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Period studies and photometric models for two EB-type binaries EU Hya and AW Vul

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Research in Astronomy and Astrophysics 2016年第2期16卷 127-134页

作者： Yuan-Gui Yang Qun Li Hua-Li Li Hai-Feng Dai School of Physics and Electronic Information/Information College Huaibei Normal UniversityHuaibei 235000China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of SciencesKunming 650011China National Astronomical Observatories Chinese Academy of SciencesBeijing 100012China

New photometry for two Algol-type binaries, 0.8065 d）, was carried out using the 60-cm telescope EU Hya （P = 0.7782 d） and AW Vul （P = at Xinglong station of National Astronomical Observatories, Chinese Academy of Sciences. With the updated Wilson-Devinney code, photometric el- ements were derived from the multi-color light curves. The modeled results indicate that the two systems are near-contact binaries, whose secondary components fill their Roche lobes. The fill-out factors of the primaries are fp = 81.2 （±0.2）% for EU Hya and fp --- 82.4 （±0.3）% for AW Vul. Period analysis implies that there exists a downward parabola with a light-time orbit from the （O - C） curve. This kind of periodic oscillation may be attributed to the light-time orbit effect of a third companion. The long-term period de- crease may be caused by mass and angular momentum loss. When the orbital period decreases, the fill-out factor of fp will increase. Our results indicate that the primaries will also eventually fill their Roche lobes. EU Hya and AW Vul may possibly evolve from semi-detached binaries into contact ones.

关键词： eclipsing binaries -- stars individual （EU Hya and AW Vul） -- the third companion

A uniformly selected sample of low-mass black holes in seyfert 1 galaxies. II. the sdss dr7 sample

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arXiv 2018年

作者： Liu, He-Yang Yuan, Weimin Dong, Xiao-Bo Zhou, Hongyan Liu, Wen-Juan Key Laboratory of Space Astronomy and Technology National Astronomical Observatories Chinese Academy of Sciences 20A Datun Road Chaoyang District Beijing100012 China School of Astronomy and Space Sciences University of Chinese Academy of Sciences 19A Yuquan Road Beijing100049 China Yunnan Observatories Chinese Academy of Sciences Kunming Yunnan650011 China Key Laboratory for Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming Yunnan650011 China Polar Research Institute of China 451 Jinqiao Road Shanghai200136 China University of Sciences and Technology of China Chinese Academy of Sciences Hefei Anhui230026 China

A new sample of 204 low-mass black holes (LMBHs) in active galactic nuclei (AGNs) is presented with black hole masses in the range of (1-20) × 105 Mo. The AGNs are selected from a systematic search among galaxies in the seventh Data Release (DR 7) of the Sloan Digital Sky Survey (SDSS), by careful analyses of their optical spectra and precise measurement of spectral parameters. Combining them with our previous sample selected from the SDSS DR 4 makes it the largest LMBH sample so far, totaling over 500 objects. Some of the statistical properties of the combined LMBH AGN sample are briefly discussed, in the context of exploring the low-mass end of the AGN population. Their X-ray luminosities follow the extension of the previously known correlation with the [O III] luminosity. The effective optical-to-X-ray spectral indices αOX, albeit with a large scatter, are broadly consistent with the extension of the relation with the near-UV luminosity L2500Å. Interestingly, a correlation of αOX with black hole mass is also found in the sense that αOX is statistically flatter (stronger X-ray relative to optical) for lower black hole mass. Only 26 objects, mostly radio loud, were detected in radio at 20 cm in the FIRST survey, giving a radio loud fraction of 4%. The host galaxies of LMBHs have stellar masses in the range of 108.8-1012.4 Mo and optical colors typical of Sbc spirals. They are dominated by young stellar populations which seem to have undergone a continuous star formation history. Copyright © 2018, The Authors. All rights reserved.

