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Contact binaries at different evolutionary stages

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Research in Astronomy and Astrophysics 2020年第10期20卷 229-248页

作者： Sheng-Bang Qian Li-Ying Zhu Liang Liu Xu-Dong Zhang Xiang-Dong Shi Jia-Jia He Jia Zhang Yunnan Observatories Chinese Academy of SciencesKunming 650216China School of Physics and Astronomy Yunnan UniversityKunming 650091China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of SciencesKunming 650216China Center for Astronomical Mega-Science Chinese Academy of SciencesBeijing 100101China University of Chinese Academy of Sciences Beijing 100049China

Contact binaries consist of two strongly interacting component stars where they are filling their critical Roche lobes and sharing a common *** of them are main-sequence stars,but some of them are post main-sequence *** are good astrophysical laboratories for studying several problems such as the merging of binary stars,evolution of the common envelope,the origin of luminous red nova outbursts and the formation of rapidly rotating single stars with possible planetary systems.A large number of contact binary candidates were detected by several photometric surveys around the world and many of them were observed by the LAMOST spectroscopic *** on follow-up observations,the evolutionary states and geometrical structures of some systems were understood *** this review,we will introduce and catalog new stellar atmospheric parameters(i.e.,the effective temperature(Teff),the gravitational acceleration(log(g)),metallicity([Fe/H])and radial velocity(Vr))for 9149 EW-type contact binaries that were obtained based on low-and medium-resolution spectroscopic surveys of *** we will focus on several groups of contact binary stars,i.e.,marginal contact binary systems,deep and low-mass ratio contact binary stars,binary systems below the short-period limit of contact binaries and evolved contact *** contact binaries are at the beginning of the contact stage,while deep and low-mass ratio contact binary stars are at the final evolutionary stage of tidally locked *** statistical relations including the period-temperature relation are determined well by applying LAMOST data and their formation and evolutionary states are *** period-color relation of M-type binaries reveals that there are contact binaries below the short-period *** for and investigating contact binaries near and below this limit will help us to understand the formation of contact binary systems and a new prediction for the short-period l

关键词： binaries:eclipsing stars:late-type stars:low-mass stars:formation stars:evolution

Detection of Contact Binary Candidates Observed By TESS Using Autoencoder Neural Network

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arXiv 2024年

作者： Ding, Xu Song, ZhiMing Wang, ChuanJun Ji, KaiFan 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 Center for Astronomical Mega-Science Chinese Academy of Sciences 20A Datun Road Chaoyang District Beijing100012 China School of Information Yunnan University of Finance and Economics Kunming China Yunnan Key Laboratory of Service Computing Kunming China University of the Chinese Academy of Sciences Yuquan Road 19# Shijingshan Block Beijing100049 China

Contact binary may be the progenitor of a red nova that eventually produces a merger event and have a cut-off period around 0.2 days. Therefore, a large number of contact binaries is needed to search for the progenitor of red novae and to study the characteristics of short-period contact binaries. In this paper, we employ the Phoebe program to generate a large number of light curves based on the fundamental parameters of contact binaries. Using these light curves as samples, an autoencoder model is trained, which can reconstruct the light curves of contact binaries very well. When the error between the output light curve from the model and the input light curve is large, it may be due to other types of variable stars. The goodness of fit (R2) between the output light curve from the model and the input light curve is calculated. Based on the thresholds for global goodness of fit (R2), period, range magnitude, and local goodness of fit (R2), a total of 1322 target candidates were obtained. © 2024, CC BY.

关键词： Stars

Precision Determination of Scintillation Screen Parameters from Annual Modulation Measurement of Pulsar Scintillation Arc Curvature with the FAST Telescope

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arXiv 2025年

作者： Huang, Yuanshang Shi, Xun Yao, Jumei Zhu, Weiwei Xu, Yonghua Yunnan University Kunming650500 China Xinjiang Astronomical Observatory Chinese Academy of Sciences 150 Science 1-Street Xinjiang Urumqi830011 China Key Laboratory of radio Astronomy Chinese Academy of Sciences Xinjiang Urumqi830011 China Xinjiang Key Laboratory of radio Astrophysics 150 Science1-Street Xinjiang Urumqi830011 China National Astronomical Observatories Chinese Academy of Sciences Beijing100101 China Institute for Frontiers in Astronomy and Astrophysics Beijing Normal University Beijing102206 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

Pulsar scintillation observations have revealed ubiquitous discrete scintillation screens in the interstellar medium. A major obstacle in identifying the nature of these screens is the uncertainty in their distances, which prevents precise correlation with known structures in the Milky Way. We used the Five-hundred-meter Aperture Spherical radio Telescope (FAST) to observe PSR B1237+25, PSR 1842+14, and PSR 2021+51. We detected 10 scintillation arcs in PSR B1237+25, 1 in PSR 1842+14, and at least 6 in PSR 2021+51. By modeling the annual modulation of these scintillation arcs, we constrained the distances of the scintillation screens, as well as the anisotropic scattering directions and the projected velocities in those directions. The scintillation screens are distributed throughout the entire paths between Earth and the pulsars. Among these, the distance to the main scintillation screen toward PSR B1237+25 is 267+32−28 pc, the scintillation screen toward PSR B1842+14 is at a distance of 240+210−120 pc, and the main scintillation screen toward PSR B2021+51 is located at 887+167−132 pc. Several screens in our sample appear at distances coinciding with the Local Bubble boundary, particularly the brightest scintillation arc toward PSR B1237+25. We provide a substantial sample of scintillation screen measurements, revealing the rich plasma density fluctuation structures present in the Milky Way. Copyright © 2025, The Authors. All rights reserved.

