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arXiv 2024年

作者： Feng, Hai-Cheng Li, Rui Napolitano, Nicola R. Li, Sha-Sha Bai, J.M. Li, Ran Liu, H.T. Lu, Kai-Xing Radovich, Mario Shan, Huan-Yuan Wang, Jian-Guo Xi, Wen-Zhe Xie, Ling-Hua Zhang, Yang-Wei Yunnan Observatories Chinese Academy of Sciences Yunnan Kunming650216 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Yunnan Kunming650216 China Center for Astronomical Mega-Science Chinese Academy of Sciences 20A Datun Road Chaoyang District Beijing100012 China Key Laboratory of Radio Astronomy and Technology Chinese Academy of Sciences 20A Datun Road Chaoyang District Beijing100101 China Institude for Astrophysics School of Physics Zhengzhou University Zhengzhou450001 China School of Physics and Astronomy Sun Yat-sen University Zhuhai Campus 2 Daxue Road Xiangzhou District Zhuhai China CSST Science Center for Guangdong-Hong Kong-Macau Great Bay Area Zhuhai519082 China INAF Osservatorio Astronomico di Capodimonte Salita Moiariello 16 Napoli80131 Italy University of Chinese Academy of Sciences Beijing100049 China National Astronomical Observatories Chinese Academy of Sciences 20A Datun Road Chaoyang District Beijing100012 China INAF Osservatorio Astronomico di Padova via dell’Osservatorio 5 Padova35122 Italy Shanghai Astronomical Observatory Chinese Academy of Sciences Shanghai200030 China South-Western Institute for Astronomy Research Yunnan University Kunming650500 China

We present a novel multimodal neural network for classifying astronomical sources in multiband ground-based observations, from optical to near infrared, to separate sources in stars, galaxies and quasars. Our approach combines a convolutional neural network branch for learning morphological features from r-band images with an artificial neural network branch for extracting spectral energy distribution (SED) information. Specifically, we have used 9-band optical (ugri) and NIR (ZY HJKs) data from the Kilo-Degree Survey (KiDS) Data Release 5. The two branches of the network are concatenated and feed into fully-connected layers for final classification. We train the network on a spectroscopically confirmed sample from the Sloan Digital Sky Survey cross-matched with KiDS. The trained model achieves 98.76% overall accuracy on an independent testing dataset, with F1 scores exceeding 95% for each class. Raising the output probability threshold, we obtain higher purity at the cost of a lower completeness. We have also validated the network using external catalogs cross-matched with KiDS, correctly classifying 99.74% of a pure star sample selected from Gaia parallaxes and proper motions, and 99.74% of an external galaxy sample from the Galaxy and Mass Assembly survey, adjusted for low-redshift contamination. We apply the trained network to 27,334,751 KiDS DR5 sources with r ≤ 23 mag to generate a new classification catalog. This multimodal neural network successfully leverages both morphological and SED information to enable efficient and robust classification of stars, quasars, and galaxies in large photometric surveys. © 2024, CC BY.

关键词： Classification (of information)

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Long-term evolution of post-explosion Helium-star Companions of Type Iax Supernovae

arXiv

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arXiv 2022年

作者： Zeng, Yaotian Liu, Zheng-Wei Heger, Alexander McCully, Curtis Röpke, Friedrich K. Han, Zhanwen Kunming650216 China Key Laboratory for the Structure and Evolution of Celestial Objects CAS Kunming650216 China University of Chinese Academy of Science Beijing100012 China Center for Astronomical Mega-Science CAS Beijing100012 China School of Physics and Astronomy Monash University 19 Rainforest Walk VIC3800 Australia Joint Institute for Nuclear Astrophysics National Superconducting Cyclotron Laboratory Michigan State University 1 Cyclotron Laboratory East LansingMI48824-1321 United States ClaytonVIC3800 Australia Stromlo ACT2611 Australia Las Cumbres Observatory 6740 Cortona Dr Ste 102 GoletaCA93117-5575 United States Department of Physics University of California Santa BarbaraCA93106-9530 United States Zentrum für Astronomie Universität Heidelberg Institut für Theoretische Astrophysik Philosophenweg 12 HeidelbergD-69120 Germany Heidelberger Institut für Theoretische Studien Schloss-Wolfsbrunnenweg 35 HeidelbergD-69118 Germany

