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Lijiang 2.4-meter Telescope and its instruments

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Research in Astronomy and Astrophysics 2019年第10期19卷 95-108页

作者： Chuan-Jun Wang Jin-Ming Bai Yu-Feng Fan Ji-Rong Mao Liang Chang Yu-Xin Xin Ju-Jia Zhang Bao-Li Lun Jian-Guo Wang Xi-Liang Zhang Mei Ying Kai-Xing Lu Xiao-Li Wang Kai-Fan Ji Ding-Rong Xiong Xiao-Guang Yu Xu Ding Kai Ye Li-Feng Xing Wei-Min Yi Liang Xu Xiang-Ming Zheng Yuan-Jie Feng Shou-Sheng He Xue-Li Wang Zhong Liu Dong Chen Jun Xu Song-Nian Qin Rui-Long Zhang Hui-Song Tan Zhi Li Ke Lou Jian Li Wei-Wei Liu Yunnan Observatories Chinese Academy of SciencesKunming 650216China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming 650216 China Center for Astronomical Mega-Science Chinese Academy of Sciences Beijing 100101 China University of Chinese Academy of Sciences Beijing 100049 China Astrophysics Center of Guangzhou University Guangzhou 510006China

The Lijiang 2.4-meter Telescope(LJT), the largest common-purpose optical telescope in China,has been available to the worldwide astronomical community since 2008. It is located at the Gaomeigu site,Lijiang Observatory(LJO), in the southwest of China. The site has very good observational *** its 10-year operation, several instruments have been equipped on the LJT. Astronomers can perform both photometric and spectral observations. The main scientific goals of LJT include recording photometric and spectral evolution of supernovae, reverberation mapping of active galactic nuclei, investigating the physical properties of binary stars and near-earth objects(comets and asteroids), and identification of exoplanets and all kinds of transients. Until now, the masses of 41 high accretion rate black holes have been measured, and more than 168 supernovae have been identified by the LJT. More than 190 papers related to the LJT have been published. In this paper, the general observation conditions of the Gaomeigu site is introduced at first. Then, the structure of the LJT is described in detail, including the optical, mechanical, motion and control system. The specification of all the instruments and some detailed parameters of the YFOSC is also presented. Finally, some important scientific results and future expectations are summarized.

关键词： telescopes Lijiang 2.4-m Telescope-instrumentation photometers-instrumentation spectrographs

Generalized split monopole magnetospheres: The effects of current sheets

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arXiv 2020年

We show that energy should be dissipated or extracted in the current sheet (CS) of a split magnetosphere deviating from the Michel split monopole, with the CS heating up or cooling down. But the electromagnetic energy remains unchanged everywhere. Based on the de-centered monopole solution generated by symmetry in flat spacetime, we construct two generalized split monopole configurations, in which the field lines intersect with the CS at arbitrary angles. One configuration resembles the outer geometry of the so-called "new pulsar magnetosphere model", for which up to 47% of the spin down energy is transferred to the Joule heating process in the CS. In the other configuration, we observe that negative energy is dissipated in the CS, which is usually observed in magnetospheres on rotating black holes. This means that energy is extracted simultaneously from the central star and the CS to power the output Poynting flux at infinity. We interpret the extraction of energy from the CS as that thermal energy of charged particles in the CS is transferred to the ordered kinetic energy of these particles drifting in the force-free (FF) electromagnetic fields. Hence, the CS is like an "air conditioner" in the sky, which can heat up or cool down, depending on the configurations. Copyright © 2020, The Authors. All rights reserved.

