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2026 年 4 月 29 日 星期三 · 数据截至 arXiv / ADS 最新收录日
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优先级 5 · 恒星物理 · 疏散星团 · 双星

Evidence for Dynamical Filtering: High Binary Fraction, Hard-binary Excess, and Unresolved Triples in the Surviving Core of NGC 6791

Huanbin Chi, Zhi Li, Feng Wang, et al.

原文摘要Abstract

We present a deep photometric analysis of the main-sequence (MS) population in the old, metal-rich open cluster (OC) NGC 6791 using Gaia Data Release 3 data. After correcting for differential reddening, we use the Bayesian model comparison to test whether stellar rotation can account for the observed MS broadening and find that a rotation-dominated interpretation is strongly disfavored. We therefore infer that unresolved multiplicity is the primary contributor to the photometric offsets. We derive a high-q companion fraction of $54.3\% \pm 2.8\%$ for systems with $q \gtrsim 0.5$, significantly higher than typical values reported for most OCs and the field. The inferred offset distribution is not consistent with a flat mass-ratio distribution but instead shows an excess toward high mass ratios ($q \sim 0.8$--$1.0$), suggestive of preferential survival of hard binaries in a dynamically evolved environment. We also identify a population of stars lying above the equal-mass binary limit ($ΔG > 0.75$ mag), which is difficult to explain with ordinary MS binaries alone and is plausibly interpreted as candidate unresolved triple or higher-order multiple systems. A Kolmogorov--Smirnov test, together with Monte Carlo label-shuffling experiments, shows no statistically significant difference between the projected radial distributions of the single-star and binary/multiple populations within the observed field. Taken together, these results are consistent with the picture that NGC 6791 is the dynamically processed inner remnant of a once more massive cluster.

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证据支持动力学过滤:NGC 6791幸存核心中的高双星比例、硬双星过剩和未分辨三重系统 · 用Gaia DR3数据对NGC 6791主序星进行测光分析,发现未分辨多重性主导光度偏移,高q伴星比例54.3%,并存在未分辨三重系统候选,支持该星团是动力学演化后的致密残余。

预印本 2026-08-14 · 接收 2026-04-29 · 刊出 2026-05-25 · 收录 2026-08-20