Subjects: Astronomy submitted time 2023-12-13 Cooperative journals: 《天文学进展》
Abstract: In recent years, many cases of the quasi-periodic oscillation penomenon have been discovered in the light curves of active galactic nuclei, and the study may provide a particularly useful way to explore the physics of the supermassive black holes in the center. We collect these reported quasi-periodic oscillation cases in different bands, and summarize them in this paper. Based on the collected cases, we discuss their overall characteristics, among which the detected periods have a strong observational selection effect and there are few cases with high significance so far. We briefly discuss the mechanisms for producing quasi-periodic oscillations currently under consideration, most of which are related to the Lenense -Thirring effect or binary nature of the central black hole systems. We believe that a large number of quasi-periodic oscillations will be discovered in the near future with the launch of various large-survey programs at different wavelength bands.
Subjects: Astronomy >> Astrophysical processes submitted time 2023-01-17 Cooperative journals: 《天文研究与技术》
Abstract: The purpose of this design is to realize the digital temperature control of the hydrogen maser. Is based on the basic principle of temperature detection and control design of a two-stage temperature control system (including the hydrogen maser inside the furnace and the furnace), the temperature control system is mainly composed of bridge circuit, analog-to-digital conversion circuit, temperature calculation and PID (proportional integral differential) control system, PWM (pulse width modulation) output circuit, heating wire. When the ambient temperature fluctuates from 21℃ to 25℃, the digital temperature control system achieves the temperature stability of 0.002℃, which proves the feasibility of the digital board to control the temperature of the hydrogen maser.
Subjects: Astronomy >> Astrophysical processes submitted time 2022-10-17 Cooperative journals: 《天文研究与技术》
Abstract: In order to reduce the relative change rate of the transition frequency of the hydrogen masers caused by the inhomogeneous C field, two designs of C field components, three-segment solenoids and four sets of coils, are proposed. Using the high-order expansion of the magnetic field on the axis, the ampere-turn ratio and the solenoid spacing were calculated when the three-segment solenoid with L=0.05-0.5 constructed a uniform magnetic field. The finite element analysis of the magnetic field is carried out with L=0.2-0.45, and the magnetic field non-uniformity distribution with different widths is given. Among them, the maximum non-uniformity with L=0.45 in the storage bubble area is 0.105%, and the corresponding relative change rate of