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arXiv 2020年

作者： Webbink, Ronald F. Han, Zhanwen Ge, Hongwei 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 University of Chinese Academy of Sciences Beijing100049 China University of Illinois at Urbana-Champaign 1002 W Green St Urbana61801 United States

Binary evolution is indispensable in stellar evolution to understand the formation and evolution of most peculiar and energetic objects, such as binary compact objects, Type Ia supernovae, X-ray binaries, cataclysmic variables, blue stragglers, hot subdwarfs, and central binaries in planetary nebulae. Mass transfer in binary stars can change the evolutionary path and fate of the corresponding objects relative to what is expected from single stellar evolution. What is the critical mass ratio at which unstable mass transfer occurs is an unsolved fundamental problem in binary evolution. To resolve this issue, we construct the thermal equilibrium mass loss model and derive critical mass ratios for both thermal timescale mass transfer and unstable mass transfer, the latter of which occurs when the outer Lagrangian point, L2, is overfilled. Using several 3.2 M stellar models as examples, we study the stellar response to thermal equilibrium mass loss and present the thresholds for thermal timescale mass transfer. We study the possible mass transfer channels of binary systems containing a 3.2 M donor star, taking into account thermal timescale mass transfer, unstable mass transfer through L2, and dynamical timescale mass transfer. We repeat this simulation for a grid of donor stars with different masses (from 0.1 to 100 M with Z = 0.02) and at different evolutionary stages, and present our results. The results show that unstable mass transfer due to the overfilling of the outer Lagrangian point may also play an essential role in the formation of common envelopes for late red giant branch and asymptotic giant branch donors. Copyright © 2020, The Authors. All rights reserved.

关键词： Mass transfer

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Investigations into the thermal non-equilibrium of W UMa-type contact binaries

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Research in Astronomy and Astrophysics 2018年第5期18卷 83-92页

作者： Xiao Xiong Liang Liu Sheng-Bang Qian Yunnan Observatories Chinese Academy of Sciences Kunming 650011 China Key Laboratory of 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

Traditionally, some physical details（e.g., magnetic braking, energy transfer, angular momentum loss, etc.） have to be taken into consideration during investigations into the evolution of contact binaries. However, the real evolutionary processes which usually contain several of these physical mechanisms are very complicated as a result of strong interaction between components. To avoid dealing with these factors, a linear relationship is applied to the temperatures of components. It is found that the higher the mass ratio（M2/M1） of a contact system, the weaker the deviation from thermal *** this basis, a variation trend of fill-out factor（f） changing with mass ratio can be inferred, which is consistent with observations. Moreover, if we stick to this point of view, it should be natural that the number of semi-detached binaries in the predicted broken-contact phase of relaxation oscillations is less than the number in the contact phase.

关键词： stars binaries close - stars binaries eclipsing - stars evolution

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Multi-color light curves and orbital period research of eclipsing binary V1073 Cyg

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Research in Astronomy and Astrophysics 2018年第2期18卷 83-92页

作者： Xiao-Man Tian Li-Ying Zhu Sheng-Bang Qian Lin-Jia Li Lin-Qiao Jiang Yunnan Observatories Chinese Academy of Sciences Kunming 650216 China Key Laboratory of the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming 650216 China University of Chinese Academy of Sciences Beijing 100049 China School of Physics and Electronic Engineering Sichuan University of Science & Engineering Zigong 643000 China

New multi-color BVRcIc photometric observations are presented for the W UMa type eclips- ing binary V1073 Cyg. The multi-color light curve analysis with the Wilson-Devinney procedure yielded the absolute parameters of this system, showing that V 1073 Cyg is a shallow contact binary system with a fill-out factor f = 0.124（±0.011）. We collected all available times of light minima spanning 119yr, including CCD data to construct the O - C curve, and performed detailed O - C analysis. The O - C diagram shows that the period change is complex. A long-term continuous decrease and a cyclic vari- ation exist. The period is decreasing at a rate ofP = -1.04（±0.18） × 10-10 d cycle-land, with the period decrease, V1073 Cyg will evolve to the deep contact stage. The cyclic variation with a period of P3 = 82.7（±3.6） yr and an amplitude of A = 0.028（±0.002） d may be explained by magnetic activ- ity of one or both components or the light travel time effect caused by a distant third companion with M3（i1 = 90°） = 0.511 M⊙.