关键词： Kinetics

Time varying Na i D absorption in ILRTs as a probe of circumstellar material

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arXiv 2023年

作者： Byrne, R.A. Fraser, M. Cai, Y.-Z. Reguitti, A. Valerin, G. School of Physics University College Dublin Belfield Dublin 4 Ireland Yunnan Observatories Chinese Academy of Sciences Kunming650216 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650216 China Instituto de Astrofìsica Departamento de Ciencias Fisicas Universidad Andres Bello Fernandez Concha 700 Las Condes Santiago8320000 Chile Nuncio Monsenor Sòtero Sanz 100 Providencia Santiago8320000 Chile INAF — Osservatorio Astronomico di Padova Vicolo dell’Osservatorio 5 Padova35122 Italy Dipartimento di Fisica e Astronomia "G. Galilei" Università degli studi di Padova Vicolo dell’Osservatorio 3 PadovaI-35122 Italy

Intermediate-Luminosity Red Transients (ILRTs) are a class of observed transient posited to arise from the production of an electron-capture supernova from a super-asymptotic giant branch star within a dusty cocoon. In this paper, we present a systematic analysis of narrow Na i D absorption as a means of probing the circumstellar environment of these events. We find a wide diversity of evolution in ILRTs in terms of line strength, time-scale, and shape. We present a simple toy model designed to predict this evolution as arising from ejecta from a central supernova passing through a circumstellar environment wherein Na ii is recombining to Na i over time. We find that while our toy model can qualitatively explain the evolution of a number of ILRTs, the majority of our sample undergoes evolution more complex than predicted. The success of using the Na i D doublet as a diagnostic tool for studying circumstellar material will rely on the availability of regular high-resolution spectral observations of multiple ILRTs, and more detailed spectral modelling will be required to produce models capable of explaining the diverse range of behaviours exhibited by ILRTs. In addition, the strength of the Na i D absorption feature has been used as a means of estimating the extinction of sources, and we suggest that the variability visible in ILRTs would prevent such methods from being used for this class of transient, and any others showing evidence of variability. © 2023, CC BY.

关键词： Supernovae

On the injection of relativistic electrons in the jet of 3C 279

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arXiv 2020年

作者： Hu, Wen Yan, Dahai Dai, Benzhong Zeng, Wei Hu, Qianglin College of Mathematics and Physics Jinggangshan University Jiangxi Province Jian343009 China Key Laboratory for the Structure and Evolution of Celestial Objects Yunnan Observatory Chinese Academy of Sciences Kunming650011 China Department of Astronomy Key Laboratory of Astroparticle Physics Yunnan Province Yunnan University Kunming650091 China

The acceleration of electrons in 3C 279 is investigated through analyzing the injected electron energy distribution (EED) in a time-dependent synchrotron self-Compton + external Compton emission model. In this model, it is assumed that relativistic electrons are continuously injected into the emission region, and the injected EED [Q′e(γ′)] follows a single power-law form with low- and high-energy cutoffs γmin′ and γmax′, respectively, and the spectral index n, i.e, Q′e(γ′) ∝ γ′−n. This model is applied to 14 quasi-simultaneous spectral energy distributions (SEDs) of 3C 279. The Markov Chain Monte Carlo fitting technique is performed to obtain the best-fitting parameters and the uncertainties on the parameters. The results show that the injected EED is well constrained in each state. The value of n is in the range of 2.5 to 3.8, which is larger than that expected by the classic non-relativistic shock acceleration. However, the large value of n can be explained by the relativistic oblique shock acceleration. The flaring activity seems to be related to an increased acceleration efficiency, reflected in an increased γmin′ and electron injection power. Copyright © 2020, The Authors. All rights reserved.

关键词： Gamma rays

A new fast Monte Carlo code for solving radiative transfer equations based on Neumann solution

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arXiv 2021年

作者： Xiao-Lin, Yang Jian-Cheng, Wang Chu-Yuan, Yang Yunnan Observatories Chinese Academy of Sciences 396 Yangfangwang Guandu District Kunming650216 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences 396 Yangfangwang Guandu District Kunming650216 China Center for Astronomical Mega-Science Chinese Academy of Sciences 20A Datun Road Chaoyang District Beijing100012 China University of Chinese Academy of Sciences Beijing100049 China

