning. While binary interactions are known to dominate sdB formation, the origin of apparently single sdB stars remains uncertain. We investigate the conditions under which an sdB progenitor can eject its envelope through the engulfment of a substellar companion, using an energy balance approach. We simulate the orbital evolution of substellar companions during the subgiant and RGB phases of their host stars (1.2-2.0 M_Sun) to determine the onset of engulfment and calculate the energy released during inspiral within the stellar envelope. By comparing this energy with the envelope binding energy and exploring different efficiencies for its deposition, we identify the conditions required for envelope ejection. We then estimate the occurrence of such events using observed population of substellar companions. The engulfment of substellar objects can lead to envelope ejection within a limited region of the mass-semi-major axis parameter space, whose extent depends on the host star's properties and energy transfer efficiency. The minimum companion mass required for ejection increases with decreasing efficiency and increasing stellar mass. As a result, the frequency of envelope ejection is strongly influenced by the distribution of substellar companions, particularly by the paucity of objects in the brown-dwarf desert. The engulfment of low-mass brown dwarfs and massive planets during the late RGB can provide sufficient energy to eject the stellar envelope, which could ultimately lead to the formation of sdB stars. Our results define the region of parameter space where this mechanism is energetically possible and provide a guide for future multidimensional hydrodynamical simulations.
发表机构
- Space sciences, Technologies and Astrophysics Research (STAR) Institute, Université de Liège（列日大学空间科学、技术与天体物理研究研究所）
- Institut d’Astronomie et d’Astrophysique, Université Libre de Bruxelles (ULB)（布鲁塞尔自由大学天文与天体物理研究所）
机构由 AI 辅助整理，请以论文原文为准。