关键词： Stars

Accreting He-rich material onto carbon-oxygen white dwarfs until explosive carbon ignition

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Research in Astronomy and Astrophysics 2016年第10期16卷 93-98页

作者： Cheng-YuanWu Dong-Dong Liu Wei-Hong Zhou Bo Wang Yunnan Observatories Chinese Academy of SciencesKunming 650216China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of SciencesKunming 650216China University of Chinese Academy of Sciences Beiiing 100049China Yunnan Minzu University Kunming 650031China

Type Ia supernovae （SNe Ia） play an important role in studies of cosmology and galactic chemi- cal evolution. They are believed to be thermonuclear explosions of carbon-oxygen white dwarfs （CO WDs） when their masses approach the Chandrasekar （Ch） mass limit. However, it is still not completely under- stood how a CO WD increases its mass to the Ch-mass limit in the classical single-degenerate （SD） model. In this paper, we studied the mass accretion process in the SD model to examine whether the WD can explode as an SN Ia. Employing the stellar evolution code called modules for experiments in stellar as- trophysics （MESA）, we simulated the He accretion process onto CO WDs. We found that the WD can increase its mass to the Ch-mass limit through the SD model and explosive carbon ignition finally occurs in its center, which will lead to an SN Ia explosion. Our results imply that SNe Ia can be produced from the SD model through steady helium accretion. Moreover, this work can provide initial input parameters for explosion models of SNe Ia.

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

Precise determination of stellar parameters of the ZZ Ceti and DAZ white dwarf GD 133 through asteroseismology

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arXiv 2019年

作者： Fu, J.-N. Vauclair, G. Su, J. Machado, L. Fox Colas, F. Kim, S.-L. Cang, T.Q. Li, C. Niu, H.B. Xue, H.F. Li, Y. Jiang, X.-J. Michel, R. Alvarez, M. Dolez, N. Ma, L. Esamdin, A. Liu, J.Z. Department of Astronomy Beijing Normal University Beijing100875 China Université de Toulouse UPS-OMP IRAP Toulouse France CNRS IRAP 14 av. Edouard Belin ToulouseF-31400 France Yunnan Observatories Chinese Academy of Sciences P.O. Box 110 Kunming650216 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences P.O. Box 110 Kunming650216 China Instituto de Astronomía Observatorio Astronómico Nacional San Pedro Mártir Universidad Nacional Autónoma de México Ensenada Baja california22860 Mexico IMCCE Observatoire de Paris UMR 8028 CNRS ParisF-75014 France Korea Astronomy and Space Science Institute Daejeon34055 Korea Republic of National Astrononomical Observatories Chinese Academy of Sciences 20A Datun Road Chaoyang District Beijing100012 China Xinjiang Astronomical Observatory Chinese Academy of Sciences Urumqi830011 China

An increasing number of white dwarf stars show atmospheric chemical composition polluted by heavy elements accreted from debris disk material. The existence of such debris disks strongly suggests the presence of one or more planet(s) whose gravitational interaction with rocky planetesimals is responsible for their disruption by tidal effect. The ZZ Ceti pulsator and polluted DAZ white dwarf GD 133 is a good candidate for searching for such a potential planet. We started in 2011 a photometric follow-up of its pulsations. As a result of this work in progress, we used the data gathered from 2011 to 2015 to make an asteroseismological analysis of GD 133, providing the star parameters from a best fit model with M/Mo= 0.630 ±0.002, Teff= 12400 K ±70K, log(MHe/M)= -2.00 ±0.02, log(MH/M)= -4.50 ±0.02 and determining a rotation period of ≈ 7 days. Copyright © 2019, The Authors. All rights reserved.

关键词： White dwarfs

Expanded solutions of force-free electrodynamics on general Kerr black holes

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arXiv 2017年

作者： Li, Huiquan Wang, Jiancheng 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

In this work, expanded solutions of force-free magnetospheres on general Kerr black holes are derived through a radial distance expansion method. From the regular conditions both at the horizon and at spatial infinity, two previously known asymptotical solutions (one of them is actually an exact solution) are identified as the only solutions that satisfy the same conditions at the two boundaries. Taking them as initial conditions at the boundaries, expanded solutions up to the first few orders are derived by solving the stream equation order by order. It is shown that our extension of the exact solution can (partially) cure the problems of the solution: it leads to magnetic domination and a mostly timelike current for restricted parameters. Copyright © 2017, The Authors. All rights reserved.