In this paper, we proposed a new Monte Carlo radiative transport (MCRT) scheme, which is based completely on the Neumann series solution of Fredholm integral equation. This scheme indicates that the essence of MCRT is the calculation of infinite terms of multiple integrals in Neumann solution simultaneously. Under this perspective we redescribed MCRT procedure systematically, in which the main work amounts to choose an associated probability distribution function (PDF) for a set of random variables and the corresponding unbiased estimation functions. We can select a relatively optimal estimation procedure that has a lower variance from an infinite possible choices, such as the term by term estimation. In this scheme, MCRT can be regarded as a pure problem of integral evaluation, rather than as the tracing of random walking photons. Keeping this in mind, one can avert some subtle intuitive mistakes. In addition the δ-functions in these integrals can be eliminated in advance by integrating them out directly. This fact together with the optimal chosen random variables can remarkably improve the Monte Carlo (MC) computational efficiency and accuracy, especially in systems with axial or spherical symmetry. An MCRT code, Lemona(Linear Integral Equations' Monte Carlo Solver Based on the Neumann solution), has been developed completely based on this scheme. Finally, we intend to verify the validation of Lemon, a suite of test problems mainly restricted to flat spacetime have been reproduced and the corresponding results are illustrated in detail. © 2021, CC BY.

关键词： Monte Carlo methods

A correction method for the telluric absorptions and application to Lijiang observatory

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arXiv 2021年

作者： Lu, Kai-Xing Zhang, Zhi-Xiang Huang, Ying-Ke Ren, An-Bing Xu, Liang Feng, Hai-Cheng Xin, Yu-Xin Ding, Xu Yu, Xiao-Guang Bai, Jin-Ming Yunnan Observatories Chinese Academy of Sciences Kunming650011 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650011 China Department of Astronomy Xiamen University Xiamen Fujian361005 China Qian Xuesen Laboratory of Space Technology China Academy of Space Technology 104 Youyi Road Haidian District Beijing100094 China Department of Astronomy China West Normal University 1 Shida Road Shunqing District Nanchong637002 China

Observing a telluric standard star for correcting the telluric absorption lines of spectrum will take a significant amount of precious telescope time, especially in the long-term spectral monitoring project. Beyond that, it’s difficult to select a suitable telluric standard star near in both time and airmass to the scientific object. In this paper, we present a method of correcting the telluric absorption lines by combining the advantages of long slit spectroscopy. By rotating the slit, we observed the scientific object and a nearby comparison star in one exposure, so that the spectra of both objects should have the same telluric transmission spectrum. The telluric transmission spectrum was constructed by dividing the observed spectrum of comparison star by its stellar template, and was used to correct the telluric absorption lines of the scientific object. Using the long slit spectrograph of Lijiang 2.4-meter telescope, we designed a long-term spectroscopic observation strategy, and finished a four-year spectroscopic monitoring for a pair of objects (an active galactic nuclei and an non-varying comparison star). We applied this method to correct the telluric absorption lines of the long-term monitored spectra by Lijiang 2.4-meter telescope, and investigated the variation of the telluric absorptions at Lijiang Observatory. We found that the telluric absorption transparency is mainly modulated by the seasonal variability of the relative humidity, airmass and seeing. Using the scatter of the [O III] λ5007 fluxes emitted from the narrow-line region of active galactic nuclei as an indicator, we found that the correction accuracy of the telluric absorption lines is 1%. © 2021, CC BY.

