MIRC-X (Michigan InfraRed Combiner-eXeter) is a new highly-sensitive six-telescope interferometric imager installed at the CHARA Array that provides an angular resolution equivalent of up to a 330 m diameter baseline telescope in J and H band wavelengths ($\tfrac{\lambda}{2B}\sim0.6$ milli-arcseconds). We upgraded the original MIRC (Michigan InfraRed Combiner) instrument to improve sensitivity and wavelength coverage in two phases. First, a revolutionary sub-electron noise and fast-frame rate C-RED ONE camera based on a SAPHIRA detector was installed. Second, a new-generation beam combiner was designed and commissioned to (i) maximize sensitivity, (ii) extend the wavelength coverage to J-band, and (iii) enable polarization observations. A low-latency and fast-frame rate control software enables high-efficiency observations and fringe tracking for the forthcoming instruments at CHARA Array. Since mid-2017, MIRC-X has been offered to the community and has demonstrated best-case H-band sensitivity down to 8.2 correlated magnitude. MIRC-X uses single-mode fibers to coherently combine light of six telescopes simultaneously with an image-plane combination scheme and delivers a visibility precision better than 1%, and closure phase precision better than $1^\circ$. MIRC-X aims at (i) imaging protoplanetary disks, (ii) detecting exoplanets with precise astrometry, and (iii) imaging stellar surfaces and star-spots at an unprecedented angular resolution in the near-infrared. In this paper, we present the instrument design, installation, operation, and on-sky results, and demonstrate the imaging and astrometric capability of MIRC-X on the binary system $\iota$ Peg. The purpose of this paper is to provide a solid reference for studies based on MIRC-X data and to inspire future instruments in optical interferometry.

中文翻译：

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MIRC-X：CHARA 阵列上的高灵敏度六望远镜干涉成像仪

MIRC-X（密歇根红外组合器-eXeter）是一种新的高灵敏度六望远镜干涉成像仪，安装在 CHARA 阵列上，可在 J 和 H 波段提供相当于直径 330 m 基线望远镜的角分辨率（$\ tfrac{\lambda}{2B}\sim0.6$ 毫弧秒）。我们升级了原有的 MIRC（密歇根红外组合器）仪器，以提高灵敏度和两个阶段的波长覆盖范围。首先，安装了基于 SAPHIRA 探测器的革命性亚电子噪声和快速帧速率 C-RED ONE 摄像机。其次，设计并启用了新一代光束组合器，以 (i) 最大限度地提高灵敏度，(ii) 将波长覆盖范围扩展到 J 波段，以及 (iii) 实现偏振观测。低延迟和快速帧率控制软件可为 CHARA Array 即将推出的仪器提供高效观测和条纹跟踪。自 2017 年年中以来，MIRC-X 已向社区提供，并展示了低至 8.2 相关幅度的最佳 H 波段灵敏度。MIRC-X 使用单模光纤将六个望远镜的光同时相干组合，采用像平面组合方案，可见度精度优于 1%，闭合相位精度优于 $1^\circ$。MIRC-X 的目标是 (i) 对原行星盘进行成像，(ii) 用精确的天体测量法探测系外行星，以及 (iii) 以前所未有的近红外角分辨率对恒星表面和星斑进行成像。在本文中，我们介绍了仪器的设计、安装、操作和空中结果，并演示 MIRC-X 在双星系统 $\iota$ Peg 上的成像和天体测量能力。本文的目的是为基于 MIRC-X 数据的研究提供可靠的参考，并启发未来的光学干涉测量仪器。