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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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Binary evolution and double sequences of blue stragglers in globular clusters

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Proceedings of the International Astronomical Union 2019年第S343期14卷 427-428页

作者： Jiang D. Chen X. Li L. Han Z. Yunnan Observatories Chinese Academy of Sciences 396 Yangfangwang Guandu District Kunming 650216 China Center for Astronomical Mega-Science Chinese Academy of Sciences 20A Datun Road Beijing 100012 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming 650011 China

Binary evolution can produce different blue-straggler binaries, for example, blue stragglers with a bright, red component, or with a faint, blue component. In globular clusters, these blue-straggler binaries are generally observed as a single star, because two components can not be distinguished. Therefore, these blue-straggler binaries can be located in different regions of the color-magnitude diagram of globular clusters, e.g. blue sequence and red sequence observed in M30. We suggest that binary evolution can contribute to the blue stragglers in both of the sequences. Some blue stragglers in the blue sequence may have a faint white dwarf companion, while the red sequence includes some binaries experiencing mass transfer. It should be noted that the red sequence may also have other binaries, for example, the binaries just finished the mass transfer, and the binaries including a blue straggler (the accretors) that have evolved away from the blue sequence. © International Astronomical Union 2019.

关键词： Binaries: General blue stragglers globular clusters stars: evolution

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A time-dependent particle acceleration and emission model: Understanding the particle spectral evolution and blazar flares

arXiv

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arXiv 2020年

作者： Zheng, Y.G. Kang, Shi-Ju Yang, C.Y. Bai, J.M. Department of Physics Yunnan Normal University Kunming650092 China Yunnan Observatories Chinese Academy of Sciences Kunming650011 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences China School of Physics and Electrical Engineering Liupanshui Normal University Liupanshui Guizhou553004 China

The jets of blazars are renowned for their multi-wavelength flares and rapid extreme variability;however, there are still some important unanswered questions about the physical processes responsible for these spectral and temporal changes in emission properties. In this paper, we develop a time-dependent particle evolution model for the time-varying emission spectrum of blazars. In the model, we introduce time-dependent electric and magnetic fields, which consistently include the variability of relevant physical quantities in the transport equation. The evolution on the electron distribution is numerically solved from a generalized transport equation that contains the terms describing the electrostatic, first-order and second-order Fermi acceleration, escape of particles due to both advection and spatial diffusion, as well as energy losses due to the synchrotron emission and inverse-Compton scattering of both synchrotron and external ambient photon fields. We find that the light curve profiles of blazars are consistent with the particle spectral evolution resulting from time-dependent electric and magnetic fields, rather than the effects of the acceleration or the cooling processes. The proposed model is able to simultaneously account for the variability of both the energy spectrum and the light curve profile of the BL Lac object Mrk 421 with reasonable assumptions about the physical parameters. The results strongly indicate that the magnetic field evolution in the dissipated region of a blazar jet can account for the variabilities. Copyright © 2020, The Authors. All rights reserved.

关键词： Emission spectroscopy

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Mass transfer of low-mass binaries and chemical anomalies among unevolved stars in globular clusters

arXiv

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arXiv 2020年

作者： Wei, Dandan Wang, Bo Chen, Xuefei Chen, Hailiang Li, Lifang Jiang, Dengkai 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 Center for Astronomical Mega-Science Chinese Academy of Sciences Beijing100012 China

While it is well known that mass transfer in binaries can pollute the surfaces of the accretors, it is still unclear whether this mechanism can reproduce the observed chemical inhomogeneities in globular clusters. We study the surface abundances of the accretors in low-mass binaries, as a first step towards understanding whether mass transfer in low-mass binaries is one of the potential origins of the aforementioned abundance anomalies in globular clusters. We use the Modules for Experiments in Stellar Astrophysics code to calculate binary evolutionary models with different initial donor masses between 0.9 and 1.9 M for an initial metallicity of Z = 0.0034. The results show that in some low-mass binary systems, the accretors exhibit peculiar chemical patterns when they are still unevolved stars, e.g. C and O depletion;Na and N enhancement;constant Mg, Al and C+N+O. The abundance patterns of the accretors are significantly different from their initial abundances (or that of normal single stars), and can match the observed populations. These abundance patterns strongly depend not only on the initial parameters of binaries (donor mass, mass ratio, and orbital period), but also on the assumptions regarding mass-transfer efficiency and angular momentum loss. These results support the hypothesis that mass transfer in low-mass binaries is at least partly responsible for the unevolved anomalous stars in globular clusters. More work on binary evolutionary models and binary population synthesis is required to fully evaluate the contribution of this scenario. Copyright © 2020, The Authors. All rights reserved.

