极密近双星的形成
The Formation of Very Close Binary Stars
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中文总结 AI 辅助
本文通过测量恒星形成环境中不同类型恒星的极密近双星比例，发现超过85%的晚型和90%以上的大质量极密近双星均通过盘迁移形成，确定盘迁移是主导机制。
中文摘要 AI 辅助
大多数轨道周期P<5天的极密近双星都存在于三星系统中。此前的研究推测，伴星通过Kozai-Lidov周期与潮汐摩擦共同作用，使内双星轨道收缩（硬化）。另一种可能是，该趋势源于共同起源，例如质量更大的分子核和原恒星盘更易碎裂成三星系统，并通过盘迁移将内双星硬化至极短周期，而盘迁移发生在嵌入的I型原恒星阶段，伴星引发的长期演化则发生在长得多的时标上。为确定主导的迁移机制，本文精确测量了恒星形成环境中晚型和早型主星的极密近双星比例。综合五项观测调查后，晚型II/III类T Tauri星的极密近双星比例F_VCB=2.1_{-0.5}^{+1.0}%，与晚型场主序星的测量值（1.7%±0.1%）一致，超过85%的晚型极密近双星在I型原恒星阶段通过盘迁移实现硬化。本文还测量了大麦哲伦云（LMC）中年轻大质量恒星的OGLE-III食双星（EB）比例，大质量年轻恒星天体（YSOs）的极密近食双星比例F_VCEB=8.3_{-3.2}^{+4.9}%、大质量YSOs附近OB星的比例（4.7%±0.8%）、小型年轻H II区中OB星的比例（6.4%±1.5%）彼此一致，且与稍年轻星团中OB星的测量值（4.7%±0.3%）一致，超过90%的大质量极密近双星在嵌入原恒星阶段通过盘迁移实现硬化。
英文摘要
The majority of very close binaries (orbital periods P < 5 days) are in triples. Previous studies surmised that the tertiary hardened the inner binary via Kozai-Lidov cycles coupled with tidal friction. Alternatively, the trend could be due to a common origin, e.g., more massive molecular cores and protostellar disks are more likely to fragment twice into a triple and harden the inner binary to very short periods via disk migration. Disk migration occurs during the embedded Class I protostellar phase while secular evolution with a tertiary occurs on much longer timescales. To determine the dominant migration mechanism, I accurately measure the very close binary fractions of both late-type and early-type primaries in star-forming environments. After combining five surveys, the late-type Class II/III T Tauri very close binary fraction is F_VCB = 2.1_{-0.5}^{+1.0}%, which is consistent with the measurement for late-type field main-sequence stars (1.7% +/- 0.1%). More than 85% of very close late-type binaries hardened via disk migration during the Class I protostellar phase. I next measure the OGLE-III eclipsing binary (EB) fractions of young massive stars in the LMC. The very close EB fractions of massive young stellar objects (YSOs; F_VCEB = 8.3_{-3.2}^{+4.9}%), OB stars near massive YSOs (4.7% +/- 0.8%), and OB stars in small, young H II regions (6.4% +/- 1.5%) are consistent with each other and the measurement for OB stars in slightly older clusters (4.7% +/- 0.3%). More than 90% of very close massive binaries hardened via disk migration during the embedded protostellar phase.
发表机构
- University of Wyoming（怀俄明大学）
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