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arXiv 2020年

作者： Zheng, Y.G. Yang, C.Y. Kang, Shi-Ju Bai, J.M. Yunnan Observatories Chinese Academy of Sciences Kunming650011 China Department of Physics Yunnan Normal University Kunming650092 China Shandong Provincial Key Laboratory of Optical Astronomy and Solar-Terrestrial Environment-Shandong University Weihai264209 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences China Department of Physics and Electronics Science Liupanshui Normal University LiupanshuiGuizhou553004 China

It is surprising to find a fact for migration in the peak positions of synchrotron spectra energy distribution component during in the activity epochs of Mrk 421, accompanying with an orphan flaring at the X-ray and GeV-TeV γ-ray bands. A geometric interpretation and standard shock or stochastic acceleration models of blazar emission have difficulty reproducing these observed behaviours. The present paper introduces a linear acceleration by integrating the reconnection electric field into the particle transport model for the observed behaviours of Mrk 421. We note that the strong evidence for evolution of multi-wavelength spectral energy distribution characteristic by shifting the peak frequency, accompanying with an orphan flaring at the X-ray and GeV-TeV γ-ray bands provides an important electrostatic acceleration diagnostic in blazar jet. Assuming suitable model parameters, we apply the results of the simulation to the 13-day flaring event in 2010 March of Mrk 421, concentrating on the evolution of multi-wavelength spectral energy distribution characteristic by shifting the peak frequency. It is clear that the ratio of the electric field and magnetic field strength plays an important role in temporal evolution of the peak frequency of synchrotron spectral energy distribution component. We suggest the electrostatic acceleration responsible for the evolution of multi-wavelength spectral energy distribution characteristic by shifting the peak frequency is reasonable. Based on the model results, we issue that the peak frequency of the synchrotron spectral energy distribution component may denote a temporary characteristic of blazars, rather than a permanent one. Copyright © 2020, The Authors. All rights reserved.

关键词： Spectroscopy

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Morpho-Photometric Classification of KiDS DR5 Sources Based on Neural Networks: A Comprehensive Star-Quasar-Galaxy Catalog

arXiv

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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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The new compact triple system: discovery of bright third star around contact binary using LAMOST-MRS spectra and photometry.

arXiv

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arXiv 2025年

作者： Kovalev, Mikhail Matekov, Azizbek Guo, Sufen Chen, Xuefei Han, Zhanwen Yunnan Observatories China Academy of Sciences Kunming650216 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650011 China International Centre of Supernovae Yunnan Key Laboratory Kunming650216 China University of Chinese Academy of Sciences Yuquan Road 19 Sijingshang Block Beijing100049 China Ulugh Beg Astronomical Institute Uzbekistan Academy of Sciences 33 Astronomicheskaya str. Tashkent100052 Uzbekistan School of Physical Science and Technology Xinjiang University Urumqi830046 China Center for Astronomical Mega-Science Chinese Academy of Sciences 20A Datun Road Chaoyang District Beijing100012 China

We present a study of the third star orbiting around known contact eclipsing binary J04+25 using spectra from the LAMOST medium-resolution survey (MRS) and publicly available photometry. This is a rare case of a hierarchical triple, where the third star is significantly brighter than the inner contact subsystem. We successfully extracted radial velocities for all three components, using the binary spectral model in two steps. Third star radial velocities have high precision and allow direct fitting of the orbit. The low precision of radial velocity measurements in the contact system is compensated by large number *** employed a template matching technique for light curves to find periodic variation due to the light time travel effect (LTTE) using several photometric datasets. Joint fit of third star radial velocities and LTTE allowed us to get a consistent orbital solution with P3 = 941.40 ± 0.03 day and e3 = 0.059 ± 0.007. We made estimations of the masses M12, 3 sin3 i3 = 1.05 ± 0.02, 0.90 ± 0.02 M☉ in a wide system and discussed possible determination of an astrometric orbit in the future data release of Gaia. Additionally, we propose an empirical method for measuring a period and minimal mass of contact systems, based on variation of the projected rotational velocity (V sin i) from the spectra. Copyright © 2025, The Authors. All rights reserved.