关键词： Mass transfer

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Binary population synthesis

arXiv

引用

arXiv 2020年

作者： Han, Zhanwen Ge, Hongwei Chen, Xuefei Chen, Hailiang 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 the Chinese Academy of Sciences Beijing100049 China Center for Astronomical Mega-Science Chinese Academy of Sciences Beijing100012 China

Binary interactions lead to the formation of intriguing objects, such as compact binaries, supernovae, gamma ray bursts, X-ray binaries, pulsars, novae, cataclysmic variables, hot subdwarf stars, barium stars, and blue stragglers. To study the evolution of binary populations and the consequent formation of these objects, many methods have been developed over the years, of which a robust approach named binary population synthesis (BPS) warrants special attention. This approach has seen widespread use in many areas of astrophysics, including but not limited to analyses of the stellar content of galaxies, research on galactic chemical evolution, and studies concerning star formation and cosmic re-ionization. In this review, we discuss the role of BPS, its general picture, and the various components that comprise it. We pay special attention to the stability criteria for mass transfer in binaries, as this stability largely determines the fate of binary systems. We conclude with our perspectives regarding the future of this field. Copyright © 2020, The Authors. All rights reserved.

关键词： Supernovae

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The innermost jet in the hidden ultra-luminous X-ray source Cygnus X-3

arXiv

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arXiv 2023年

作者： Yang, Jun García, Federico Palacio, Santiago del Spencer, Ralph Paragi, Zsolt Segura, Noel Castro Gong, Biping Cao, Hongmin Chen, Wen Department of Space Earth and Environment Chalmers University of Technology Onsala Space Observatory OnsalaSE-439 92 Sweden C.C.5 Villa Elisa Buenos Aires Argentina Jodrell Bank Centre for Astrophysics Department of Physics and Astronomy The University of Manchester Oxford Rd. ManchesterM13 9PL United Kingdom Oude Hoogeveensedijk 4 Dwingeloo7991 PD Netherlands School of Physics and Astronomy University of Southampton SouthamptonSO17 1BJ United Kingdom School of Physics Huazhong University of Science and Technology Wuhan430074 China School of Electronic and Electrical Engineering Shangqiu Normal University 298 Wenhua Road Shangqiu Henan476000 China Yunnan Observatories Chinese Academy of Sciences Yunnan Kunming650216 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650216 China

Cygnus X-3 is a high-mass X-ray binary with a compact object accreting matter from a Wolf-Rayet donor star. Recently, it has been revealed by the Imaging X-ray Polarimetry Explorer (IXPE) as a hidden Galactic ultra-luminous X-ray (ULX) source with a luminosity above the Eddington limit along the direction of a narrow (opening angle ∼ 32◦) funnel. In between the IXPE observations, we observed Cyg X-3 with the European VLBI (very long baseline interferometry) Network at 22 GHz and the NICER X-ray instrument. To probe possible relations between the X-ray funnel and the potential radio jet from the ULX, we analyzed the simultaneous multi-wavelength data. Our high-resolution VLBI image reveals an elongated structure with a position angle of −3◦. 2 ± 0◦. 4, accurately perpendicular to the direction of the linear X-ray polarization. Because Cyg X-3 was in the radio quiescent state on 2022 November 10, we identify the mas-scale structure as the innermost radio jet. The finding indicates that the radio jet propagates along and within the funnel. Moreover, the jet is marginally resolved in the transverse direction. This possibly results from the strong stellar winds and the rapid orbital motion of the binary system. Copyright © 2023, The Authors. All rights reserved.