关键词： stars： binaries： close -- stars： binaries： eclipse -- stars： binaries： individual （V1073 Cyg）

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Lithium evolution of giant stars observed by LAMOST and Kepler

arXiv

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arXiv 2021年

作者： Zhang, Jinghua Shi, Jian-Rong Yan, Hong-Liang Li, Yaguang Gao, Qi Li, Chun-Qian Zhang, Xianfei Liu, Shuai Bi, Shaolan Zhao, Gang Li, Yan 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 Beijing100101 China School of Physics University of Sydney NSW2006 Australia Stellar Astrophysics Centre Department of Physics and Astronomy Aarhus University Ny Munkegade 120 Aarhus CDK-8000 Denmark Department of Astronomy Beijing Normal University Beijing100875 China Yunnan Observatories Chinese Academy of Sciences Kunming650216 China Key Laboratory for Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650216 China Center for Astronomical Mega-Science Chinese Academy of Sciences Beijing100012 China

Mapping lithium evolution for evolved stars will provide restrictions and constraints on the fundamental stellar interior physical processes, which further shed light on our understanding of the theory of stellar structure and evolution. Based on a sample of 1,848 giants with known evolutionary phases and lithium abundances from the LAMOST-kepler and LAMOST-K2 fields, we construct mass-radius diagrams to characterize the evolutionary features of lithium. The stars at red giant branch (RGB) phase show natural depletion along with their stellar evolution, particularly, there is no obvious crowd stars with anomalously high Li abundances near the bump. Most of the low-mass stars reaching their zero-age sequence of core-helium-burning (ZAHeB) have Li abundances around ∼1.0 dex, which show an increase of Li abundance by ∼0.6 dex compared to the stars above the bump of RGB. This suggests the helium flash can be responsible for moderate Li production. While for super Li-rich stars, some special mechanisms should be considered during helium flash. Other scenarios, such as merger, could also be interpretations given the Li-rich stars can be found at anytime during the steady state phase of core He-burning. During the core He-burning (HeB) phase, there is no indication of obvious lithium depletion. © 2021, CC BY.

关键词： Lithium

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A photmetric study of the high-mass-ratio contact binary av puppis

arXiv

引用

arXiv 2019年

作者： Han, Quan-Wang Li, Li-Fang Jiang, Deng-Kai Yunnan Observatories Chinese Academy of Sciences Kunming650216 China Key Laboratory of the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650216 China University of the Chinese Academy of Sciences Beijing100049 China

The multi-color photometric light curves for a contact binary AV Puppis (AV Pup) in V RcIcbandpasses are presented, and they are analyzed by using of the 2013 version of theWilson-Devinney (W-D) code. The solutions suggest that AV Pup is a peculiar A-subtype W UMa contact binary with a high mass ratio (q = m2/m1= 0.896) and a fill-out factor (f = 10%). Combining with our newly determined times of minimum with those collected from literatures, the orbital period changes of this system are investigated. The O - C analysis shows that the orbital period of AV Pup is increasing at a rate of dP/dt = 4.83× 10-7days yr-1, which can be explained by mass transfer from the less massive component to the more massive one. Copyright © 2019, The Authors. All rights reserved.

关键词： Photometry

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

arXiv

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arXiv 2020年

作者： Tang, Meirong Wang, Jiancheng 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

It was found that the dark matter (DM) in the intermediate-mass-ratio-inspiral (IMRI) system has a significant enhancement effect on the orbital eccentricity of the 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 (Yue & Cao 2019). In this paper, we will 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 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;(3) considering the change of the eccentricity in the presence and absence of DM spike, we find that it is possible to distinguish DM models by measuring the eccentricity at the scale of about 105GM/c2. Copyright © 2020, The Authors. All rights reserved.

关键词： Galaxies

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LEIA Discovery of the Longest-lasting and Most Energetic Stellar X-Ray Flare Ever Detected