Supernovae of Type Iax (SNe Iax) are an accepted faint subclass of hydrogen-free supernovae. Their origin, the nature of the progenitor systems, however, is an open question. Recent studies suggest that the weak deflagration explosion of a near-Chandrasekhar-mass white dwarf in a binary system with a helium star donor could be the origin of SNe Iax. In this scenario, the helium star donor is expected to survive the explosion. We use the one-dimensional stellar evolution codes MESA and Kepler to follow the post-impact evolution of the surviving helium companion stars. The stellar models are based on our previous hydrodynamical simulations of ejecta-donor interaction, and we explore the observational characteristics of these surviving helium companions. We find that the luminosities of the surviving helium companions increase significantly after the impact: They could vary from 2,500 Lo to 16,000 Lo for a Kelvin-Helmholtz timescale of about 104 yr. After the star reaches thermal equilibrium, it evolves as an O-type hot subdwarf (sdO) star and continues its evolution along the evolutionary track of a normal sdO star with the same mass. Our results will help to identify the surviving helium companions of SNe Iax in future observations and to place new constraints on their progenitor models. Copyright © 2022, The Authors. All rights reserved.

关键词： Helium

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Accreting CO material onto ONe white dwarfs towards accretion-induced collapse

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Research in Astronomy and Astrophysics 2018年第3期18卷 121-128页

作者： Cheng-Yuan Wu Bo Wang Yunnan Observatories Chinese Academy of Sciences Kunming 650216 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming 650216 China University of Chinese Academy of Sciences Beijing 100049 China Center for Astronomical Mega-Science Chinese Academy of Sciences Beijing 100012 China

The final outcomes of accreting ONe white dwarfs（ONe WDs） have been studied for several decades,but there are still some issues that are not resolved. Recently,some studies suggested that the deflagration of oxygen would occur for accreting ONe WDs with Chandrasekhar masses. In this paper,we aim to investigate whether ONe WDs can experience accretion-induced collapse（AIC） or explosions when their masses approach the Chandrasekhar limit. Employing the stellar evolution code Modules for Experiments in Stellar Astrophysics（MESA）,we simulate the longterm evolution of ONe WDs with accreting CO material. The ONe WDs undergo weak multicycle carbon flashes during the mass-accretion process,leading to mass increase of the WDs. We found that different initial WD masses and mass-accretion rates influence the evolution of central density and temperature. However,the central temperature cannot reach the explosive oxygen ignition temperature due to neutrino cooling. This work implies that the final outcome of accreting ONe WDs is electroncapture induced collapse rather than thermonuclear explosion.

关键词： stars evolution - binaries close - supernovae general - white dwarfs

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Cataclysmic variables based on the stellar spectral survey LAMOST DR3

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Research in Astronomy and Astrophysics 2018年第6期18卷 67-88页

作者： Xianming L.Han Li-Yun Zhang Jian-Rong Shi Qing-Feng Pi Hong-Peng Lu Li-Bo Zhao Rachel K.Terheide Lin-Yang Jiang College of Physics/Department of Physics and Astronomy & Guizhou Provincial Key Laboratory of Public Big Data Guizhou University Dept.of Physics and Astronomy Butler University Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences National Astronomical Observatories Chinese Academy of Sciences Department of Astronomy Beijing Normal University

Big data in the form of stellar spectra from the spectroscopic survey associated with the Large Sky Area Multi-object Fiber Spectroscopic Telescope(LAMOST) are important for studying properties of cataclysmic variables(CVs). By cross matching the catalogs of CVs compiled with LAMOST DR3,acquired from October 2011 to July 2015, we obtained the first spectroscopic catalog for CVs observed by LAMOST with high signal to noise ratio, above 8. By integrating line profiles, their equivalent widths(EWs) of the Hα, Hβ, Hγ and Hδ, as well as He I 5876 and 6678 A? lines, were calculated. There were74 stellar spectra from 48 known CVs and three spectra from three new CV candidates. At the same time, we also collected their previously published EWs. Thirty-three objects had repeated spectra and30 stars showed spectral variability in the Hα line. Moreover, we carried out photometric follow-up studies for five CVs(UU Aqr, TT Tri, PX And, BP Lyn and RW Tri). We obtained nine new light curves and revised their linear ephemerides. For RW Tri, there is a possible oscillation with an amplitude of0.0031(2) days and a period of 47.6±0.4 years, which might be caused by a third body(brown dwarf)or magnetic activity cycle.