关键词： Stars

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The formation of single neutron-stars from double white-dwarf mergers via accretion-induced collapse

arXiv

引用

arXiv 2020年

作者： Liu, D. Wang, B. 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 Center for Astronomical Mega-Science Chinese Academy of Sciences Beijing100012 China

The merging of double white-dwarfs \(WDs\) may produce the events of accretion-induced collapse \(AIC\) and form single neutron stars \(NSs\). Meanwhile, it is also notable that the recently proposed WD+He subgiant scenario has a significant contribution to the production of massive double WDs, in which the primary WD grows in mass by accreting He-rich material from a He subgiant companion. In this work, we aim to study the binary population synthesis \(BPS\) properties of AIC events from the double WD mergers by considering the classical scenarios and also the contribution of the WD+He subgiant scenario to the formation of double WDs. Firstly, we provided a dense and large model grid of WD+He star systems for producing AIC events through the double WD merger scenario. Secondly, we performed several sets of BPS calculations to obtain the rates and single NS number in our Galaxy. We found that the rates of AIC events from the double WD mergers in the Galaxy are in the range of 1.4−8.9×10−3 yr−1 for all ONe/CO WD+ONe/CO WD mergers, and in the range of 0.3−3.8 × 10−3 yr−1 when double CO WD mergers are not considered. We also found that the number of single NSs from AIC events in our Galaxy may range from 0.382 × 107 to 1.072 × 108. The chirp mass of double WDs for producing AIC events distribute in the range of 0.55−1.25 Mo. We estimated that more than half of double WDs for producing AIC events are capable to be observed by the future space-based gravitational wave detectors. Copyright © 2020, The Authors. All rights reserved.

关键词： Merging

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The afterglow emission from a stratified jet in GRB 170817A

arXiv

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arXiv 2021年

作者： Cheng, Kang-Fa Zhao, Xiao-Hong Zhang, Bin-Bin Bai, Jin-Ming Yunnan Observatories Chinese Academy of Sciences Kunming650216 China University of the Chinese Academy of Sciences Yuquan Road 19 Shijingshan Block Beijing100049 China Center for Astronomical Mega-Science Chinese Academy of Sciences Beijing China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming China School of Astronomy and Space Science Nanjing University Nanjing210093 China Ministry of Education China Department of Physics and Astronomy University of Nevada Las VegasNV89154 United States

The afterglow of GRB 170817A has been detected for more than three years, but the origin of the multi-band afterglow light curves remains under debate. A classical top-hat jet model is faced with difficulties in producing a shallow rise of the afterglow light curves as observed (Fν ∝ T0.8). Here we reconsider the model of stratified ejecta with energy profile of E(> Γβ) = E0(Γβ)-k as the origin of the afterglow light curves of the burst, where Γ and β are the Lorentz factor and speed of the ejecta, respectively. k is the power-law slope of the energy profile. We consider the ejecta are collimated into jets. Two kinds of jet evolutions are investigated, including a lateral-spreading jet and a non-lateral-spreading jet. We fit the multi-band afterglow light curves, including the X-ray data at one thousand days post-burst, and find that both the models of the spreading and non-spreading jets can fit the light curves well, but the observed angular size of the source and the apparent velocity of the flux centroid for the spreading jet model are beyond the observation limits, while the non-spreading jet model meets the observation limits. Some of the best-fit parameters for the non-spreading jet model, such as the number density of the circumburst medium ∼ 10-2 cm-3 and the total jet kinetic energy E ∼ 4.8 × 1051 erg, also appear plausible. The best-fit slope of the jet energy profile is k ∼ 7.1. Our results suggest that the afterglow of GRB 170817A may arise from the stratified jet and that the lateral spreading of the jet is not significant. Copyright © 2021, The Authors. All rights reserved.

