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Lijiang 2.4-meter Telescope and its instruments

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

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J115307.93+353528.2—Spectroscopic Twin Binary, Composed of Solar Like Stars. Orbital Solution from Poorly Resolved Double-line structure

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Research Notes of the AAS 2024年第7期8卷 175-175页

作者： Mikhail Yu. Kovalev Xuefei Chen Zhanwen Han Yunnan Observatories China Academy of Sciences Kunming 650216 People’s Republic of China mikhail.kovalev@*** Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming 650011 People’s Republic of China Center for Astronomical Mega-Science Chinese Academy of Sciences 20A Datun Road Chaoyang District Beijing 100012 People’s Republic of China

We present a study of double-lined spectroscopic binary (SB2) J115307.93+353528.2 based on data from the Large Sky Area Multi-Object fiber Spectroscopic Telescope (LAMOST) medium resolution survey (MRS). We use full-spectrum fitting to derive radial velocities and spectral parameters, which suggest that this is a "twin" system of two nearly identical stars, which are similar to the Sun. The orbital solution tells us that it is relatively wide pair of stars on slightly eccentric orbit with period P ≃ 206 days. This result shows that LAMOST-MRS data can be used to detect such twin binaries even when double-line structure is poorly resolved in the spectra. Changes of $(V\sin i)$ $(V \sin i)$ values from single star model analysis allows us to reliably select su

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

arXiv

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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

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Distinguishing super-Nyquist frequencies via their temporal variation in γ Doradus stars from continuous photometry

arXiv

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arXiv 2024年

作者： Wang, Xuan Zong, Weikai Ma, Xiao-Yu Charpinet, Stéphane Wu, Tao Wang, Haotian Institute for Frontiers in Astronomy and Astrophysics Beijing Normal University Beijing102206 China School of Physics and Astronomy Beijing Normal University Beijing100875 China International Centre of Supernovae Yunnan Key Laboratory Kunming650216 China Institute Université de Liège Allée du 6 Août 19C Liège4000 Belgium IRAP CNRS UPS CNES Université de Toulouse 14 av. Edouard Belin Toulouse31400 France 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 Institute of Astronomy KU Leuven Celestijnenlaan 200D Leuven3001 Belgium

As mixed with real pulsations, the reflection of super-Nyquist frequencies (SNFs) pose a threat to asteroseismic properties. Although SNFs have been studied in several pulsating stars, a systematic survey remains scarcely explored. Here we propose a method to identify SNFs from Kepler and TESS photometry by characterizing their periodic frequency modulations using a sliding Fourier transform. After analyzing long cadence photometry in the Kepler legacy, we have identified 304 SNFs in 56 stars from 45607 frequencies in ∼ 600 γ Doradus stars, corresponding to a fraction of approximately 0.67% and 9.2%, respectively. Most SNFs are detected in the frequency range of pressure mode over 120 µHz and the fraction of SNF detection increases as frequency up to ∼ 7%. We barely found two potential SNFs mixed with gravity modes in two γ Doradus stars. These findings indicate that SNFs have a negligible impact on the global seismic properties, such as those derived from period spacing in γ Doradus stars. However, we stress that SNFs must be carefully and systematically examined by this method in other pulsating stars, particularly δ Scuti and hot B subdwarf stars, to establish a solid foundation for precise asteroseismolgy of various types of pulsators. Copyright © 2024, The Authors. All rights reserved.

关键词： Photometry

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Minute-cadence Observations of the LAMOST Fields with the TMTS: III. Statistic Study of the Flare Stars from the First Two Years

arXiv

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arXiv 2023年

作者： Liu, Qichun Lin, Jie Wang, Xiaofeng Gu, Shenghong Shi, Jianrong Zhang, Liyun Xi, Gaobo Mo, Jun Cai, Yongzhi Chen, Liyang Chen, Zhihao Guo, Fangzhou Jiang, Xiaojun Li, Gaici Li, Wenxiong Lin, Han Lin, Weili Liu, Jialian Miao, Cheng Ma, Xiaoran Peng, Haowei Xiang, Danfeng Yan, Shengyu Zhang, Jicheng Zhang, Xinhan Physics Department Tsinghua Center for Astrophysics Tsinghua University Beijing100084 China Beijing Planetarium Beijing Academy of Science and Technology Beijing100044 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 CAS Key Laboratory of Optical Astronomy National Astronomical Observatories Chinese Academy of Sciences Beijing100101 China School of Astronomy and Space Science University of Chinese Academy of Sciences Beijing100049 China College of Physics College of Big Data and Information Engineering Guizhou University Guiyang550025 China Center for Astronomical Mega-Science Chinese Academy of Sciences 20A Datun Road Chaoyang District Beijing100012 China The School of Physics and Astronomy Tel Aviv University Tel Aviv69978 Israel Department of Astronomy Beijing Normal University Beijing100875 China

