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arXiv 2024年

作者： Zhang, F. Li, L. Han, Z. Wang, X. 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 University of Chinese Academy of Sciences Beijing100049 China International Centre of Supernovae Yunnan Key Laboratory Kunming650216 China

We need to resolve the individual stars for binary fraction determinations of stellar systems. Therefore, it is not possible to obtain the binary fractions for dense or distant stellar systems. We proposed a method to determine the binary fraction of a dense or distant stellar system. The method is to first determine the binary fraction variation for any two adjacent regions and then add up those binary fraction variations along the radial direction to obtain the binary fraction for a stellar system. Binary fraction variation is derived by using ten binary fraction-sensitive spectral absorption feature indices (SAFIs) and the binary fraction variation calibrations in terms of these SAFIs. Using this method, we first presented the binary fraction variations for twenty-one Galactic globular clusters (GCs). By comparisons, we find that they agree well with the binary fractions based on the main-sequence fiducial line method by previous studies. This verifies that the above mentioned method is feasible. Next, we presented the binary fraction variations of thirteen Galactic GCs. We gave the relationships between binary fraction and various parameters, and found that binary fraction is negatively correlated with NHB and NRR, binary fraction of some studies is not strongly correlated with NBS, and the number of GCs with large binary fraction is greater at extreme blue horizontal branch population ratio. At last, if we want to obtain more accurate binary fraction, we suggest that the spectroscopic and photometric observations are conducted at an appropriate area interval for a stellar system. © 2024, CC BY-NC-ND.

关键词： Stars

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A robust model for the origin of optical quasi-periodic variability in supersoft X-ray sources

arXiv

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arXiv 2022年

作者： Zhao, Weitao Meng, Xiangcun Cui, Yingzheng Liu, Zheng-Wei Yunnan Observatories Chinese Academy of Sciences 650216 China University of Chinese Academy of Sciences Beijing100049 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650216 China

Context. Supersoft X-ray sources (SSSs) are known as possible progenitors of Type Ia supernovae. The quasi-periodic variability has been detected in the optical light curves of SSSs. However, the exact origin of such quasi-periodic observable features remains a mystery. Aims. In this paper, we aim to reproduce the observed optical quasi-periodic variability of SSSs by proposing a white dwarf (WD) accretion model with a periodic mass transfer caused by the irradiation of supersoft X-ray onto the companion star. Methods. Assuming that a periodic mass transfer from the companion star to the WD can be caused while the supersoft X-ray irradiates the companion star, we used MESA to simulate the WD accretion process and the subsequent WD evolution by adopting a periodic jagged accretion rate. Results. Comparing our results to the optical light curves of a well-observed SSS RX J0513.9-6951, we find that our models can reproduce the quasi-periodic transition between the optical high and low states of RX J0513.9-6951 because the periodic accretion rate can lead to the WD photosphere expands and contracts periodically in our models. In addition, we find that the transitional periods of the SSSs in our models strongly depend on the mass of the accreting WDs. The more massive the WD mass is, the shorter the transitional period. Conclusions. Based on our results, we suggest that the periodic mass transfer caused by the irradiation of supersoft X-ray onto the companion star may be the origin of the observed optical quasi-periodic variability in SSSs. In addition, our results indicate that the observed optical transition period of a SSS may be useful for the rough estimate of the mass of an accreting WD. © 2022, CC0.

关键词： White dwarfs

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The eccentricity enhancement effect of intermediate-mass-ratio-inspirals: dark matter and black hole mass

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Chinese Physics C 2021年第1期45卷 414-426页

作者： Meirong Tang Zhaoyi Xu Jiancheng Wang Yunnan Observatories Chinese Academy of SciencesKunming 650216China College of Physics Guizhou UniversityGuiyang550025China Key Laboratory of Particle Astrophysics Institute of High Energy PhysicsChinese Academy of SciencesBeijing 100049China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of SciencesKunming 650216China Center for Astronomical Mega-Science Chinese Academy of SciencesBeijing 100012China University of Chinese Academy of Sciences Beijing 100049China

It was found that dark matter(DM) in an intermediate-mass-ratio-inspiral(IMRI) system has a significant enhancement effect on the orbital eccentricity of a stellar massive compact object, such as a black hole(BH),which may be tested by space-based gravitational wave(GW) detectors, including LISA, Taiji, and Tianqin in future observations. In this paper, we study the enhancement effect of the eccentricity for an IMRI under different DM density profiles and center BH masses. Our results are as follows:(1) in terms of the general DM spike distribution,the enhancement of the eccentricity is basically consistent with the power-law profile, which indicates that it is reasonable to adopt the power-law profile;(2) in the presence of a DM spike, the different masses of the center BH will affect the eccentricity, which provides a new way for us to detect the BH’s mass;and(3) considering the change in the eccentricity in the presence and absence of a DM spike, we find that it is possible to distinguish DM models by measuring the eccentricity at a scale of approximately 105 GM/c2.