关键词： Template matching

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Detection of Semidetached Eclipsing Binaries from TESS

arXiv

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arXiv 2025年

作者： Ding, Xu Ji, KaiFan Cheng, QiYuan Song, ZhiMing Wang, JinLiang Tian, XueFen Wang, ChuanJun 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 University of the Chinese Academy of Sciences Yuquan Road 19# Shijingshan Block Beijing100049 China School of Information Yunnan University of Finance and Economics Kunming China Yunnan Key Laboratory of Service Computing Kunming China Communication And Information Engneering College Yunnan Open University Kunming650500 China

Semi-detached binaries, distinguished by their mass transfer phase, play a crucial role in elucidating the physics of mass transfer within interacting binary systems. To identify these systems in Eclipsing binary (EB) light curves provided by large-scale time-domain surveys, we have developed a methodology by training two distinct models that establish a mapping relationship between the parameters (orbital parameters and physical parameters) of semi-detached binaries and their corresponding light curves. The first model corresponds to scenarios where the more massive star fills its Roche lobe, while the second model addresses situations where the less massive star does so. In consideration of the O’Connell effect observed in the light curves, we integrated a cool spot parameter into our models, thereby enhancing their applicability to fit light curves that exhibit this phenomenon. Our two-model framework was then harmonized with the Markov Chain Monte Carlo (MCMC) algorithm, enabling precise and efficient light curve fitting and parameter estimation. Leveraging 2-minute cadence data from the initial 67 sectors of TESS, we successfully identified 327 systems where the less massive component fills its Roche lobe, alongside 3 systems where the more massive component fills its Roche lobe. Additionally, we offer comprehensive fundamental parameters for these binary systems, including orbital inclination, relative radius, mass ratio, and effective temperature. Copyright © 2025, The Authors. All rights reserved.

关键词： Monte Carlo methods

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He-shell flashes on the surface of oxygen-neon white dwarfs

arXiv

引用

arXiv 2020年

作者： Guo, Yunlang Liu, Dongdong Wu, Chengyuan Wang, Bo 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 Tsinghua University Beijing100084 China

Accretion induced collapse (AIC) may be responsible for the formation of some interesting neutron star binaries, e.g., millisecond pulsars, intermediate-mass binary pulsars, etc. It has been suggested that oxygen-neon white dwarfs (ONe WDs) can increase their mass to the Chandrasekhar limit by multiple He-shell flashes, leading to AIC events. However, the properties of He-shell flashes on the surface of ONe WDs are still not well understood. In this article, we aim to study He-shell flashes on the surface of ONe WDs in a systematic approach. We investigated the long-term evolution of ONe WDs accreting He-rich material with various constant mass-accretion rates by time-dependent calculations with the stellar evolution code Modules for Experiments in Stellar Astrophysics (MESA), in which the initial ONe WD masses range from 1.1 to 1.35 M☉. We found that the mass-retention efficiency increases with the ONe WD mass and the mass-accretion rate, whereas both the nova cycle duration and the ignition mass decrease with the ONe WD mass and the mass-accretion rate. We also present the nuclear products in different accretion scenarios. The results presented in this article can be used in the future binary population synthesis studies of AIC events. Copyright © 2020, The Authors. All rights reserved.

关键词： White dwarfs

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A highly mutually-inclined, compact warm-Jupiter system KOI-984 ?

arXiv

引用

arXiv 2021年

作者： Sun, Leilei Ioannidis, Panagiotis Gu, Shenghong Schmitt, Jürgen H.M.M. Wang, Xiaobin Kouwenhoven, M.B.N. Perdelwitz, Volker Dotti, Francesco Flammini Czesla, Stefan Yunnan Observatories Chinese Academy of Sciences Kunming650216 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650216 China Hamburger Sternwarte Universität Hamburg Gojenbergsweg 112 Hamburg21029 Germany School of Astronomy and Space Science University of Chinese Academy of Sciences Beijing101408 China 111 Renai Rd. Suzhou Dushu Lake Science and Education Innovation District Suzhou Industrial Park Suzhou215123 China Department of Physics Ariel University Ariel40700 Israel

The discovery of a population of close-orbiting giant planets (≤ 1 au) has raised a number of questions about their origins and dynamical histories. These issues have still not yet been fully resolved, despite over 20 years of exoplanet detections and a large number of discovered exoplanets. In particular, it is unclear whether warm Jupiters (WJs) form in situ, or whether they migrate from further outside and are even currently migrating to form hot Jupiters (HJs). Here, we report the possible discovery and characterization of the planets in a highly mutually-inclined (Imut 45◦), compact two-planet system (KOI-984), in which the newly discovered warm Jupiter KOI-984c is on a 21.5-day, moderately eccentric (e 0.4) orbit, in addition to a previously known 4.3-day planet candidate KOI-984b. Meanwhile, the orbital configuration of a moderately inclined (Imut 15◦), low-mass (mc 24M⊕;Pb 8.6 days) perturbing planet near 1:2 mean motion resonace with KOI-984b could also well reproduce observed transit timing variations and transit duration variations of KOI-984b. Such an eccentric WJ with a close-in sibling would pose a challenge to the proposed formation and migration mechanisms of WJs, if the first scenario is supported with more evidences in near future;this system with several other well-measured inclined WJ systems (e.g., Kepler-419 and Kepler-108) may provide additional clues for the origin and dynamical histories of WJs. Copyright © 2021, The Authors. All rights reserved.