transition frequency is1.02×10-13 . Using the same method, the ampere-turn ratio and spacing between coils when four or five sets of coils construct a uniform magnetic field are calculated, and the finite element simulation of the magnetic field in the coil is carried out, and the non-uniformity distribution is given. The maximum non-uniformity of the magnetic field in the storage bubble region in the four sets of coils is 0.066%, and the corresponding transition frequency relative change rate is 6.42×10-14
Subjects: Astronomy >> Astrophysical processes submitted time 2022-06-24 Cooperative journals: 《天文研究与技术》
Abstract:天马13 m 射电望远镜是新一代专为空间大地测量的VLBI天线,即所谓的VGOS系统。VGOS观测将从调度、相关、观测策略到分析各个方面改变VLBI。与传统测地观测相比,VGOS观测将数据提高1-2个数量级。天马13 m天线安装有3~15Ghz宽频制冷接收机,一般要求天线指向偏差小于最高频率波束宽度的1/10。为了满足高精度指向要求,本文详细介绍了指向建立的方法和天线控制扫描策略,给出了系统误差修正模型的完全表达式,明确了指向修正模型中的参数意义。基于该天线指向扫描的实测数据,实测评估了该望远镜的指向精度。采用最小二乘法对覆盖全天区的数据样本进行拟合,得到天马13 m射电望远镜指向模型,并加载到天线伺服控制系统中进行验证,得到了好于10"的的盲指误差。
Subjects: Astronomy >> Astrophysical processes submitted time 2017-09-26 Cooperative journals: 《天文研究与技术》
Abstract:谱线观测是上海天文台65 m射电望远镜的主要观测手段之一,在和美国国家射电天文台联合研制脉冲星和谱线观测终端的基拙上,开发了观测控制软件,设计了流量定标的硬件和软件,开发了频率校准程序。经过大量的观测测试,证明观测和数据校准系统的有效性,并于2015年下半年对国内用户开放,取得了大量的观测结果。详细介绍本终端的组成和功能,观测控制软件的流程,结合观测数据介绍流量定标和频率校准的处理方法和结果,并给出下一步的工作计划。
Subjects: Astronomy >> Astrophysical processes submitted time 2017-09-26 Cooperative journals: 《天文研究与技术》
Abstract:天马望远镜Ka波段宽带接收机是研究恒星形成、星际介质以及深空探测的重要观测平台。论述了接收机核心器件Ka波段宽带圆极化器的研制过程。该器件由90°两壁波纹移相器和改进型双脊波导形式的正交模式藕合器构成,工作频带为26.5 ~40 GHz,相对带宽达到41%。首先介绍了圆极化器的应用背景及工作原理,继而进行模型设计和仿真优化,最后进行结构设计和样品实测。实测结果显示,移相器的相移误差为904°,轴比达到0. 6 dB,正交模式藕合器的交又极化为-26 dB ,隔离度为-35 dB ,器件端口驻波均低于-18 dB,实测结果与设计仿真相符。
Subjects: Astronomy >> Astrophysical processes submitted time 2017-09-26 Cooperative journals: 《天文研究与技术》
Abstract:消除综合孔径望远镜子孔径之间的相对光程差是实现高分辨率干涉成像的前提条件,条纹检测法是一种检测相对光程差的有效办法。因子孔径的空间位置排布使干涉条纹具有一定的方向性,若不能精确获知干涉条纹的角度,则无法沿条纹的法线方向行采样,进而无法根据对比度变化曲线的最大值获得子孔径之间的最小光程差位置。提出了一种基于傅里叶变换和图像二值化闺值遍历的获得干涉条纹角度的方法,首先介绍了算法的基本原理,其次通过对条纹角度为43。的仿真数据进行算法验证得到的角度为43. 007 8 0,与理论值的误差为0. 018%,证实了方法的可行性。最后对比了未旋转相机和旋转相机两种情况下的条纹对比度变化曲线,可知通过旋转相机使条纹转至相机靶面纵轴方向再进行采样的办法,更有利于精确得到相对光程差的最小位置。
Subjects: Astronomy >> Astrophysical processes submitted time 2017-09-26 Cooperative journals: 《天文研究与技术》
Abstract:海量观测数据及次生数据的高效存储与检索,天文大数据的快速及时处理,加速天文学研究的科学产出等问题,已成为天文观测和天文研究迫切需要解决的难题。以信息技术为支撑的天文大数据的高效分析和处理,帮助天文学家重新审视和了解宇宙。虚拟天文台的出现为全球范围内研究资源的无缝透明连接提供了协议、标准,以协议为基拙规范了天文数据的发布与检索方式。以国内外现有的观测设备为基拙,综述目前主流天文机构的数据发布与检索相关情况。
Subjects: Astronomy >> Astrophysical processes submitted time 2017-09-26 Cooperative journals: 《天文研究与技术》
Abstract:随着数据记录速率的提高以及对数据准确性的要求,老的采集系统已经不能满足新的要求,迫切要求采用新的终端和技术。Mark6是麻省理工学院研制的最新的记录终端,已经用于主要的天文机构,比如JIVE, KASI, Max-Planck-Institute等。首先介绍了VLBI数据记录终端的现状,给出了上海天文台对Mark6软硬件的调试与配置;然后介绍了使用Mark6与CDAS2互连进行数据记录的测试及分析;最后对Mark6系统的应用及相关软件的后续研发进行了简洁阐述。可为后续终端采集系统的安装、配置及升级提供指导及参考。