基于SRT数据的天文光谱通量密度校准器验证新方法

A. N. Ermakov, Y. Kovalev, V. Vasilkov, V. Soglasnov, M. Lisakov, Y. Kovalev
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引用次数: 0

摘要

RadioAstron是一项国际项目,在波长为92、18、6.2和1.35厘米的地面空间VLBI。SRT有一个直径10米的抛物面天线。它于2011年7月18日发射,并与许多地面射电望远镜一起飞行至2019年1月10日。VLBI的基地达到了25万公里。本文介绍了用射电天空间射电望远镜(SRT)对辐射观测数据进行大量处理的结果。设计了一种新的用于单望远镜模式下SRT校准过程自动化处理的复合体。在2015-2019年4年SRT飞行的校准时段中,分别对6.2、18和92 cm波长范围内的主、备用噪声信号源作为次级校准标准,相对于已知的主通量密度标准源仙后座A (cassiopia -A)和蟹状星云(Crab)进行了校准。校正使用1977年普遍接受的光谱通量密度标度。处理的最重要和意想不到的结果之一是检测到相对于Crab和Cas a的噪声产生器校准之间存在25-35%的差异。分析表明,这种差异的原因是Cas a和Crab的真实长期变率,这与1977年标准尺度下已知的外推通量密度不对应。从1977年普遍接受的通量密度尺度到2017年和2014年的新修正尺度的过渡消除了所发现的差异。在此基础上,提出了一种新的天文光谱通量密度校准器校验方法。使用望远镜的噪声发生器作为指示器。SRT校准示例扩展到大多数地基射电望远镜,也可能包括RATAN-600。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
A new Method for Verification of Astronomical Spectral Flux Density Calibrators based on SRT Data
The RadioAstron is an international project of a ground-space VLBI at the wavelengths 92, 18, 6.2 and 1.35 cm. The SRT has a paraboloid antenna with a 10 m diameter. It had been launched on July 18, 2011 and worked in flight up to January 10, 2019 together with many ground-based radio telescopes. The base of the VLBI reached 250 000 km. The results of mass processing of radiometric observations obtained with the RadioAstron Space Radio Telescope (SRT) are presented. A new complex for automated processing of SRT calibration sessions in the single telescope mode has been designed. The main and backup noise signal generators as secondary calibration standards in the wavelength ranges of 6.2, 18 and 92 cm in the calibration sessions for the 4 years of SRT flight in 2015–2019 are calibrated relative to the known primary flux density standard sources - Cassiopeia-A (Cas A) and the Crab Nebula (Crab). Calibration was carried out using the 1977 generally accepted spectral flux density scale. One of the most important and unexpected results of processing is the detection of a 25–35% discrepancy between the noise generator calibrations relative to Crab and Cas A. The analysis showed that the reason for this discrepancy is a real long-term variability of Cas A and Crab, which does not correspond to the known extrapolated flux densities in the standard scale of 1977. The transition from the generally accepted flux density scale of 1977 to the new corrected scales of 2017 and 2014 eliminates the discrepancy found. Based on the analysis above the report proposes a new method for verifying astronomical spectral flux density calibrators. A noise generator of a telescope is used as an indicator. The SRT calibration example is extended to most ground-based radio telescopes, also possibly including the RATAN-600.
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