The third realization of the International Celestial Reference Frame by very long baseline interferometry
P. Charlot, C. S. Jacobs, D. Gordon, S. Lambert, A. de Witt, J. Böhm, A. L. Fey, R. Heinkelmann, E. Skurikhina, O. Titov, E. F. Arias, S. Bolotin, G. Bourda, C.… 展开作者
P. Charlot, C. S. Jacobs, D. Gordon, S. Lambert, A. de Witt, J. Böhm, A. L. Fey, R. Heinkelmann, E. Skurikhina, O. Titov, E. F. Arias, S. Bolotin, G. Bourda, C. Ma, Z. Malkin, A. Nothnagel, D. Mayer, D. S. MacMillan, T. Nilsson, R. Gaume
A new realization of the International Celestial Reference Frame (ICRF) is presented based on the work achieved by a working group of the International Astronomical Union (IAU) mandated for this purpose. This new realization, referred to as ICRF3, is based on nearly 40 years of data acquired by very long baseline interferometry. The ICRF3 includes positions at 8.4 GHz for 4536 sources, supplemented with positions at 24 GHz for 824 sources and at 32 GHz for 678 sources, for a total of 4588 sources. A subset of 303 sources among these, uniformly distributed on the sky, are identified as "defining sources" and as such serve to define the axes of the frame. Source positions are reported for epoch 2015.0 and must be propagated for observations at other epochs for the most accurate needs, accounting for the acceleration toward the Galactic center, which results in a dipolar proper motion field of amplitude 0.0058 milliarcsecond/yr (mas/yr). The frame shows a median positional uncertainty of about 0.1 mas in right ascension and 0.2 mas in declination, with a noise floor of 0.03 mas in the individual source coordinates. A subset of 500 sources is found to have extremely accurate positions at 8.4 GHz, in the range of 0.03 to 0.06 mas. Comparing ICRF3 with the Gaia Celestial Reference Frame 2 in the optical domain, there is no evidence for deformations larger than 0.03 mas between the two frames. Significant positional offsets between the three ICRF3 frequencies are detected for about 5% of the sources. Moreover, a notable fraction (22%) of the sources shows optical and radio positions that are significantly offset. There are indications that these positional offsets may be the manifestation of extended source structures. This third realization of the ICRF was adopted by the IAU at its 30th General Assembly in August 2018 and replaced the previous realization, ICRF2, on January 1, 2019.
The Celestial Reference Frame at K Band: The CRF-K-2025 Catalog
U.S. Naval Observatory（美国海军天文台）；South African Radio Astronomy Observatory (SARAO)（南非射电天文观测台）；Jet Propulsion Laboratory, California Institute of Technology/NASA（加州理工学院/美国国家航空航天局喷气推进实验室）；TU Wien, Department of Geodesy and Geoinformation（维也纳工业大学大地测量与地理信息系）；German Space Agency within DLR（德国航空航天中心下属德国航天局）；University of Tasmania（塔斯马尼亚大学）；Observatorio Astronómico Nacional, IGN, Spain（西班牙国家地理研究所国家天文台）；Korea Astronomy and Space Science Institute, Korea（韩国天体宇宙科学研究所）；Sejong University, Korea（韩国世宗大学）
VLBI astrometry of radio stars to link radio and optical celestial reference frames - II. 11 radio stars
Shanghai Astronomical Observatory, Chinese Academy of Sciences（中国科学院上海天文台）；University of Chinese Academy of Sciences（中国科学院大学）；Department of Geodesy and Geodynamics, Finnish Geospatial Research Institute (FGI), National Land Survey of Finland（芬兰国家土地测量局芬兰地理研究所大地测量与地球动力学系）；Korea Astronomy and Space Science Institute（韩国天体物理与空间科学研究所）；University of Helsinki（赫尔辛基大学）；Harvard-Smithsonian Center for Astrophysics（哈佛-史密森尼天体物理中心）
Absolute Motion of the Infrared Counterpart to Sagittarius A* in the Gaia Celestial Reference Frame 3 and Limits on an Intermediate-mass Black Hole Companion
University of California, Los Angeles（加州大学洛杉矶分校）；University of Nevada, Reno（内华达大学里诺分校）
Beyond Sgr A* and M87*: Sub-Microarcsecond Black Hole Shadow Detection via Lunar-based Extremely Long Baseline Interferometry
Shanghai Astronomical Observatory, Chinese Academy of Sciences（中国科学院上海天文台）；Key Laboratory of Radio Astronomy and Technology, Chinese Academy of Sciences（中国科学院射电天文与技术重点实验室）；Max-Planck-Institut für Radioastronomie（马克斯·普朗克射电天文研究所）；Tsung-Dao Lee Institute, Shanghai Jiao Tong University（上海交通大学李政道研究所）；School of Physics and Astronomy, Shanghai Jiao Tong University（上海交通大学物理与天文学院）；Institut für Theoretische Physik, Goethe-Universität（法兰克福大学理论物理研究所）
Gaia Data Release 1: The reference frame and the optical properties of ICRF sources
作为Gaia DR 1数据处理的一部分，计算了一个特殊的天体测量解，即所谓的辅助类星体解。这给出了选定的河外天体的位置，包括国际天体参考系（ICRF 2）第二次实现中的射电源，这些射电源具有足够明亮的光学对应物，可以与盖亚一起观察。这些位置的子集用于将Gaia DR 1的位置参考系与ICRF 2对齐。我们描述的盖亚辅助类星体的解决方案的一个子集的源匹配ICRF 2的属性，并比较它们的光学和无线电的位置在亚质量水平。50%的源的形式标准误差优于0.76毫角秒（mas），90%的源的形式标准误差优于3.35毫角秒。光学星等是在盖亚未过滤的光度G波段获得的。与定义源的无线电位置的比较表明，系统差异不大于零点几个mas。有问题的解决方案的分数，不容易占统计，是小于6%。标准化的差异延长了尾部，需要对大约100个源进行逐案调查，但我们还没有看到任何与源中的光无线电偏移有关的差异。