Tsinghua University-Ma Huateng Telescopes for Survey (TMTS) aims to detect fast-evolving transients in the Universe, which has led to the discovery of thousands of short-period variables and eclipsing binaries since 2020. In this paper, we present the observed properties of 125 flare stars identified by TMTS within the first two years, with an attempt to constrain their eruption physics. As expected, most of these flares were recorded in late-type red stars with GBP − GRP > 2.0 mag;however, the flares associated with bluer stars tend to be on average more energetic and have broader profiles. The peak flux (Fpeak) of the flare is found to depend strongly on the equivalent duration (ED) of the energy release, i.e., Fpeak ∝ ED0.72±0.04, which is consistent with results derived from the Kepler and Evryscope samples. This relation is likely related to the magnetic loop emission, while, for the more popular non-thermal electron heating model, a specific time evolution may be required to generate this relation. We notice that flares produced by hotter stars have a flatter Fpeak ∝ ED relation compared to that from cooler stars. This is related to the statistical discrepancy in light-curve shape of flare events with different colors. In spectra from LAMOST, we find that flare stars have apparently stronger Hα emission than inactive stars, especially at the low temperature end, suggesting that chromospheric activity plays an important role in producing flares. On the other hand, the subclass with frequent flares is found to show Hα emission of similar strength in its spectra to that recorded with only a single flare but similar effective temperature, implying that the chromospheric activity may not be the only trigger for eruptions. Copyright © 2023, The Authors. All rights reserved.

关键词： Stars

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Generalized split monopole magnetospheres: The effects of current sheets

arXiv

引用

arXiv 2020年

作者： Li, Huiquan Wang, Jiancheng Yunnan Observatories Chinese Academy of Sciences Kunming650216 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650216 China Center for Astronomical Mega-Science Chinese Academy of Sciences Beijing100012 China

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

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

arXiv

引用

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

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Probing the Shock Breakout Signal of SN 2024ggi from the Transformation of Early Flash Spectroscopy

arXiv

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arXiv 2024年

作者： Zhang, Jujia Dessart, Luc Wang, Xiaofeng Zhai, Qian Yang, Yi Li, Liping Lin, Han Valerin, Giorgio Cai, Yongzhi Guo, Zhen Wang, Lingzhi Zhao, Zeyi Wang, Zhenyu Yan, Shengyu Kunming650216 China International Centre of Supernovae Yunnan Key Laboratory Kunming650216 China Key Laboratory for the Structure and Evolution of Celestial Objects CAS Kunming650216 China Institut d’Astrophysique de Paris CNRS-Sorbonne Université 98 bis boulevard Arago ParisF-75014 France Physics Department Tsinghua University Beijing100084 China Department of Astronomy University of California BerkeleyCA94720-3411 United States INAF-Osservatorio Astronomico di Padova Vicolo dell’Osservatorio 5 Padova35122 Italy Instituto de Física y Astronomía Universidad de Valparaíso ave. Gran Bretaña 1111 Casilla 5030 Valparaíso Chile Centre for Astrophysics Research University of Hertfordshire HatfieldAL10 9AB United Kingdom Millennium Institute of Astrophysics Nuncio Monseñor Sotero Sanz 100 Of. 104 Providencia Santiago Chile National Astronomical Observatories CAS Beijing China

We present early-time, hour-to-day cadence spectroscopy of the nearby type II supernova (SN II) 2024ggi, which was discovered at a phase when the SN shock just emerged from the red-supergiant (RSG) progenitor star. Over the first few days after the first light, SN 2024ggi exhibited prominent narrow emission lines formed through intense and persistent photoionization of the nearby circumstellar material (CSM). In the first 63 hours, spectral lines of He, C, N, and O revealed a rapid rise in ionization, as a result of the progressive sweeping-up of the CSM by the shock. The duration of the IIn-like spectra indicates a dense and relatively confined CSM distribution extending up to ∼ 4 × 1014 cm. Spectral modeling reveals a CSM mass loss rate at this region exceeding 5× 10−3 M☉ yr−1 is required to reproduce low-ionization emissions, which dramatically exceeds that of an RSG. Analyzing Hα emission shift implies the velocity of the unshocked outer CSM to be between 20 and 40 km s−1, matching the typical wind velocity of an RSG. The differences between the inner and outer layers of the CSM and an RSG progenitor highlight a complex mass loss history before the explosion of SN 2024ggi. © 2024, CC BY.