关键词： BH DM models IMRI DM spike eccentricity

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Prospects of the multi-channel photometric survey telescope in the cosmological application of Type Ia supernovae

arXiv

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arXiv 2024年

作者： Wang, Zhenyu Zhang, Jujia Er, Xinzhong Bai, Jinming Yunnan Observatories Chinese Academy of Sciences Kunming650216 China University of Chinese Academy of Sciences Beijing100049 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650216 China International Centre of Supernovae Yunnan Key Laboratory Kunming50216 China South-Western Institute for Astronomy Research Yunnan University Kunming650500 China

The Multi-channel Photometric Survey Telescope (Mephisto) is a real-time, threecolor photometric system designed to capture the color evolution of stars and transients accurately. This telescope system can be crucial in cosmological distance measurements of low-redshift (low-z, z 0.1) Type Ia supernovae (SNe Ia). To optimize the capabilities of this instrument, we perform a comprehensive simulation study before its official operation is scheduled to start. By considering the impact of atmospheric extinction, weather conditions, and the lunar phase at the observing site involving the instrumental features, we simulate the light curves of SNe Ia obtained by the Mephisto. The best strategy in the case of SN Ia cosmology is to take the image at an exposure time of 130 s with a cadence of 3 days. In this condition, Mephisto can obtain hundreds of high-quality SNe Ia to achieve a distance measurement better than 4.5%. Given the on-time spectral classification and monitoring of the Lijiang 2.4 m Telescope at the same observatory, Mephisto, in the whole operation, can significantly enrich the well-calibrated sample of supernovae at low-z and improve the calibration accuracy of high-z SNe Ia. © 2024, CC BY.

关键词： Supernovae

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Simulating the Escaping Atmosphere of GJ436 b with two-fluid Magnetohydrodynamic Models-

arXiv

引用

arXiv 2024年

作者： Xing, Lei Guo, Jianheng Yan, Dongdong Yang, Chuyuan Yunnan Observatories Chinese Academy of Sciences P.0.Box110 Kunming650216 China Yuquan Road Shijingshan District Beijing100049 China Key Laboratory for Structure and Evolution of Celestial Objects Chinese Academy of Sciences P.0.Box110 Kunming650216 China International Centre of Supernovae Yunnan Key Laboratory Kunming650216 China

Observations of transmission spectra reveals that hot Jupiters and Neptunes are likely to possess escaping atmospheres driven by stellar radiation. Numerous models predict that magnetic fields may exert significant influences on the atmospheres of hot planets. Generally, the escaping atmospheres are not entirely ionized, and magnetic fields only directly affect the escape of ionized components within them. Considering the chemical reactions between ionized components and neutral atoms, as well as collision processes, magnetic fields indirectly impact the escape of neutral atoms, thereby influencing the detection signals of planetary atmospheres in transmission *** order to simulate this process, we developed a magneto-hydrodynamic multi-fluid model based on MHD code PLUTO. As an initial exploration, we investigated the impact of magnetic fields on the decoupling of H+ and H in the escaping atmosphere of the hot Neptune GJ436 b. Due to the strong resonant interactions between H and H+. The coupling between them is tight even if the magnetic field is strong. However, our simulation results indicate that under the influence of magnetic fields, there are noticeable regional differences in the decoupling of H+ and H. With the increase in magnetic field strength, the degree of decoupling also increases. For heavier particles such as O, the decoupling between O and H+ is more pronounced. our findings provide important insights for future studies on the decoupling processes of heavy atoms in the escaping atmospheres of hot Jupiters and hot Neptunes under the influence of magnetic fields. © 2024, CC BY-NC-ND.