关键词： Pulsars

A Linear Decomposition Method to Analyze and Study Pulsar Mode Changes

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arXiv 2025年

作者： Hao, Longfei Li, Zhixuan Shen, Faxin Xu, Yonghua Huang, Yuxiang Lee, Kejia Yu, Qingzheng Wang, Hongguang Yunnan Observatories Chinese Academy of Sciences Kunming650216 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650216 China Department of Astronomy School of physics Peking University Beijing100871 China National Astronomical Observatory Chinese Academy of Sciences Beijing100101 China Beijing Laser Acceleration Innovation Center Huairou Beijing101400 China Department of Astronomy Xiamen University Xiamen361005 China School of Physics and Electronic Engineering Guangzhou University Guangzhou510006 China

In this paper, we present the linear decomposition method (LDM), which we developed to detect and analyze pulsar profile variations and mode changing behaviour. We developed LDM utilizing the likelihood function approach assuming the Gaussian noise. The LDM projects pulse profiles onto significance-ordered orthonormal vector bases. We show that the method is similar to the principal component analysis (PCA), but LDM can handle more general situations. We use simulated dataset and data from the Kunming 40-m radio telescope to demonstrate the application of the LDM. We found that the LDM successfully identified mode changes for well-known mode-changing PSR B0329+54 and found a continuous pulse profile evolution for PSR B0355+54 . We also show that the LDM can be used to improve the timing precision for mode changing PSR B0329+54. Copyright © 2025, The Authors. All rights reserved.

关键词： Pulsars

MHD simulations of inward shocks in Cassiopeia A

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Research in Astronomy and Astrophysics 2020年第4期20卷 39-43页

作者： Chu-Yuan Yang Bi-Wen Bao Si-Ming Liu Yunnan Observatories Chinese Academy of SciencesKunming 650216China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of SciencesKunming 650216China Center for Astronomical Mega-Science Chinese Academy of SciencesBeijing 100101China Department of Astronomy Key Laboratory of Astroparticle Physics of Yunnan ProvinceYunnan UniversityKunming 650091China Key Laboratory of Dark Matter and Space Astronomy Purple Mountain ObservatoryChinese Academy of SciencesNanjing 210033China

Cassiopeia A,the brightest radio supernova remnant(SNR)in the sky,has several unique characteristics in comparison to its *** its radio brightness and prominent soft-concave radio spectrum,itsγ-ray spectrum appears to have a low-energy cutoff near 2 GeV,and it is the only SNR with prominent hard X-ray *** the unusual radio properties may be attributed to strong emission from reverse shocks,the hard X-ray emission has been associated with high-speed inward shocks induced by high density ***,the low-energyγ-ray spectral cutoff could be attributed to slow penetration of lower energy particles accelerated near the inward shocks into high-density emission *** this paper,we carry out magneto-hydrodynamic(MHD)simulations of shocks in Cassiopeia A and demonstrate that its inward shock structure can indeed be reproduced via shock interactions with clumps of gases with a density of 20 cm-3.

关键词： acceleration of particles supernovae:individual(Cassiopeia A) ISM:supernova remnants X-rays:ISM

Astronomical Site Monitoring System at Lijiang Observatory

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Research in Astronomy and Astrophysics 2020年第9期20卷 291-308页

作者： Yu-Xin Xin Jin-Ming Bai Bao-Li Lun Yu-Feng Fan Chuan-Jun Wang Xiao-Wei Liu Xiao Guang Yu Kai Ye Teng-Fei Song Liang Chang Shou-Sheng He Jji-Rong Mao Liang Xu Ding-Rong Xiong Xi-Liang Zhang Jian-Guo Wang Xu Ding Hai-Cheng Feng Xiang-Kun Liu Yang Huang Bing-Qiu Chen Yunnan Observatories Chinese Academy of SciencesKunming 650216China University of Chinese Academy of Sciences Beijing 100049China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of SciencesKunming 650216China Center for Astronomical Mega-Sciences Chinese Academy of SciencesBeijing 100101China South-Western Institute for Astronomy Research Yunnan UiversityKunming 650500China

We installed two sets of Astronomical Site Monitoring Systems(ASMSs)at Lijiang Observatory(GMG),for the running of the 2.4-meter Lijiang optical telescope(LJT)and the 1.6-meter Multi-channel Photometric Survey Telescope(Mephisto).The Mephisto is under *** ASMS has been running on robotic mode since *** core instruments:Cloud Sensor,All-Sky Camera and AutonomousDIMM that are developed by our group,together with the commercial Meteorological Station and Sky Quality Meter,are combined into the astronomical optical site monitoring *** new Cloud Sensor's Cloud-Clear Relationship is presented for the first time,which is used to calculate the All-Sky cloud *** designed the Autonomous-DIMM located on a tower,with the same height as *** seeing data have been observed for a full ***'s data for the year 2019 are also analysed in detail,which are valuable to observers.

