The Power of Simultaneous Multi-frequency Observations for mm-VLBI: Beyond Frequency Phase Transfer
Guang-Yao Zhao, Juan Carlos Algaba, Sang-Sung Lee, Taehyun Jung, Richard Dodson, Maria Rioja, Do-Young Byun, Jeffrey Hodgson, Sincheol Kang, Dae-Won Kim, Jae-Yo… 展开作者
Guang-Yao Zhao, Juan Carlos Algaba, Sang-Sung Lee, Taehyun Jung, Richard Dodson, Maria Rioja, Do-Young Byun, Jeffrey Hodgson, Sincheol Kang, Dae-Won Kim, Jae-Young Kim, Jeong-Sook Kim, Soon-Wook Kim, Motoki Kino, Atsushi Miyazaki, Jong-Ho Park, Sascha Trippe, Kiyoaki Wajima
Atmospheric propagation effects at millimeter wavelengths can significantly alter the phases of radio signals and reduce the coherence time, putting tight constraints on high frequency Very Long Baseline Interferometry (VLBI) observations. In previous works, it has been shown that non-dispersive (e.g. tropospheric) effects can be calibrated with the frequency phase transfer (FPT) technique. The coherence time can thus be significantly extended. Ionospheric effects, which can still be significant, remain however uncalibrated after FPT as well as the instrumental effects. In this work, we implement a further phase transfer between two FPT residuals (i.e. so-called FPT-square) to calibrate the ionospheric effects based on their frequency dependence. We show that after FPT-square, the coherence time at 3 mm can be further extended beyond 8~hours, and the residual phase errors can be sufficiently canceled by applying the calibration of another source, which can have a large angular separation from the target (>20 deg) and significant temporal gaps. Calibrations for all-sky distributed sources with a few calibrators are also possible after FPT-square. One of the strengths and uniqueness of this calibration strategy is the suitability for high-frequency all-sky survey observations including very weak sources. We discuss the introduction of a pulse calibration system in the future to calibrate the remaining instrumental effects and allowing the possibility of imaging the source structure at high frequencies with FPT-square, where all phases are fully calibrated without involving any additional sources.
Astrometrically Registered Simultaneous Observations of the 22 GHz H$_2$O and the 43GHz SiO masers towards R Leonis Minoris using KVN and Source/Frequency Phase Referencing
A High-frequency Geodetic VLBI Experiment for Optical Clock Comparison
Institute for Radio Astronomy, National Institute for Astrophysics（射电天文研究所，意大利国家天体物理研究院）；Korea Research Institute of Standards and Science（韩国计量科学研究院）；Quantum Metrology and Nanotechnology division, Istituto Nazionale di Ricerca Metrologica（量子计量与纳米技术部，意大利国家计量研究院）；Korea Astronomy and Space Science Institute（韩国天文学与空间科学研究所）；Dipartimento di Fisica, Universitá di Roma Tor Vergata（罗马托尔维加塔大学物理系）；Korea Institute of Science and Technology Information（韩国科技信息研究所）
Reconstructing Video from Interferometric Measurements of Time-Varying Sources
Massachusetts Institute of Technology（麻省理工学院）；Harvard-Smithsonian Center for Astrophysics（哈佛-史密森天体物理中心）；Massachusetts General Hospital（麻省总医院）；Radboud University（拉德堡德大学）；Google Research（谷歌研究院）
Supermassive black hole binaries in the multi-messenger context of ground and spaceborne VLBI
Delft University of Technology（代尔夫特理工大学）；Joint Institute for VLBI ERIC (JIVE)（甚长基线干涉测量欧洲联合研究所）；Niels Bohr Institute（尼尔斯·玻尔研究所）；Space Telescope Science Institute（太空望远镜科学研究所）；Johns Hopkins University（约翰斯·霍普金斯大学）；Space Initiatives Inc（太空倡议公司）
Evidence of a non-equipartition energy regime in 1803+784 Core-shift and Faraday rotation measurements from simultaneous multi-frequency polarimetric VGOS observations
Observatorio Astronómico Nacional (OAN-IGN)（国家天文台（OAN-IGN））；Centro de Desarrollos Tecnológicos, Observatorio de Yebes (IGN)（技术发展中心，耶贝斯天文台（IGN））；Dpt. Astronomia i Astrofísica, Universitat de València（瓦伦西亚大学天文学与天体物理学系）；Observatori Astronòmic, Universitat de València（瓦伦西亚大学天文台）
VLBI-Enabled Localization of Continuous GW Sources
Kumamoto University（熊本大学）；National Astronomical Observatory of Japan（日本国立天文台）；Yamaguchi University（山口大学）；Kagoshima University（鹿儿岛大学）；Tohoku Institute of Technology（东北工业大学）；National Astronomical Research Institute of Thailand（泰国国立天文研究所）；Tohoku University（东北大学）；Japan Aerospace Exploration Agency（日本宇宙航空研究开发机构）
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）
NIAC project report: Solar system-scale VLBI to dramatically improve cosmological distance measurements
University of Washington（华盛顿大学）；University of Maryland, Baltimore County（马里兰大学巴尔的摩县分校）；NASA/GSFC（美国国家航空航天局戈达德太空飞行中心）；NASA Goddard Space Flight Center（美国国家航空航天局戈达德太空飞行中心）；Oregon State University（俄勒冈州立大学）；California Institute of Technology（加州理工学院）；Massachusetts Institute of Technology（麻省理工学院）