关键词： Extrasolar planets

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Mass-accreting white dwarfs and type Ia supernovae

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Research in Astronomy and Astrophysics 2018年第5期18卷 1-28页

作者： Bo Wang Key Laboratory for the Structure and Evolution of Celestial Objects Yunnan Observatories Chinese Academy ofSciences Kunming 650216 China Center for Astronomical Mega-Science Chinese Academy of Sciences Beijing 100101 China University of Chinese Academy of Sciences Beijing 100049 China

Type Ia supernovae（SNe Ia） play a prominent role in understanding the evolution of the Universe. They are thought to be thermonuclear explosions of mass-accreting carbon-oxygen white dwarfs（CO WDs） in binaries, although the mass donors of the accreting WDs are still not well determined. In this article, I review recent studies on mass-accreting WDs, including H-and He-accreting WDs. I also review currently most studied progenitor models of SNe Ia, i.e., the single-degenerate model（including the WD＋MS channel, the WD＋RG channel and the WD＋He star channel）, the doubledegenerate model（including the violent merger scenario） and the sub-Chandrasekhar mass *** progress on these progenitor models is discussed, including the initial parameter space for producing SNe Ia, the binary evolutionary paths to SNe Ia, the progenitor candidates for SNe Ia, the possible surviving companion stars of SNe Ia, some observational constraints, etc. Some other potential progenitor models of SNe Ia are also summarized, including the hybrid CONe WD model, the core-degenerate model, the double WD collision model, the spin-up/spin-down model and the model of WDs near black holes. To date, it seems that two or more progenitor models are needed to explain the observed diversity among SNe Ia.

关键词： supernovae general - binaries close - stars evolution - 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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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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Formation of millisecond pulsars with helium white dwarfs, ultra-compact X-ray binaries and gravitational wave sources

arXiv

引用

arXiv 2021年

作者： Chen, Hai-Liang Tauris, Thomas M. Han, Zhanwen Chen, Xuefei Kunming650216 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650011 China Department of Physics and Astronomy Aarhus University Ny Munkegade 120 Aarhus C8000 Denmark Aarhus University Høegh-Guldbergs Gade 6B Aarhus C8000 Denmark University of the Chinese Academy of Sciences Yuquan Road 19 Shijingshan Block Beijing100049 China Center for Astronomical Mega-Science Chinese Academy of Sciences 20A Datun Road Chaoyang District Bejing100012 China

Close-orbit low-mass X-ray binaries (LMXBs), radio binary millisecond pulsars (BMSPs) with extremely low-mass helium WDs (ELM He WDs) and ultra-compact X-ray binaries (UCXBs) are all part of the same evolutionary sequence. It is therefore of uttermost importance to understand how these populations evolve from one specie to another. Moreover, UCXBs are important gravitational wave (GW) sources and can be detected by future space-borne GW observatories. However, the formation and evolutionary link between these three different populations of neutron star (NS) binaries are not fully understood. In particular, a peculiar fine-tuning problem has previously been demonstrated for the formation of these systems. In this investigation, we test a newly suggested magnetic braking prescription and model the formation and evolution of LMXBs. We compute a grid of binary evolution models and present the initial parameter space of the progenitor binaries which successfully evolve all the way to produce UCXBs. We find that the initial orbital period range of LMXBs, which evolve into detached NS+ELM He WD binaries and later UCXBs, becomes significantly wider compared to evolution with a standard magnetic braking prescription, and thus helps to relieve the fine-tuning problem. However, we also find that formation of wide-orbit BMSPs is prohibited for strong versions of this new magnetic braking prescription, which therefore calls for a revision of the prescription. Finally, we present examples of the properties of UCXBs as Galactic GW sources and discuss their detection by the LISA, TianQin and Taiji observatories. © 2021, CC BY-NC-SA.

关键词： Gravity waves

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