关键词： stars: cataclysmic variables stars: spectroscopic stars: variable

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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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Hemispheric Distribution of Solar Active Regions During Solar Cycles 23-25

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The Astrophysical Journal Supplement Series 2025年第2期278卷 48-48页

作者： Yuxia Liu Tingting Xu Miao Wan Linhua Deng Xinhua Zhao Shiyang Qi Nanbin Xiang Weihong Zhou School of Mathematics and Computer Science Yunnan Minzu University Kunming Yunnan 650504 People’s Republic of China zwh@*** State Key Laboratory of Space Weather National Space Science Center Chinese Academy of Sciences Beijing 100190 People’s Republic of China Radio Science and Technology Center (π Center) Chengdu Sichuan 610041 People’s Republic of China College of Science Henan Agricultural University Zhengzhou Henan 450002 People’s Republic of China Yunnan Observatories Chinese Academy of Sciences Kunming Yunnan 650216 People’s Republic of China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming Yunnan 650216 People’s Republic of China

Solar active regions (ARs) are crucial for understanding the long-term evolution of solar activities and predicting eruptive phenomena, including solar flares and coronal mass ejections. However, the cycle-dependent properties in the north-south asymmetry of ARs have not been fully understood. In this study, we investigate the hemispheric distribution of ARs from Carrington Rotation 1909 to 2278 (between 1996 May and 2023 November) by using three parameters that describe the magnetic field distribution of ARs: number, area, and flux. The main findings are as follows: (1) The three AR parameters show significant hemispheric asymmetry in cycles 23-25. The strong correlation between AR area and flux indicates that they can better reflect the intrinsic properties of solar magnetic field. (2) The correlation between sunspot activity and AR parameters varies in the two hemispheres across the different cycles. The AR parameters provide additional information for the variations in sunspot activity, which can better predict the intensity and cyclical changes of solar activity. (3) The variation in the fitting slope sign of the asymmetry index for AR parameters reflects periodic changes in hemispheric ARs, providing valuable insights into the activity of other stars. (4) Both the dominant hemisphere and the cumulative trend of AR parameters display a cycle-dependent behavior. Moreover, the trend variations of AR area and flux are similar, reflecting the long-term evolutionary characteristics of solar magnetic field. Our analysis results are relevant for understanding the hemispheric coupling of solar magnetic activity and its cyclic evolutionary patterns.

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NSVS 01286630:a detached binary with a close-in companion

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Research in Astronomy and Astrophysics 2018年第9期18卷 123-132页

作者： Bin Zhang Sheng-Bang Qian Nian-Ping Liu Wen-Ping Liao Li-Ying Zhu Ai-Jun Dong Qi-Jun Zhi Yunnan Observatories Chinese Academy of SciencesKunming 650216China Key Laboratory of the Structure and Evolution of Celestial Objects Chinese Academy of SciencesKunming 650216China University of Chinese Academy of Sciences Beijing 100049China School of Physics and Electronic Science Guizhou Normal UniversityGuiyang 550001China

New photometric observations of NS VS 01286630 were performed and two sets of fourcolor（B, V, Rc, Ic） light curves（LCs） were obtained. Using the 2013 version of the Wilson-Devinney（W-D） code, we analyzed these data. The photometric solutions reveal that NS VS 01286630 is an active detached eclipsing binary（EB） with a high orbital inclination（nearly 90°）. Remarkably, the temperature of the primary component（the hotter star） is higher than the secondary one, but the value of mass ratio q（M2/M1）for NS VS 0128663 is more than 1, which can be explained in that the surface of the secondary component of NSVS 01286630 is covered with big cool starspots. Based on our new CCD mid-eclipse times and the data published until now, variations in the mid-eclipse times were reanalyzed in detail using a weighted least-squares method. It is discovered that the（O-C） diagram of the system shows a cyclic oscillation with a period of 3.61 yr and an amplitude of 0.001 d. The cyclic variation may be caused by the light-travel time effect（LTTE） due to the presence of a third companion, whose mass we calculated as M3 sin（i3） =0.11 M（⊙）. The third body may affect the orbital evolution of the central binary system by transferring angular momentum.