关键词： Kinetic energy

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Long-Term Light and Period Variations in the Supersoft X-Ray Source V617 Sgr

SSRN

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SSRN 2023年

作者： Zang, Lei Zhao, Ergang Fernández-Lajús, Eduardo Zubairi, Ahmed Waqas Sarotsakulchai, Nopphadon P. O. Box 110 Kunming650216 China Key Laboratory of the Structure and Evolution of Celestial Objects Chinese Academy of Sciences P. O. Box 110 Kunming650216 China University of Chinese Academy of Sciences No.1 Yanqihu East Rd Huairou District Beijing101408 China Center for Astronomical Mega-Science Chinese Academy of Sciences 20A Datun Road Chaoyang District Beijing100012 China Facultad de Ciencias Astronómicas y Geofísicas Universidad Nacional de La Plata Paseo del Bosque S/N La PlataB1900FWA Argentina La PlataB1900FWA Argentina National Astronomical Research Institute of Thailand 260 Moo 4 T. Donkaew A. Maerim Chiangmai50180 Thailand

V617 Sgr is one of the Galactic counterparts of supersoft X-ray sources as a member of the V Sagittae class, where a massive white dwarf is accreting material from its stellar companion and forming an accretion disk. Since 2014, we have monitored it for about nine years with the 2.15m telescope at CASLEO. It is found that the light curve shows obviously fluctuations and flickering, which imply the presence of actively hot spots on the accretion disk. Meanwhile, the flat-bottomed depressions can be explained by the presence of circumbinary material. By collecting all available eclipse times from the literature together with 149 newly determined times of light minimum, we constructed the O-C diagram and analyzed the variations in the orbital period of the eclipsing binary V617 Sgr. It is confirmed that the orbital period is increasing continuously with a rate of dP/dt=+1.68(3)E-7d/yr=+0.0145(3)s/yr. A cyclic variation is detected to be superimposed on the period increase with an amplitude of 4.6min and a period of 26yr. The continuous period increase is largely due to mass transfer from the donor secondary on its Kelvin–Helmholtz time-scale, while wind mass loss from the accretion disk surrounding the white dwarf may also contribute on the period change. In this case, the mass-transfer rate of V617 Sgr is estimated to be in the range of about 0.575E-6 to 2.25E-6Msun/yr and the mass-accretion rate is less than 1.59E-6Msun/yr. The cyclic change can be explained by the presence of a third body or magnetic activity cycles of the secondary. © 2023, The Authors. All rights reserved.

关键词： Mass transfer

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

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The Astrophysical Journal Supplement Series 2025年第2期278卷 46-46页

作者： Sufen Guo Mikhail Kovalev Jiao Li Guoliang Lü Shi Jia Zhenwei Li Jiangdan Li Jianping Xiong Mingkuan Yang Tongyu He Xuefei Chen Zhanwen Han School of Physical Science and Technology Xinjiang University Urumqi 830046 People’s Republic of China Yunnan Observatories Chinese Academy of Sciences (CAS) Kunming 650216 People’s Republic of China lijiao@*** zhanwenhan@*** Key Laboratory for the Structure and Evolution of Celestial Objects CAS Kunming 650216 People’s Republic of China International Centre of Supernovae (ICESUN) Yunnan Key Laboratory of Supernova Research Yunnan Observatories Chinese Academy of Sciences (CAS) Kunming 650216 People’s Republic of China Key Laboratory of Optical Astronomy National Astronomical Observatories Chinese Academy of Sciences Beijing 100101 People’s Republic of China College of Physics Science and Technology Hebei University Baoding 071002 People’s Republic of 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 medium-resolution spectroscopic survey, we derived orbital solutions for 665 SB 2 binaries by fitting the radial velocities of 1119 SB 2 systems with at least six observations, employing a modified version of The Joker optimized for SB 2 binaries. To ensure the reliability of the results, four selection criteria were applied: reduced chi-square, normalized mean absolute error, maximum phase gap, and radial velocity distribution metric. After applying these criteria, 665 reliable orbits were retained. Comparison with Kepler, TESS, and Zwicky Transient Facility 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 SB 1 systems in Gaia data. These orbital solutions contribute to understanding binary star evolution and the statistical properties of binary populations.

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