arXiv

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arXiv 2024年

作者： Mao, Xuan Liu, He-Yang Wang, Song Ling, Zhixing Yuan, Weimin Cheng, Huaqing Pan, Haiwu Li, Dongyue Favata, Fabio Ji, Tuo Zhang, Jujia Zhao, Xinlin Wang, Jing Liu, Mingjun Liu, Yuan Cai, Zhiming Castro-Tirado, Alberto J. Dai, Yanfeng Deng, Licai Ding, Xu Ji, Kaifan Jin, Chichuan Lei, Yajuan Li, Huali Lin, Jun Liu, Huaqiu Liu, Shuai Sun, Hui Sun, Shengli Sun, Xiaojin Shi, Jianrong Wang, Jianguo Wang, Jingxiu Wang, Wenxin Wei, Jianyan Xin, Liping Xiong, Dingrong Zhang, Chen Zhang, Wenda Zhang, Yonghe Zhang, Xiaofeng Zhao, Donghua Zhou, Guiping National Astronomical Observatories Chinese Academy of Sciences Beijing100101 China School of Astronomy and Space Science University of Chinese Academy of Sciences Chinese Academy of Sciences Beijing100049 China Institute for Frontiers in Astronomy and Astrophysics Beijing Normal University Beijing102206 China INAF Osservatorio Astronomico di Palermo Piazza del Parlamento 1 Palermo90134 Italy Department of Physics Imperial College London Exhibition Road LondonSW7 2AZ United Kingdom Polar Research Institute of China Shanghai200136 China Yunnan Observatories Chinese Academy of Sciences Kunming650216 China International Centre of Supernovae Yunnan Key Laboratory Kunming650216 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650216 China Guangxi Key Laboratory for Relativistic Astrophysics School of Physical Science and Technology Guangxi University Nanning530004 China GXU-NAOC Center for Astrophysics and Space Sciences Nanning530004 China Innovation Academy for Microsatellites Chinese Academy of Sciences Shanghai201210 China Granada Spain Unidad Asociada al CSIC Departamentode Ingeniería de Sistemas y Automática Escuela de Ingenierías Universidad de Málaga Málaga Spain Department of Astronomy China West Normal University Nanchong637002 China Center for Astronomical Mega-Science Chinese Academy of Sciences Beijing100012 China Yunnan Key Laboratory of Solar Physics and Space Science Kunming650216 China Shanghai Institute of Technical Physics Chinese Academy of Sciences Shanghai200083 China

The Lobster Eye Imager for Astronomy (LEIA) detected a new X-ray transient on 2022 November 7, identified as a superflare event occurring on a nearby K-type giant star HD 251108. The flux increase was also detected in follow-up observations at X-ray, UV, and optical wavelengths. The flare lasted for about 40 days in soft X-ray observations, reaching a peak luminosity of ∼1.1 × 1034 erg s−1 in 0.5–4.0 keV, which is roughly 60 times the quiescent luminosity. Optical brightening was observed for only one night. The X-ray light curve is well described by a double fast rise and exponential decay model, attributed to the cooling process of a loop arcade structure formed subsequent to the initial large loop with a half-length of ∼1.9 × 1012 cm. Time-resolved X-ray spectra were fitted by a four-temperature apec model (with three components being the quiescent background), showing significant evolution of plasma temperature and emission measure over time. The estimated energy released in the LEIA band is ∼3 × 1039 erg, suggesting that this is likely the most energetic X-ray stellar flare with the longest duration detected to date. © 2024, CC BY.

关键词： Giant stars

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A fast point-pattern matching algorithm based on statistical method

arXiv

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arXiv 2019年

作者： Zhang, Zhen-Jun Zhang, Yi-Gong Cheng, Xiang-Ming Wang, Jian-Cheng Yunnan Observatories Chinese Academy of Sciences Kunming650216 China Key Laboratory of the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650216 China University of Chinese Academy of Sciences Beijing100049 China

We propose a new pattern-matching algorithm for matching CCD images to a stellar catalogue based statistical method in this paper. The method of constructing star pairs can greatly reduce the computational complexity compared with triangle method. We use a subsample of the brightest objects from the image and reference catalogue, and find a coordinate transformation between the image and reference catalogue based on the statistical information of star pairs. Then all the objects are matched based on the initial plate solution. The matching process can be accomplished in several milliseconds for the observed images taken by Yunnan observatory 1-m telescope. Copyright © 2019, The Authors. All rights reserved.

关键词： Stars

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An upgraded interpolator of the radial basis functions network for spectral calculation based on empirical stellar spectral library

arXiv

引用

arXiv 2020年

作者： Cheng, Lian-Tao Zhang, Feng-Hui 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 University of Chinese Academy of Sciences Beijing100049 China