关键词： Magnetosphere

MULTI-WAVELENGTH OBSERVATIONS OF A NEW REDBACK MILLISECOND PULSAR CANDIDATE: 3FGL J0954.8−3948

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arXiv 2018年

作者： Li, Kwan-Lok Hou, Xian Strader, Jay Takata, Jumpei Kong, Albert K.H. Chomiuk, Laura Swihart, Samuel J. Hui, Chung Yue Cheng, K.S. Department of Physics and Astronomy Michigan State University East LansingMI48824 United States Yunnan Observatories Chinese Academy of Sciences Kunming650216 China Key laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650216 China School of physics Huazhong University of Science and Technology Wuhan430074 China Institute of Astronomy National Tsing Hua University Hsinchu30013 Taiwan Department of Astronomy and Space Science Chungnam National University Daejeon34134 Korea Republic of Department of Physics University of Hong Kong Pokfulam Road Hong Kong

We present a multi-wavelength study of the unassociated Fermi-LAT source, 3FGL J0954.8−3948, which is likely the γ-ray counterpart of a 9.3-hour binary in the field. With more than 9 years of Pass 8 LAT data, we updated the γ-ray spectral properties and the LAT localization of the γ-ray source. While the binary lies outside the cataloged 95% error ellipse, the optimized LAT ellipse is 0.1 degrees closer and encloses the binary. The system is likely spectrally hard in X-rays (photon index ΓX = 1.4−+11..20) with orbital modulations detected in optical, UV, and possibly X-rays. A steep spectrum radio counterpart (spectral index α ≈ −1.6) is also found in the TIFR GMRT Sky Survey (TGSS), implying that it is a pulsar system. We obtained a series of SOAR and Gemini spectroscopic observations in 2017/2018, which show a low-mass secondary orbiting in a close circular orbit with K2 = 272 ± 4 km s−1 under strong irradiation by the primary compact object. All the observations as well as the modelling of the X/γ-ray high-energy emission suggest that 3FGL J0954.8−3948 is a redback millisecond pulsar in a rotation-powered state. Copyright © 2018, The Authors. All rights reserved.

关键词： Pulsars

Chemical properties of two dense cores in a planck galactic cold clump G168.72-15.48

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arXiv 2019年

作者： Tang, Mengyao Ge, J.X. Qin, Sheng-Li Liu, Tie Wu, Yuefang Kim, Kee-Tae Liu, Sheng-Yuan Zhang, Chao He, J.H. Ju, Bing-Gang Fang, Xinhe Department of Astronomy Yunnan University Key Laboratory of Astroparticle Physics of Yunnan Province Kunming650091 China Departamento de Astronomía Universidad de Chile Camino el Observatorio 1515 Las Condes Santiago Chile Shanghai Astronomical Observatory Chinese Academy of Sciences 80 Nandan Road Shanghai200030 China Department of Astronomy Peking University Beijing100871 China Korea Astronomy and Space Science Institute 776 Daedeokdaero Yuseong-gu Daejeon34055 Korea Republic of University of Science and Technology 217 Gajeong-ro Yuseong-gu Daejeon34113 Korea Republic of Institute of Astronomy and Astrophysics Academia Sinica 11F of Astronomy-Mathematics Building AS/NTU No. 1 Taipei10617 Taiwan Key Laboratory for the Structure and Evolution of Celestial Objects Yunnan Observatories Chinese Academy of Sciences P.O. Box 110 Kunming Yunnan Province650011 China Camino El Observatorio 1515 Las Condes Santiago Chile Departamento de Astronomía Universidad de Chile Las Condes Santiago Chile Purple Mountain Observatory Qinghai Station Delingha817000 China Department of Electronic Engineering Zhengzhou Railway Vocational & Technical College Zhengzhou451460 China

To deepen our understanding of the chemical properties of the Planck Galactic Cold Clump (PGCC) G168.72-15.48, we performed observations of nine molecular species, namely, c-C3H, H2CO, HC5N, HC7N, SO, CCH, N2H+, CH3OH, and CH3CCH, toward two dense cores in PGCC G168.72-15.48 using the Tianma Radio Telescope and Purple Mountain Observatory Telescope. We detected c-C3H, H2CO, HC5N, N2H+, CCH, and CH3OH in both G168-H1 and G168-H2 cores, whereas HC7N and CH3CCH were detected only in G168-H1 and SO was detected only in G168-H2. Mapping observations reveal that the CCH, N2H+, CH3OH, and CH3CCH emissions are well coupled with the dust emission in G168-H1. Additionally, N2H+exhibits an exceptionally weak emission in the denser and more evolved G168-H2 core, which may be attributed to the N2H+depletion. We suggest that the N2H+depletion in G168-H2 is dominated by N2depletion, rather than the destruction by CO. The local thermodynamic equilibrium calculations indicate that the carbon-chain molecules of CCH, HC5N, HC7N, and CH3CCH are more abundant in the younger G168-H1 core. We found that starless core G168-H1 may have the properties of cold dark clouds based on its abundances of carbon-chain molecules. While, the prestellar core G168-H2 exhibits lower carbon-chain molecular abundances than the general cold dark clouds. With our gas-grain astrochemical model calculations, we attribute the observed chemical differences between G168-H1 and G168-H2 to their different gas densities and different evolutionary stages. Copyright © 2019, The Authors. All rights reserved.