关键词： Stars

A spectral data release for 104 Type II Supernovae from the Tsinghua Supernova Group

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arXiv 2024年

作者： Lin, Han Wang, Xiaofeng Zhang, Jujia Xiang, Danfeng Zhang, Tianmeng Zhao, Xulin Zhang, Xinghan Sai, Hanna Rui, Liming Mo, Jun Xi, Gaobo Huang, Fang Li, Xue Cai, Yongzhi Lin, Weili Lin, Jie Wu, Chengyuan Zhang, Jicheng Chen, Zhihao Li, Zhitong Li, Wenxiong Li, Linyi Zhang, Kaicheng Miao, Cheng Chen, Juncheng Fan, Zhou Fu, Jianning Qian, Shengbang Wu, Hong Wu, Xue-Bing Yan, Jingzhi Zhang, Huawei Zhang, Junbo Zhang, Liyun Zheng, Jie Zhai, Qian Yan, Shengyu Physics Department Tsinghua University Beijing100084 China Key Laboratory of Radio Astronomy and Technology Chinese Academy of Sciences A20 Datun Road Chaoyang District Beijing100101 China Yunnan Observatories Chinese Academy of Sciences Kunming650011 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650011 China International Centre of Supernovae Yunnan Key Laboratory Kunming650216 China Institute for Frontiers in Astronomy and Astrophysics Beijing Normal University Beijing102206 China Key Laboratory of Space Astronomy and Technology National Astronomical Observatories Chinese Academy of Sciences 20A Datun Road Beijin China School of Astronomy and Space Science University of Chinese Academy of Sciences Beijing101408 China School of Science Tianjin University of Technology Tianjin300384 China School of Physics and Information Engineering Jiangsu Second Normal University Jiangsu Nanjing211200 China Department of Astronomy Shanghai Jiao Tong University Shanghai200240 China Department of Astronomy University of Science and Technology Hefei China Department of Astronomy Beijing Normal University Beijing1000875 China Key Laboratory of Optical Astronomy National Astronomical Observatories Chinese Academy of Sciences Beijing100101 China Wuzhou University China Department of Astronomy School of Physics and Astronomy Yunnan University Kunming650091 China National Astronomical Observatories Chinese Academy of Sciences Beijing100101 China Department of Astronomy School of Physics Peking University Beijing100871 China Purple Mountain Observatory Chinese Academy of Sciences Nanjing China College of Physics Guizhou University Guiyang China

We present 206 unpublished optical spectra of 104 type II supernovae obtained by the Xinglong 2.16m telescope and Lijiang 2.4m telescope during the period from 2011 to 2018, spanning the phases from about 1 to 200 days after the SN explosion. The spectral line identifications, evolution of line velocities and pseudo equivalent widths, as well as correlations between some important spectral parameters are presented. Our sample displays a large range in expansion velocities. For instance, the Fe ii 5169 velocities measured from spectra at t ∼ 50 days after the explosion vary from 2000 km s−1 to 5500 km s−1, with an average value of 3872 ± 949 km s−1. Power-law functions can be used to fit the velocity evolution, with the power-law exponent quantifying the velocity decline rate. We found an anticorrelation existing between Hβ velocity at mid-plateau phase and its velocity decay exponent, SNe II with higher velocities tending to have smaller velocity decay rate. Moreover, we noticed that the velocity decay rate inferred from the Balmer lines (i.e., Hα and Hβ) have moderate correlations with the ratio of absorption to emission for Hα (a/e). In our sample, two objects show possibly flash-ionized features at early phases. Besides, we noticed that multiple high-velocity components may exist on the blue side of hydrogen lines of SN 2013ab, possibly suggesting that these features arise from complex line forming region. All our spectra can be found in WISeREP and Zenodo. Copyright © 2024, The Authors. All rights reserved.

关键词： Supernovae

Comparing the Super-Eddington accretion of SMC X-3 and RX J0209.6-7427 with Swift J0243.6+6124

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arXiv 2022年

作者： Liu, Jiren Vasilopoulos, Georgios Ge, MingYu Ji, Long Weng, Shan-Shan Zhang, Shuang-Nan Hou, Xian Beijing Planetarium 138 Sizhimenwai Road Beijing100044 China Observatoire astronomique de Strasbourg UMR 7550 StrasbourgF-67000 France Institute of High Energy Physics Chinese Academy of Sciences Beijing100049 China School of Physics and Astronomy Sun Yat-sen University 2 Daxue Road Guangdong Zhuhai519082 China Department of Physics Institute of Theoretical Physics Nanjing Normal University Nanjing210023 China Yunnan Observatories Chinese Academy of Sciences Kunming650216 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650216 China