Stellar population synthesis is an important method in the galaxy and star-cluster studies. In the stellar population synthesis models, stellar spectral library is necessary for the integrated spectra of the stellar population. Usually, the stellar spectral library is used to the transformation between the stellar atmospheric parameters and the stellar spectrum. The empirical stellar spectral library has irreplaceable advantages than the theoretical library. However, for the empirical spectral library, the distribution of stars is irregularly in the stellar atmospheric parameter space, this makes the traditional interpolator difficult to get the accurate results. In this work, we will provide an improved radial basis function interpolator which is used to obtain the interpolated stellar spectra based on the empirical stellar spectral library. For this interpolator, we use the relation between the standard variance σ in the Gaussian radial basis function and the density distribution of stars in the stellar atmospheric parameter space to give the prior constraint on this σ. Moreover, we also consider the anisotropic radius basis function by the advantage of the local dispersion of stars in the stellar atmospheric parameter space. Furthermore, we use the empirical stellar spectral library MILES to test this interpolator. On the whole, the interpolator has a good performance except for the edge of the low-temperature region. At last, we compare this interpolator with the work in Cheng et al. (2018), the interpolation result shows an obvious improvement. Users can use this interpolator to get the interpolated spectra based on the stellar spectral library quickly and easily. Copyright © 2020, The Authors. All rights reserved.

关键词： Stars

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Recurring tidal disruption events a decade apart in IRAS F01004-2237

arXiv

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arXiv 2024年

作者： Sun, Luming Jiang, Ning Dou, Liming Shu, Xinwen Zhu, Jiazheng Dong, Subo Buckley, David Cenko, S. Bradley Fan, Xiaohui Gromadzki, Mariusz Liu, Zhu Wang, Jianguo Wang, Tinggui Wang, Yibo Wu, Tao Yang, Lei Zhang, Fabao Zhang, Wenjie Zhang, Xiaer Department of Physics Anhui Normal University Anhui Wuhu241002 China CAS Key Laboratory for Researches in Galaxies and Cosmology Department of Astronomy University of Science and Technology of China Anhui Hefei230026 China School of Astronomy and Space Sciences University of Science and Technology of China Hefei230026 China Center for Astrophysics Guangzhou University Guangzhou510006 China Department of Astronomy School of Physics Peking University 5 Yiheyuan Road Haidian District Beijing100871 China Kavli Institute of Astronomy and Astrophysics Peking University 5 Yiheyuan Road Haidian District Beijing100871 China National Astronomical Observatories Chinese Academy of Science 20A Datun Road Chaoyang District Beijing100101 China South African Astronomical Observatory P.O. Box 9 Observatory Cape Town7935 South Africa Astrophysics Science Division NASA Goddard Space Flight Center MC 661 GreenbeltMD20771 United States Steward Observatory University of Arizona 933 North Cherry Avenue Rm. N204 TucsonAZ85721-0065 United States Astronomical Observatory University of Warsaw Al. Ujazdowskie 4 Warszawa00-478 Poland Max-Planck-Institut für Extraterrestrische Physik Gießenbachstraße 1 Garching85748 Germany Key Laboratory for the Structure and Evolution of Celestial Objects Yunnan Observatories Kunming650011 China

Context. In theory, recurring tidal disruption events (TDEs) may occur when a close stellar binary encounters a supermassive black hole, if one star is captured and undergoes repeating partial TDEs, or if both stars are tidally disrupted (double TDEs). In addition, independent TDEs may be observed over decades in some special galaxies where the TDE rate is extremely high. Exploring the diversity of recurring TDEs and probing their natures with rich observational data help to understand these mechanisms. Aims. We report the discovery of a second optical flare that occurred in September 2021 in IRAS F01004-2237, where the first flare occurred in 2010 has been reported, and present a detailed analysis of multi-band data. We aim to understand the nature of the flare and explore the possible causes of the recurring flares. Methods. We describe our analysis of the position of the flare, the multi-band light curves (LCs), the optical and ultraviolet (UV) spectra, and the X-ray LC and spectra. Results. The position of the flare coincides with the galaxy centre with a precision of 650 pc. The flare peaks in ∼ 50 days with an absolute magnitude of ∼ −21 and fades in two years roughly following L ∝ t−5/3. It maintains a nearly constant blackbody temperature of ∼22,000 K in the late time. Its optical and UV spectra show hydrogen and helium broad emission lines with full width at half maxima of 7,000–21,000 km s−1 and He II/Hα ratio of 0.3–2.3. It shows weak X-ray emission relative to UV emission, with X-ray flares lasting for +1.4. These characters are consistent with a TDE, ruling out the possibilities of a supernova or an active galactic nuclei flare. With a TDE model, we infer a peak UV luminosity of 3.3 ± 0.2 × 1044 erg s−1 and an energy budget of 4.5 ± 0.2 × 1051 erg. Conclusions. A TDE caused the flare that occurred in 2021. The two optical flares separated by 10.3 ± 0.3 years can be interpreted as repeating partial TDEs, double TDEs, or two independent TDEs. Although no

关键词： Budget control

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