关键词： stars binaries close- stars binaries eclipsing-stars individual （NSVS 01286630）

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High amplitude δ Scuti star BO Lyn with evidence of a late A-type companion in an elliptical orbit

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Research in Astronomy and Astrophysics 2018年第1期18卷 119-126页

作者： Lin-Jia Li Sheng-Bang Qian Jia Zhang Li-Ying Zhu Wen-Ping Liao 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 Center for Astronomical Mega-Science Chinese Academy of Sciences Beijing 100012 China University of Chinese Academy of Sciences Beijing 100049 China

We present 145 times of light maximum for high amplitude δ Scuti star BO Lyn based on several sky surveys（CRTS,DASCH,NSVS,OMC and Super WASP）and our photometric *** with the data in literature,a total of 179 times of light maximum are used to analyze the O-C diagram of BO *** find that it can be described by an upward parabolic component and a periodic variation with a period of 34.5±0.1 *** latter could be caused by the light travel time effect as a result of an additional companion orbiting in a highly elliptical orbit（e=0.64±0.03）.Our study indicates that the companion’s luminosity cannot be ignored,and it should be a late A-type main-sequence *** long-term period change of BO Lyn is also detected,and its value,1.52±0.26×10^（-3）d Myr^（-1）,is consistent with evolutionary *** suggest that more spectroscopic and photometric observations are needed in the future to confirm the nature of the BO Lyn system.

关键词： techniques：photometric stars：variables：δ Scuti stars：individual（BO Lyn）

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Stellar populations of a sample of optically selected AGN-host dwarf galaxies

arXiv

引用

arXiv 2020年

作者： Cai, Wei Zhao, Yinghe Zhang, Hong-Xin Bai, Jin-Ming Liu, Hong-Tao Yunnan Observatories Chinese Academy of Sciences Kunming652016 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 Center for Astronomical Mega-Science Chinese Academy of Sciences Beijing100012 China CAS Key Laboratory for Research in Galaxies and Cosmology Department of Astronomy University of Science and Technology of China Hefei Anhui230026 China

In this paper we present our studies on the stellar populations and star formation histories (SFHs) for the Reines et al. sample of 136 dwarf galaxies which host active galactic nuclei (AGNs), selected from the Sloan Digital Sky Survey Data Release 8. We derive stellar populations and reconstruct SFHs for these AGN-host dwarfs using the stellar population synthesis code STARLIGHT. Our results suggest that these AGN-host dwarfs have assembled their stellar masses within a narrow period of time with the stellar mass-weighted ages in the range of 109 − 1010 yr, but show a wide diversity of SFHs with the luminosity-weighted stellar ages in the range of 107 − 1010 yr. The old population (t > 109 yr) contributes most to the galaxy light for the majority of the sample;the young population (t 8 yr) also appears in significant but widely varying fractions, while the intermediate-age population (108 9 yr) in general contributes less to the optical continuum at 4020 Å. We also find that these dwarfs follow a similar mass-metallicity relation to normal star-forming galaxies, indicating that AGNs have little effect on the chemical evolution of the host galaxy. We further investigate the relation between the derived SFHs and morphology of the host galaxy, and find no correlation. Comparing the SFHs with the luminosity of the [O iii] λ5007 line (L[O iii]), we find that there exists a mild correlation when L[O iii] > 1039 erg s−1, indicating that there is a physical connection between star formation and AGN activities in these dwarf galaxies. Copyright © 2020, The Authors. All rights reserved.

关键词： Galaxies

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Astronomical site monitoring system at lijiang observatory

arXiv

引用

arXiv 2020年

作者： Xin, Yu-Xin Bai, Jin-Ming Lun, Bao-Li Fan, Yu-Feng Wang, Chuan-Jun Liu, Xiao-Wei Yu, Xiao-Guang Ye, Kai Song, Teng-Fei Chang, Liang He, Shou-Sheng Mao, Ji-Rong Xu, Liang Xiong, Ding-Rong Zhang, Xi-Liang Wang, Jian-Guo Ding, Xu Feng, Hai-Cheng Liu, Xiang-Kun Huang, Yang Chen, Bing-Qiu Yunnan Observatories Chinese Academy of Sciences KunmingYunnan650216 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 Center for Astronomical Mega-Sciences Chinese Academy of Sciences Beijing100012 China South-Western Institute for Astronomy Research Yunnan University Kunming650500 China

We installed two sets of Astronomical Site Monitoring System(ASMS) 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 Mephistro is under construction. ASMS has been running on robotic mode since 2017. The core instruments: Cloud Sensor, All-Sky Camera and Autonomous-DIMM that are developed by our group, together with the commercial Meteorological Station and Sky Quality Meter, are combined into the astronomical optical site monitoring system. The new Cloud Sensor’s Cloud-Clear Relationship is presented for the first time, which is used to calculate the All-Sky cloud cover. We designed the Autonomous-DIMM located on a tower, with the same height as LJT. The seeing data have been observed for a full year. ASMS’s data for the year 2019 are also analysed in detail, which are valuable to observers. Copyright © 2020, The Authors. All rights reserved.

关键词： Observatories

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