关键词： Magnetohydrodynamics

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A method of photometric data extraction for asteroids from time-domain surveys

arXiv

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arXiv 2024年

作者： Xu, Xiaoyun Wang, Xiaobing Muinonen, Karri Penttilä, Antti Luo, Nanping Gu, Shenghong Sun, Leilei Xu, Fukun Liu, Yisi Xiang, Yue Cao, Dongtao Wang, Jianhua Yunnan Observatories Chinese Academy of Sciences Kunming650216 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650216 China University of Chinese Academy of Sciences Beijing100049 China Department of Physics University of Helsinki P.O. box 64 FI-00014 Finland Deep Space Exploration Laboratory Beijing100043 China

The lightcurves of asteroids are essential for determining their physical characteristics, including shape, spin, size, and surface composition. However, most asteroids are missing some of these basic physical parameters due to lack of photometric data. Although a few telescopes or surveys are specially designed for photometric lightcurve observations of asteroids, many ground-based and space-based sky surveys for hunting new exoplanets, transient events, etc., should capture numerous small Solar System objects. This will benefit the physical studies of these objects. In order to extract data of these moving objects from time-domain photometric surveys, we have developed a new method using the model tree algorithm in the field of machine learning. A dedicated module is built to automatically identify moving objects in dataset, and extract their photometric and astrometric data. As the first application of this novel method, we have analyzed data in five fields of the Yunnan-Hong Kong wide field photometric (YNHK) survey, from which 538 lightcurves of 211 asteroids are successfully extracted. Meanwhile, we also tested the method based on the data from NASA’s Transiting Exoplanet Survey Satellite, and the result proves the reliability of our method. With derived lightcurves of 13 asteroids from the YNHK survey, we have determined their synodic spin periods, among which the periods of 4 asteroids are estimated for the first time. In future, we are going to apply this method to search for small objects in the outer part of the Solar System from the Chinese Space Station Telescope survey. Copyright © 2024, The Authors. All rights reserved.

关键词： NASA

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The polarization-angle flip in GRB prompt emission

arXiv

引用

arXiv 2024年

作者： Cheng, Kangfa Zhao, Xiaohong Mao, Jirong Chen, Zhifu School of Mathematics and Physics Guangxi Minzu University Nanning530006 China Yunnan Observatories Chinese Academy of Sciences Kunming650011 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Science China Center for Astronomical Mega-Science Chinese Academy of Science 20A Datun Road Chaoyang District Beijing100012 China

Context. In recent years, some polarization measurements of gamma-ray bursts (GRBs) have been reported, and the polarization-angle (PA) rotation in the prompt emission phase has been found in several bursts. The physical mechanism of the PA evolution is still unclear. In this work, we studied the origin of the PA rotation in a toroidal magnetic field. Aims. We aim to provide an explanation for the PA rotation in GRBs and find the physical conditions that lead to the rotation by 90 degrees in the toroidal magnetic-field (MF) model. Moreover, we present some observable polarization properties in the MF model that can be tested in the future. Methods. We calculated the instantaneous polarization degree (PD) from a top-hat jet with different normalized viewing angles (q = θv/θj), jet opening angles (θj), and jet Lorentz factors (Γ) in three wavebands. When the PD changes between positive and negative values, it means that the PA flips by 90 degrees. On these grounds, we can summarize the range of parameters required for these PA flips. Considering these parameter conditions, we can further estimate the observed rate of the GRBs exhibiting such PA rotations. Results. We find that the PA rotation in the toroidal MF is primarily related to three critical factors: the viewing angle, the jet opening angle, and the jet Lorentz factor. Additionally, the PA can experience flips of 90 degrees twice. The conditions for the flips are q 0.5 (except for q 1) and yj = (Γθj)2 4. However, the two flips in the PA might not be concurrently observable due to the constraint of flux. Taking these conditions into account and assuming a random orientation between the jet axis and the line of sight (LOS), we obtain a theoretical upper limit (without any constraints) for the observed rate of GRBs in the X-ray or γ-ray band displaying the flips in PA as Rch 80%. We further constrain the observed rate as Rch ∼ 16% according to the maximal post-flip polarized flux level, where the observed rate of

关键词： Polarization

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Constraining evolution of magnetic field strength in the dissipation region of two BL Lac objects

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Research in Astronomy and Astrophysics 2021年第12期21卷 351-356页