We study the giant outbursts of SMC X-3 and RX J0209.6-7427 to compare their super-Eddington accretion regime with that of Swift J0243.6+6124. The high double-peak profile of SMC X-3 is found to be 0.25 phase offset from that below 2.3 × 1038erg s−1, which is similar to Swift J0243 (happened around 0.9 × 1038erg s−1). The profile of RX J0209 shows a similar 0.25 phase offset between high double-peak and low double-peak around 1.25 × 1038erg s−1. The 0.25 phase offset corresponds to a 90 degree angle change of the emission beam and strongly supports for a transition from a fan beam to a pencil beam. Their critical luminosities imply a surface magnetic field ∼ 4 × 1013 G and 2 × 1013 G for SMC X-3 and RX J0209, respectively, based on the recently measured cyclotron line of Swift J0243. The spin-up rate and luminosity of SMC X-3 follows a relation of ν ∝ L0.94±0.03, while that of RX J0209 follows ν ∝ L1.00±0.03, which are similar to Swift J0243 and consistent with the prediction of a radiation-pressure-dominated (RPD) disk. These results indicate that accretion columns are indeed formed above Eddington luminosity, and the population of ULXPs likely corresponds to X-ray pulsars of highest magnetic field. Copyright © 2022, The Authors. All rights reserved.

关键词： Luminance

Detection of δ Scuti pulsators in the eclipsing binaries observed by TESS

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arXiv 2022年

作者： Chen, Xinghao Ding, Xu Cheng, Liantao Zhang, Xiaobin Li, Yan Ji, Kaifan Xiong, Jianping Li, Xuzhi Luo, Changqing Yunnan Observatories Chinese Academy of Sciences P.O. Box 110 Kunming650216 China Key Laboratory for Structure and Evolution of Celestial Objects Chinese Academy of Sciences P.O. Box 110 Kunming650216 China School of Opto-electronic Engineering Zaozhuang University Zaozhuang277160 China Key Laboratory of Optical Astronomy National Astronomical Observatories Chinese Academy of Sciences Beijing100012 China University of Chinese Academy of Sciences Beijing100049 China Center for Astronomical Mega-Science Chinese Academy of Sciences 20A Datun Road Chaoyang District Beijing100012 China Deep Space Exploration Laboratory Department of Astronomy University of Science and Technology of China Hefei230026 China School of Astronomy and Space Sciences University of Science and Technology of China Hefei230026 China

Based on 2-minute cadence TESS data from sectors 1-50, we report the results of the systematic extraction of δ Scuti-type pulsations in the 6431 eclipsing binaries with orbital periods shorter than 13 days. A total number of 242 pulsators were found in those systems, including 143 new discoveries. We examined their pulsation properties based on the H-R diagram and the relationships between the dominant pulsation period Pdom, orbital period Porb, and effective temperature Teff. As a consequence, 216 targets are likely δ Scuti stars (123 new), 11 likely γ Doradus-δ Scuti hybrid stars (8 new), 5 likely β Cephei stars (4 new), 4 likely δ Scuti-γ Doradus hybrid stars (3 new), 3 likely Maia stars (3 new), 2 likely pulsating red giants (1 new), and a new unclassified star. As for the 6 new δ Scuti pulsators in eclipsing binaries with Porb dom/Porb ratio. This may indicate that Pdom and Porb are uncorrelated for them. Finally, we statistically analyzed the dominant pulsation periods of the 216 δ Scuti stars in eclipsing binaries. Those stars concentrate around 225 µHz and the proportion of stars in the high-frequency region is significantly higher than that of single stars, which could be ascribed to the mass transfer process. Copyright © 2022, The Authors. All rights reserved.

关键词： Mass transfer