Subjects: Astronomy submitted time 2024-04-12 Cooperative journals: 《天文学报》
KANG Zhe
NIU Bing-li
LI Zhen-wei
SUN Jian-nan
LV You
ZHU Cheng-wei
DENG Shi-yu
LIU De-long
YANG Wen-bo
ZHANG Nan
LIU Ming
SUN Ming-guo
LIU Cheng-zhi
Abstract： Ground-based optical astronomical telescopes are one of the most important instruments for human exploration and research of the universe. Monitoring and analysis of the optical observation environment of the existing ground-based optical station can provide a reference for the targeted modification of equipment and the adjustment of observation strategies of observers, which is of great significance for improving the observation efficiency of ground-based optical equipment. Jilin Astronomical Observatory (hereinafter referred to as the ``Base'') is located about 5 kilometers (126.3$^{\circ}$ E, 43.8$^{\circ}$ N, 313 meters above sea level) in Nangou, Xiaosuihe Village, Dasuihe Town, Jilin City, Jilin Province, which is affiliated to the Changchun Observatory, National Astronomical Observatories, Chinese Academy of Sciences. The mean value of seeing of the base is about 1.3$''$--1.4$''$, the night sky brightness in the V band near the zenith is 20.64\;mag\,$\cdot$\,arcsec$^{-2}$, and the maximum number of clear nights is better than 270 days per year, which shows the good astronomical observation conditions. Jilin Astronomical Observatory, which was put into operation in 2016, has several photoelectric telescopes, including the 1.2-meter photoelectric telescope, the Mini Optoelectronic Telescope Array, the large field of view photoelectric telescope array, and the advanced multi-functional array-structured photoelectric detector. With the equipments mentioned above, we have carried out relevant research mainly on space target detection and recognition, precision orbit determination, new photoelectric detection methods and multicolor photometry of variables, and so forth. We have maintained a good cooperative relationship with a number of domestic universities and scientific research institutes.
Subjects: Astronomy submitted time 2023-12-15 Cooperative journals: 《天文学报》
Abstract： Hydrogen masters have high short-term stability, using them as master clocks can generate high-precision local standard time in a short period of time. However, the hydrogen maser has a frequency drift phenomenon, which leads to its poor long-term stability, thus affecting the accuracy of the local time. The rotation of the millisecond pulsar is highly stable. With the help of its high long-term stability, it can regularly control the frequency of the hydrogen atomic clock, thus control the real-time signal. The stability of four millisecond pulsars in the second data set released by the International Pulsar Timing Array (IPTA) is analyzed. At the same time, the frequency stability of a hydrogen maser of the National Time Service Center (NTSC) is analyzed by Hadamard variance. Finally, a strategy for steering the frequency of hydrogen master using pulsars is given.
Subjects: Astronomy submitted time 2023-10-07 Cooperative journals: 《天文学报》
Abstract： In order to improve the reliability of the time transfer link, Bureau International des Poids et Mesures (BIPM) has officially taken the Galileo time comparison as the backup link for UTC calculation since 2020. Therefore, the delay calibration of the Galileo signal of the receiver is a necessary work for all time-keeping labs around the world to participate in the UTC link. Taking the GPS link calibrated by Physikalisch-Technische Bundesanstalt (PTB) and the National Time Service Center (NTSC) as a reference, this paper sets PT09 receiver as a reference station to calibrate and verify the total Galileo E3 (Galileo E1\&E5a) delay of NT02 and NT05 receivers of NTSC. The results show that the total Galileo E3 delays of NT02 and NT05 are 74.6\;ns and 46.5\;ns respectively, the calibration uncertainty is 3.5\;ns, and the calibration delay is relatively stable. After calibration, the results of GPS P3 and Galileo E3 common view comparison between NT02 and NT05 receivers of NTSC and calibrated receivers of other time-keeping labs are basically consistent. Taking the comparison results of GPS P3 links between NTP3 and receivers of other labs as a reference, the average deviation is less than 1.5\;ns, which is within the calibration uncertainty.
Subjects: Astronomy >> Astrophysical processes submitted time 2019-05-20 Cooperative journals: 《天文研究与技术》
Abstract：天体光谱数据的智能处理正由传统机器学习方法逐步转向深度学习，主要采用基于计算机视觉的技术手段。本文基于在计算机视觉领域广泛应用的DenseNet网络结构，针对光谱数据进行修改，建立了适用于光谱数据的一维卷积神经网络模型解决天体光谱数据分类任务。在验证数据集上，恒星、星系、类星体的F1分数达到了为0.9987、0.9127、0.9147，高于传统神经网络。光谱分类关注区域的可视化结果表明，本文模型可以学习到各类天体对应的特征谱线，具有较强的可解释性。本文的方法被用于阿里云天池天文数据挖掘大赛——天体光谱智能分类，并在843支参赛队伍的3次数据评比中获得了2次第一、1次第三的成绩，证明了该模型在保证分类精度的同时具有极强的鲁棒性、泛化性，适用于光谱的自动分类。
Subjects: Astronomy >> Astrophysical processes submitted time 2019-04-29 Cooperative journals: 《天文研究与技术》
Abstract： C超丰贫金属星（CEMP）在老年恒星中的普遍存在使得它成为研究宇宙早期形成和演化的重要对象，具有不同中子俘获元素丰度特征的CEMP有着不同的起源。不同于已经历挖掘过程的巨星，主序拐点星能很好地在其表层大气保留形成初期的物质，从而可以追溯到更早期的恒星形成化学环境。我们通过LAMOST巡天数据选源并利用Subaru/HDS进行后续高分辨率光谱观测了12颗CEMP主序拐点星，其中有10颗星是首次被分析。与已有的CEMP主序拐点星观测样本相比，我们的样本中包含了更高比例的中子俘获元素不超丰CEMP恒星（CEMP-no星），发生在中等程度C超丰区域，为其起源研究提供了重要数据。对其中6颗CEMP-no星测定了Li丰度，尤其是其中3颗极贫金属星样为探讨[Fe/H]<-3.0的CEMP拐点星Li丰度特征提供了重要的新观测数据。新增样本验证了CEMP-no星在[Fe/H]～-3.0附近为Li-正常星，与前人结论一致；而新增的两颗CEMP-s星表现出了中等Li丰度，介于之前的较大Li丰度范围，我们的研究为CEMP-s和CEMP-no的分类提供了辅助约束条件。
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