作者： Xu-Liang Fan Da-Hai Yan Qing-Wen Wu Xu Chen School of Mathematics Physics and StatisticsShanghai University of Engineering ScienceShanghai 201620China Yunnan Observatories Chinese Academy of SciencesKunming 650011China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of SciencesKunming 650011China School of Physics Huazhong University of Science and TechnologyWuhan 430074China Shandong Provincial Key Laboratory of Optical Astronomy and Solar-Terrestrial Environment Institute of Space SciencesShandong UniversityWeihai 264209China

With the assumption that the optical variability timescale is dominated by the cooling time of the synchrotron process for BL Lac objects,we estimate time dependent magnetic field strength of the emission region for two BL Lac *** average magnetic field strengths are consistent with those estimated from core shift measurement and spectral energy distribution *** of magnetic field strength in the dissipation region is *** of flux and magnetic field strength shows no clear correlation,which indicates the variation of magnetic field is not the dominant reason of the variability *** evolution of magnetic field strength can provide another approach to constrain the energy dissipation mechanism in jets.

关键词： BL Lacertae objects:general BL Lacertae objects:individual(S50716+714 BL Lacertae) galaxies:magnetic fields

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Measuring clock jumps using pulsar timing

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Science China(Physics,Mechanics & Astronomy) 2020年第1期63卷 112-117页

作者： ZhiXuan Li KeJia Lee Ricardo Nicolaos Caballero YongHua Xu LongFei Hao Min Wang JianCheng Wang Yunnan Observatories Chinese Academy of SciencesKunming 650216China Kavli Institute for Astronomy and Astrophysics Peking UniversityBeijing 100871China University of Chinese Academy of Sciences Beijing 100049China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of SciencesKunming 650216China

In this paper,we investigate the statistical signal-processing algorithm to measure the instant local clock jump from the timing data of multiple *** algorithm is based on the framework of Bayesian *** order to make the Bayesian algorithm applicable with limited computational resources,we dedicated our efforts to the analytic marginalization of irrelevant *** found that the widely used parameter for pulsar timing systematics,the"Efac"parameter,can be analytically *** reduces the Gaussian likelihood to a function very similar to the Student’s *** iterative method to solve the maximum likelihood estimator is also explained in the *** pulsar timing data from the Yunnan Kunming 40-m radio telescope,we demonstrate the application of the method,where 80-ns level precision for the clock jump can be *** a precision is comparable to that of current commercial time transferring service using *** expect that the current method could help developing the autonomous pulsar time scale.

关键词： pulsars time series analysis clocks and frequency standards

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Orbital Parameters of 665 Double-lined Spectroscopic Binaries in the LAMOST Medium-Resolution Survey

arXiv

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arXiv 2025年

作者： Guo, Sufen Kovalev, Mikhail Li, Jiao Lü, Guoliang Jia, Shi Li, Zhenwei Li, Jiangdan Xiong, Jianping Yang, Mingkuan He, Tongyu Chen, Xuefei Han, Zhanwen School of Physical Science and Technology Xinjiang University Urumqi830046 China Kunming650216 China Key Laboratory for the Structure and Evolution of Celestial Objects CAS Kunming650216 China International Centre of Supernovae Yunnan Key Laboratory Kunming650216 China Key Laboratory of Optical Astronomy National Astronomical Observatories Chinese Academy of Sciences Beijing100101 China College of Physics Science and Technology Hebei University Baoding071002 China

The period, mass ratio, eccentricity, and other orbital parameters are fundamental for investigating binary star evolution. However, the number of binaries with known orbital parameters remains limited. Utilizing the LAMOST-MRS survey, we derived orbital solutions for 665 SB2 binaries by fitting the radial velocities of 1119 SB2 systems with at least six observations, employing a modified version of The Joker optimized for SB2 binaries. To ensure the reliability of the results, four selection criteria were applied: reduced chi-square, normalized mean absolute error, maximum phase gap, and RV distribution metric. After applying these criteria, 665 reliable orbits were retained. Comparison with Kepler, TESS, and ZTF light curve data shows excellent agreement, with discrepancies in some cases attributed to shorter pulsation periods observed in light curves. Additionally, good consistency is found between our periods and those of SB1 systems in Gaia data. These orbital solutions contribute to understanding binary star evolution and the statistical properties of binary populations. © 2025, CC BY-NC-SA.

关键词： Hydrographic surveys

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