Potential and sky coverage for off-axis fringe tracking in optical long baseline interferometry
Abdelkarim Boskri, Romain G. Petrov, Thami El Halkouj, Massinissa Hadjara, James Leftley, Zouhair Benkhaldoun, Pierre Cruzalèbes, Aziz Ziad, Marcel Carbillet
The spectacular results provided by the second-generation VLTI instruments GRAVITY and MATISSE on active galactic nuclei (AGN) trigger and justify a strong increase in the sensitivity limit of optical interferometers. A key component of such an upgrade is off-axis fringe tracking. To evaluate its potential and limitations, we describe and analyse its error budget including fringe sensing precision and temporal, angular and chromatic perturbations of the piston. The global tracking error is computed using standard seeing parameters for different sites, seeing conditions and telescope sizes for the current GRAVITY Fringe Tracker (GFT) and a new concept of Hierarchical Fringe Tracker. Then, it is combined with a large catalogue of guide star candidates from Gaia to produce sky coverage maps that give the probability to find a usable off-axis guide star in any part of the observable sky. These maps can be used to set the specifications of the system, check its sensitivity to seeing conditions, and evaluate the feasibility of science programs. We check the availability of guide stars and the tracking accuracy for a large set of 15 799 Quasars to confirm the feasibility of a large program on Broad Line Regions in the K band with the GFT and show how it can be extended to the L, M, and N bands. Another set of 331 well-characterized nearby AGNs shows the high potential of MATISSE for imaging and characterization of the dust torus in the N band under off-axis tracking on both Unit Telescopes and Auxiliary Telescopes.
Astrometry in two-photon interferometry using Earth rotation fringe scan
光学干涉仪可能不需要站之间的相位稳定的光学链路，如果可以向它们提供量子力学纠缠对的源，从而实现长基线。我们开发了这个想法的一个新的变体，提出来自两个不同天文源的光子可以在两个解耦的站进行干涉。然后可以在后处理中计算干扰产物，或者只需要站之间的缓慢的经典连接。在这项工作中，我们研究了这种方法的实际可行性。我们发展了一种地球自转条纹扫描技术的贝叶斯分析方法，并表明在高信噪比的限制下，它再现了从一个简单的Fisher矩阵分析的结果。我们确定在北半球，这种技术可以应用的候选人楼梯对。使用两台有效收集面积为$\sim 2$ m $^2$的望远镜，我们可以在几个小时的观测中检测到边缘，并测量$\sim 10\,μ$源的天体测量分离，与以前的估计一致。
Stellar interferometry with a K-band integrated optics beam combiner instrument at the CHARA Array - I. First on-sky fringes for CHARIOT
Corning Optical Communications GmbH & Co. KG（康宁光学通讯有限公司）；Leibniz-Institut für Astrophysik Potsdam（波茨坦阿斯特罗物理学会莱布尼茨研究所）；I. Physikalisches Institut, Universität zu Köln（科隆大学第一物理研究所）；The CHARA Array of Georgia State University（佐治亚州立大学CHARA阵列）；Institute of Photonics and Quantum Sciences, Heriot-Watt University（赫瑞-瓦特大学光子与量子科学研究所）；Humboldt-Universität zu Berlin（柏林洪堡大学）
Detection and Astrometry of the Ba-Bb Subsystem in $α$ Piscium: First Dual-Field Interferometry at the CHARA Array
The CHARA Array of Georgia State University（佐治亚州立大学查拉阵列）；European Organisation for Astronomical Research in the Southern Hemisphere (ESO)（欧洲南方天文台）；Université Côte d’Azur, Observatoire de la Côte d’Azur, CNRS（蔚蓝海岸大学蔚蓝海岸天文台法国国家科学研究中心）；Department of Astronomy, University of Michigan（密歇根大学天文学系）；Center for High Angular Resolution Astronomy and Department of Physics and Astronomy, Georgia State University（佐治亚州立大学高分辨率天体测量中心及物理与天文学系）；Astrophysics Group, Department of Physics & Astronomy, University of Exeter（埃克塞特大学物理与天文学系天体物理学组）