关键词： Molecules

ALMA [N ii ] 205 µm Imaging Spectroscopy of the Lensed Submillimeter galaxy ID 141 at redshift 4.24

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arXiv 2020年

作者： Cheng, Cheng Cao, Xiaoyue Lu, Nanyao Li, Ran Yang, Chentao Rigopoulou, Dimitra Charmandaris, Vassilis Gao, Yu Xu, Cong Kevin van der Werf, Paul Santos, Tanio Diaz Privon, George C. Zhao, Yinghe Cao, Tianwen Dai, Y. Sophia Huang, Jia-Sheng Sanders, David Wang, Chunxiang Wang, Zhong Zhu, Lei National Astronomical Observatories Chinese Academy of Sciences 20A Datun Road Chaoyang District Beijing100101 China China-Chile Joint Center for Astronomy Camino El Observatorio 1515 Las Condes Santiago Chile Instituto de Física y Astronomía Universidad de Valparaíso Avda. Gran Bretaña 1111 Valparaíso Chile 20A Datun Road Chaoyang District Beijing100012 China School of Astronomy and Space Science University of Chinese Academy of Science 19 A Yuquan Rd Shijingshan District Beijing100049 China European Southern Observatory Alonso de CÃşrdova 3107 Casilla 19001 Vitacura Santiago Chile Astrophysics Department University of Oxford OxfordOX1 3RH United Kingdom Department of Physics University of Crete HeraklionGR-71003 Greece Institute of Astrophysics FORTH HeraklionGR-71110 Greece Department of Astronomy Xiamen University XiamenFujian361005 China Nanjing210033 China Leiden Observatory Leiden University P.O. Box 9513 Leiden2300 RA Netherlands Nucleo de Astronomia de la Facultad de Ingenieria Universidad Diego Portales Av. Ejercito Libertador 441 Santiago Chile Department of Astronomy University of Florida 211 Bryant Space Sciences Center GainesvilleFL32611 United States Yunnan Observatories Chinese Academy of Sciences Kun-ming650011 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650011 China Center for Astronomical Mega-Science CAS 20A Datun Road Chaoyang District Beijing100012 China Institute for Astronomy University of Hawaii 2680 Woodlawn Drive HonoluluHI96822 United States

We present the Atacama Large Millimeter/submillimeter Array (ALMA) observation of the Submillimeter galaxy (SMG) ID 141 at z=4.24 in the [N ii ] 205 µm line (hereafter [N ii ]) and the underlying continuum at (rest-frame) 197.6 µm. Benefiting from lensing magnification by a galaxy pair at z=0.595, ID 141 is one of the brightest z > 4 SMGs. At the angular resolutions of ∼ 1.2″ to 1.5″ (1″∼6.9 kpc), our observation clearly separates, and moderately resolves the two lensed images in both continuum and line emission at S/N > 5 . Our continuum-based lensing model implies an averaged amplification factor of ∼ 5.8 and reveals that the de-lensed continuum image has the Sérsic index'0.95 and the Sérsic radius of ∼0.1800 (∼1.24 kpc). Furthermore, the reconstructed [N ii ] velocity field in the source plane is dominated by a rotation component with a maximum velocity of ∼300 km/s at large radii, indicating a dark matter halo mass of ∼1012M. This, together with the reconstructed velocity dispersion field being smooth and modest in value ( Copyright © 2020, The Authors. All rights reserved.

关键词： Galaxies

He-accreting carbon-oxygen white dwarfs and type Ia supernovae

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arXiv 2017年

作者： Wang, Bo Podsiadlowski, Philipp Han, Zhanwen Key Laboratory for the Structure and Evolution of Celestial Objects Yunnan Observatories CAS Kunming650216 China Center for Astronomical Mega-Science CAS Beijing100012 China Department of Astronomy Oxford University OxfordOX1 3RH United Kingdom

He accretion onto carbon-oxygen white dwarfs (COWDs) plays a fundamental role when studying the formation of type Ia supernovae (SNe Ia). