在α武仙座中检测和测星Ba-Bb子系统：CHARA阵列上的首次双场干涉测量
Detection and Astrometry of the Ba-Bb Subsystem in $α$ Piscium: First Dual-Field Interferometry at the CHARA Array
AI总结：
通过CHARA阵列首次双场干涉测量，确定了α武仙座中Ba-Bb子系统的轨道参数和质量，展示了CHARA在亚秒级双星干涉测量中的新能力。
摘要：
我们展示了CHARA阵列上首次实地演示的双场干涉测量，并首次直接解析了明亮的分层三合星α武仙座中的内Ba-Bb子系统。利用MIRC-X在组件A上进行H波段干涉跟踪，以稳定组件B上的K波段科学干涉条纹，我们检测到一个伴星，其投影分离为7毫弧秒，证实了在B组件中长期怀疑但之前未解析的短周期子系统。近相等的H/K波段通量比表明Ba和Bb接近双F型恒星，与B的光学光谱中看到的两个狭窄线状成分一致。通过结合CHARA干涉测量与存档VLTI/GRAVITY测星和径向速度数据（来自存档和新光谱学（NARVAL和ARCES）），我们推导出一个约束良好的轨道，具有周期P=25天，偏心率e≈0.6，倾角i≈65度，得出精确的动力学质量1.668±0.033M太阳和1.646±0.029M太阳。在0.2至2AU的分离距离上，未检测到额外伴星，至ΔH≈5。我们还获得了宽A-B对的双场差分测星，精度约为0.234毫弧秒，在分离1.85角秒处，误差预算主要由内部延迟线执行器、干涉跟踪性能和色散主导。虽然长周期外轨道未由这些测量进一步细化，但它们与已发表测星轨道的一致性为CHARA双场模式提供了实地验证。这些结果使α Psc成为了一个良好表征的分层系统，适合未来的基准研究，并展示了CHARA在亚秒级双星上的新能力，用于偏轴干涉测量和亚毫弧秒测星。
英文摘要：
We present the first on-sky demonstration of dual-field interferometry at the CHARA Array and the first direct resolution of the inner Ba--Bb subsystem in the bright hierarchical triple $α$ Piscium. Using $H$-band fringe tracking on component A with MIRC-X to stabilize $K$-band science fringes on component B with MYSTIC, we detected a companion at a projected separation of 7 mas, confirming a long-suspected but previously unresolved short-period subsystem within the B component. The nearly equal $H/K$-band flux ratio indicates that Ba and Bb are near-twin F-type stars, consistent with the two narrow-lined components seen in optical spectra of B. By combining CHARA interferometry with archival VLTI/GRAVITY astrometry and radial velocities from archival and new spectroscopy (NARVAL and ARCES), we derive a well-constrained orbit with a period of $P = 25$ d, eccentricity $e \simeq 0.6$, and inclination $i \simeq 65^\circ$, yielding precise dynamical masses of $1.668\pm0.033\,M_\odot$ and $1.646\pm0.029\,M_\odot$. No additional companion is detected down to $ΔH \approx 5$ at separations of 0.2--2 AU. We also obtained dual-field differential astrometry of the wide A--B pair with a precision of ~0.234 mas at a separation of $1.85''$, with an error budget dominated by internal delay-line actuators, fringe-tracking performance and chromatic dispersion. While the long-period outer orbit is not refined by these measurements, their agreement with the published astrometric orbit provides an on-sky validation of the CHARA dual-field mode. These results establish $α$ Psc as a well-characterized hierarchical system suitable for future benchmark studies and demonstrate CHARA's new capability for off-axis interferometry and sub-mas astrometry on arcsecond-scale binaries.
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