AI 中文总结
该研究利用昂萨拉双望远镜测量ICRF3源多波段射电流量密度，通过CASA校准数据，分析本地及国际实验，获361个源多频率光变曲线，发现多数源流量密度变化大，新目录能更精确预测信噪比，对天文和大地测量有重要意义。
AI 中文摘要
VLBI全球观测系统（VGOS）是用于大地测量和天体测量的甚长基线干涉测量（VLBI）的下一代系统。为了在大地测量计划中优化每个源的观测时间，需要一个在VGOS频率下观测的源的流量密度目录。这项工作的目的是监测大地测量源在VGOS波段的流量密度。获得的流量密度时间序列可用于更有效地安排大地测量和天体测量VLBI实验，以及探索活动星系核（AGN）物理。昂萨拉双望远镜已被用作单个基线干涉仪来测量国际天体参考系统（ICRF3）中的AGN的流量密度。望远镜同时在3.2、5.5、6.6和10.4GHz进行观测。分析了本地计划的流量监测会话和国际大地测量实验。数据使用通用天文学软件应用程序（CASA）进行校准。还测试了使用测量的流量密度预测大地测量信噪比（S/N）的可能性。已为361个源获得了多达四个频率的同时光变曲线。在测量期间，大多数源的流量密度有显著变化。大多数源具有平坦或反转光谱，只有6%具有陡峭光谱。此外，与标准VGOS流量密度目录相比，这项工作的流量密度更能精确预测大地测量信噪比，特别是对于变化最大的源。为了获得最优化的VGOS计划，需要考虑流量密度变化。这里呈现的流量密度目录预计对天文学和大地测量都有用。我们计划继续监测计划。
英文摘要
The VLBI Global Observing System (VGOS) is the next generation system for geodetic and astrometric Very Long Baseline Interferometry (VLBI). To optimize the observing time for each source in geodetic schedules, a flux density catalog is needed for the sources that are observed at the VGOS frequencies. The aim of this work is to monitor the flux densities of geodetic sources in the VGOS bands. The obtained flux density time series can be used for more effective scheduling of geodetic and astrometric VLBI experiments, as well as probing active galactic nuclei (AGN) physics. The Onsala Twin Telescopes have been used as a single baseline interferometer to measure flux densities of AGN that are part of the International Celestial Reference System (ICRF3). The telescopes observed at 3.2, 5.5, 6.6 and 10.4 GHz simultaneously. Both locally planned flux monitoring sessions and international geodetic experiments were analyzed. The data were calibrated using the Common Astronomy Software Applications (CASA). The possibility of predicting geodetic signal-to-noise ratios (S/N) using the measured flux densities was also tested. Simultaneous light curves in up to four frequencies have been obtained for 361 sources. The majority of the sources vary significantly in flux density during the measurement period. Most sources have a flat or inverted spectrum, with only 6 % having a steep spectrum. Furthermore, the flux densities from this work were shown to more precisely predict geodetic signal-to-noise ratios compared to the standard VGOS flux density catalog, especially for the most variable sources. Flux density variation needs to be taken into account to obtain the most optimal VGOS schedules. The flux density catalog presented here is expected to be of use for both astronomy and geodesy. We plan to continue the monitoring program.
Comments21 pages, 17 figures (including Appendix). Submitted to A&A
