BANANA 项目 VII：高偏心率预示双星中的自旋-轨道错位
The BANANA Project. VII. High Eccentricity Predicts Spin-Orbit Misalignment in Binaries
AI总结：
基于 Gaia DR3 的 2,727 个 F 型主星天体测量双星，研究利用旋转致宽与轨道倾角推断自旋-轨道角，发现偏心率越高错位越显著。
摘要：
双星族群中自旋-轨道对齐的程度可通过测量其轨道倾角和谱线的旋转致宽来确定。正面朝向的双星若处于对齐状态，必然具有较低的旋转致宽；而侧向双星若对齐，则旋转致宽达到最大。相反，如果自旋-轨道角（$ψ$）是随机的，旋转致宽应与轨道倾角无关。利用这一技术，我们研究了来自 Gaia DR3 的 2,727 个天体测量双星样本，这些双星具有 F 型主星，轨道周期介于 50 至 1000 天之间（间距 0.3–2.7 au）。我们发现 $ψ$ 与轨道偏心率 $e$ 密切相关。当 $e<0.15$ 时，平均自旋-轨道角为 $\langleψ\rangle = 6.9_{-4.1}^{+5.4}$ 度；而当 $e>0.7$ 时，该值升至 $\langleψ\rangle = 46_{-24}^{+26}$ 度。这些结果表明，一些双星在形成或演化过程中受到了同时激发轨道偏心率和倾角的过程影响。
英文摘要：
The degree of spin-orbit alignment in a population of binary stars can be determined from measurements of their orbital inclinations and rotational broadening of their spectral lines. Alignment in a face-on binary guarantees low rotational broadening, while alignment in an edge-on binary maximizes the rotational broadening. In contrast, if spin-orbit angles ($ψ$) are random, rotational broadening should not depend on orbital inclination. Using this technique, we investigated a sample of 2{,}727 astrometric binaries from Gaia DR3 with F-type primaries and orbital periods between 50 and 1000 days (separations 0.3--2.7~au). We found that $ψ$ is strongly associated with $e$, the orbital eccentricity. When $e<0.15$, the mean spin-orbit angle is $\langleψ\rangle = 6.9_{-4.1}^{+5.4}$\,degrees, while for $e>0.7$, it rises to $\langleψ\rangle = 46_{-24}^{+26}$\,degrees. These results suggest that some binaries are affected by processes during their formation or evolution that excite both orbital eccentricity and inclination.
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