关键词： Supernovae

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A characteristic optical variability time scale in jetted active galactic nuclei: a large gamma-ray emission sample

arXiv

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arXiv 2025年

作者： Xiong, Dingrong Sun, Mouyuan Wang, Jun-Xian Fan, Junhui Xue, Yongquan Gu, Minfeng Chen, Liang Chen, Yongyun Ding, Nan Guo, Fei Mao, Jirong Ren, Guowei Xue, Rui Yan, Dahai Yang, Shenbang Zhang, Haiyun Bai, Jinming Yunnan Observatories 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 Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences 396 Yangfangwang Guandu District Kunming650216 China Department of Astronomy Xiamen University Fujian Xiamen361005 China Department of Astronomy University of Science and Technology of China Hefei230026 China School of Astronomy and Space Science University of Science and Technology of China Hefei230026 China Center for Astrophysics Guangzhou University Guangzhou510006 China Astronomy Science and Technology Research Laboratory Department of Education of Guangdong Province Guangzhou510006 China Key Laboratory for Research in Galaxies and Cosmology Shanghai Astronomical Observatory Chinese Academy of Sciences 80 Nandan Road Shanghai200030 China College of Physics and Electronic Engineering Qujing Normal University Qujing655011 China School of Physical Science and Technology Kunming University 650214 China Yunnan Normal University Kunming650500 China Department of Physics Zhejiang Normal University Jinhua321004 China Department of Astronomy Key Laboratory of Astroparticle Physics of Yunnan Province Yunnan University Kunming650091 China Faculty of Science Kunming University of Science and Technology Kunming650500 China

The variability mechanisms from jetted AGNs are still under debate. Here the damped random walk (DRW) model, implemented through Gaussian Processe (GPs), is used to fit the ZTF long-term optical light curves of 1684 γ-ray emission jetted AGNs. This analysis yields one of the largest samples with characteristic optical variability timescales for jetted AGNs. A single DRW model from GPs can fit the optical light curve of most jetted AGNs well/potentially well, while there are still some jetted AGNs whose light curve can not be fitted well by a single DRW model. After the jet power, proxied by gamma-ray luminosity, is introduced as a new parameter, new relationships among intrinsic variability time scales, black hole mass and jet power are discovered for efficient accretion AGNs (formula presented) with scatter of approximately 0.09 dex) and for inefficient accretion AGNs (formula presented) with scatter of approximately 0.14 dex), respectively. Our results support that the optical variability of jetted AGNs with efficient accretion may originate within the standard accretion disk at UV emitting radii similar to non-jetted AGNs, and is directly related to the acceleration of shock in the jet and then enhanced through the beaming effect in beamed AGNs. For the jetted AGNs with inefficient accretion, the intrinsic timescale is consistent with the escape timescale of electrons. © 2025, CC BY.

关键词： Active Galactic Nuclei

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A systematic study of the high-frequency bump in the black-hole low-mass X-ray binary GX 339−4

arXiv

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arXiv 2023年

作者： Zhang, Yuexin Méndez, Mariano Motta, Sara E. Zdziarski, Andrzej A. Marcel, Grégoire García, Federico Altamirano, Diego Belloni, Tomaso M. Zhang, Liang Timmermans, Thimo Zhang, Guobao Kapteyn Astronomical Institute University of Groningen P.O. BOX 800 Groningen9700 AV Netherlands Center for Astrophysics Harvard & Smithsonian 60 Garden St CambridgeMA02138 United States MerateI-23807 Italy Nicolaus Copernicus Astronomical Center Polish Academy of Sciences Bartycka 18 WarszawaPL-00-716 Poland Institute of Astronomy University of Cambridge Madingley Road CambridgeCB3 0HA United Kingdom Villa Elisa Buenos Aires1894 Argentina School of Physics and Astronomy University of Southampton SouthamptonSO17 1BJ United Kingdom Key Laboratory of Particle Astrophysics Institute of High Energy Physics Chinese Academy of Sciences Beijing100049 China Yunnan Observatories Chinese Academy of Sciences Kunming650216 China Key Laboratory for the Structure and Evolution of Celestial Objects CAS Kunming650216 China

The high-frequency bump, characterized by a frequency exceeding ∼30 Hz, represents a seldom-explored time-variability feature in the power density spectrum (PDS) of black-hole X-ray binaries. In the 2002, 2004, 2007 and 2010 outbursts of GX 339−4, the bump has been occasionally observed in conjunction with type-C quasi-periodic oscillations (QPOs). We systematically study the properties of the bump during these four outbursts observed by Rossi X-ray Timing Explorer (RXTE) in the 2-60 keV bands and detect the bump in 39 observations. While the frequencies of the type-C QPOs are in the range of ∼0.1-9 Hz, the root-mean-square (rms) amplitude of the bump shows an evolution in the hardness ratio versus the type-C QPO frequency plot. By comparing the rms amplitude of the bump with the corona temperature and simultaneous radio jet flux of the source, as previously studied in GRS 1915+105, we establish that in the hard state of GX 339−4, the bump is always strong, with the measurements of the rms amplitude in the range of 4-10%. At the same time, the corona temperature is high and the radio flux is low. These findings indicate that, using the bump as a proxy, the majority of the accretion energy is directed towards the hot corona rather than being channeled into the radio jet. We discuss this phenomenon in terms of an inefficient energy transfer mechanism between the corona and jet in GX 339−4. © 2023, CC BY.

关键词： Black holes

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