First light for GRAVITY: Phase referencing optical interferometry for the Very Large Telescope Interferometer
First light for GRAVITY: Phase referencing optical interferometry for the Very Large Telescope Interferometer
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DOI：
10.1051/0004-6361/201730838
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发表时间：
2017-05
影响因子：
6.5
通讯作者：
G. C. R. Abuter;M. Accardo;A. Amorim;N. Anugu;G. Ávila;N. Azouaoui;M. Benisty;J. Berger;N. Bl
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文献类型：
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作者：
G. C. R. Abuter;M. Accardo;A. Amorim;N. Anugu;G. Ávila;N. Azouaoui;M. Benisty;J. Berger;N. Bl
GRAVITY是一种新仪器，将欧洲南方天文台甚大望远镜干涉仪的光线相干组合，形成等效直径130 m角分辨率、收集面积200 m2的望远镜。该仪器包括光纤馈送集成光学光束组合、高分辨率光谱、内置光束分析和控制、近红外波前传感、相位跟踪、双光束操作和激光计量。 GRAVITY 为光学/红外干涉测量、相位参考成像和窄角天体测量技术开辟了道路，在许多方面都遵循无线电干涉测量的概念。本文概述了 GRAVITY 并报告了 2015/2016 年调试期间的性能和首次天文观测。我们展示了对 mK ≈ 10 mag 的微弱恒星的相位跟踪，对比 mK ≈ 15 mag 更暗的物体进行相位参考干涉测量，极限星等为 mK ≈ 17 mag，微小的长相干积分，可见度精度优于 0.25%，光谱微分相位和闭合相位精度优于 0.5°，对应于优于 10 的微分天体测量精度 微角秒 (μas)。双光束天体测量法利用激光计量技术测量两个物体的相位差，目前仍在调试中。首次观察显示，在几个月内跟踪物体时，残差低至 50 μas。我们通过对不同仪器模式下典型物体的观察来说明仪器性能。例子包括用于相位参考双光束观测和红外波前传感的银心超大质量黑洞及其快速轨道恒星S2、用于几μas光谱微分天体测量的高质量X射线双星BP Cru和PDS 456的活动星系核、用于光谱微分可见度分析的T Tauri星S CrA、用于高精度的Ψ Tel和24 Cap 能见度观测，以及用于重力干涉成像的 η Car。
GRAVITY is a new instrument to coherently combine the light of the European Southern Observatory Very Large Telescope Interferometer to form a telescope with an equivalent 130 m diameter angular resolution and a collecting area of 200 m2. The instrument comprises fiber fed integrated optics beam combination, high resolution spectroscopy, built-in beam analysis and control, near-infrared wavefront sensing, phase-tracking, dual-beam operation, and laser metrology. GRAVITY opens up to optical/infrared interferometry the techniques of phase referenced imaging and narrow angle astrometry, in many aspects following the concepts of radio interferometry. This article gives an overview of GRAVITY and reports on the performance and the first astronomical observations during commissioning in 2015/16. We demonstrate phase-tracking on stars as faint as mK ≈ 10 mag, phase-referenced interferometry of objects fainter than mK ≈ 15 mag with a limiting magnitude of mK ≈ 17 mag, minute long coherent integrations, a visibility accuracy of better than 0.25%, and spectro-differential phase and closure phase accuracy better than 0.5°, corresponding to a differential astrometric precision of better than ten microarcseconds (μas). The dual-beam astrometry, measuring the phase difference of two objects with laser metrology, is still under commissioning. First observations show residuals as low as 50 μas when following objects over several months. We illustrate the instrument performance with the observations of archetypical objects for the different instrument modes. Examples include the Galactic center supermassive black hole and its fast orbiting star S2 for phase referenced dual-beam observations and infrared wavefront sensing, the high mass X-ray binary BP Cru and the active galactic nucleus of PDS 456 for a few μas spectro-differential astrometry, the T Tauri star S CrA for a spectro-differential visibility analysis, ξ Tel and 24 Cap for high accuracy visibility observations, and η Car for interferometric imaging with GRAVITY.