关键词： Astronomical Site Monitoring System Lijiang Observatory Cloud Sensor Autonomous-DIMM

Prominence activation, optical flare, and post-flare loops on the RS Canum Venaticorum star SZ Piscium

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arXiv 2024年

作者： Cao, Dongtao Gu, Shenghong Ge, Jian Wang, Tinggui Zhou, Jilin Chang, Liang Wolter, U. Mittag, M. Schmitt, J.H.M.M. Perdelwitz, V. 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 Astronomy University of Florida Bryant Space Science Center GainesvilleFL32611 United States Key Laboratory for Research in Galaxies and Cosmology Department of Astronomy University of Science and Technology of China Chinese Academy of Sciences Hefei230026 China Department of Astronomy Key Laboratory of Modern Astronomy and Astrophysics in Ministry of Education Nanjing University Nanjing210093 China Hamburger Sternwarte Universität Hamburg Hamburg21029 Germany

We present the results of time-resolved high-resolution spectroscopic observations of the very active RS Canum Venaticorum (RS CVn) star SZ Piscium (SZ Psc), obtained during two consecutive observing nights on October 24 and 25, 2011. Several optical chromospheric activity indicators are analyzed using the spectral subtraction tech- nique, which show the remarkably different behavior between two nights. Gradually blue-shifted and strengthened excess absorption features presented in the series of the subtracted spectra (especially for the Hα, He i D3 and Hβ lines), as a result of active stellar prominence that is rising its height along the line of our sight, was detected in the observations on October 24. This prominence activation event was probably associated with the subsequently occurred optical flare, and part of that flare decay phase was hunted in the observations on October 25. The flare was characterized by the prominent He i D3 line emission, as well as stronger chromospheric emission in the Hα, Hβ and other active lines. The gradual decay of flare was accompanied by an obviously developmental absorption feature in the blue wing of the H_ and other active lines, which could be explained as cool post-flare loops which projected against the bright flare background. Therefore, a series of possibly associated magnetic activity phenomena, including flare-related prominence activation, optical flare and post-flare loops, were detected during our observations. Copyright © 2024, The Authors. All rights reserved.

关键词： Chemical activation

Temporal variability and obscuration effects in the X-ray emission of classical nova V339 Delphini (Nova Delphini 2013)

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arXiv 2025年

作者： Pei, Songpeng Ospina, Nataly Zhang, Xiaowan Li, Qiang Ou, Ziwei Yang, Taozhi Cai, Yongzhi School of Physics and Electrical Engineering Liupanshui Normal University Guizhou Liupanshui553004 China Department of Theoretical Physics University Autonoma Madrid Madrid28049 Spain Qiannan Normal University for Nationalities Duyun558000 China Qiannan Key Laboratory of Radio Astronomy Guizhou Province Duyun558000 China Tsung-Dao Lee Institute Shanghai Jiao Tong University Shanghai201210 China Ministry of Education Key Laboratory for Nonequilibrium Synthesis and Modulation of Condensed Matter School of Physics Xi’an Jiaotong University Xi’an710049 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

In this study, we present a detailed analysis of public archival soft X-ray data on the classical nova V339 Delphini (Nova Del 2013) during its outburst, obtained using the Chandra High-Resolution Camera Spectrometer (HRC-S) and Low Energy Transmission Grating (LETG), as well as XMM-Newton in 2013. The observations, spanning from day 85.2 to day 112.0 after the optical maximum, capture the nova during its luminous supersoft X-ray source (SSS) phase. The spectra reveal numerous absorption features with blue-shifted velocities ranging from ∼ 724 to ∼ 1474 km s−1, with the majority of lines blue-shifted by approximately 1200 km s−1. We confirm the presence of a short-period modulation of the X-ray flux with a period of approximately 54 seconds, as well as the drift of this period, which was detected on days 97.0 and 112.0 during the outburst with both XMM-Newton and Chandra. This period modulation is transient in nature, with significant variations in amplitude and pulse profile over timescales of a few thousand seconds, likely due to temporary obscuration events that affect the emission from the central hot source. The pulse profiles exhibit substantial deviations from a pure sinusoidal shape, which may be related to the period drift. Additionally, the modulation amplitude shows a possible anti-correlation with the count rates on day 97.0, likely also caused by temporary obscuration events influencing the central source’s emission. Copyright © 2025, The Authors. All rights reserved.

关键词： White dwarfs

Generalized split monopole magnetospheres: The effects of current sheets

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Physical Review D 2021年第2期104卷 023009-023009页

作者： Huiquan Li Jiancheng Wang Yunnan Observatories Chinese Academy of Sciences 650216 Kunming China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences 650216 Kunming China and Center for Astronomical Mega-Science Chinese Academy of Sciences 100012 Beijing 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 decentered 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 .

关键词： Neutron stars & pulsars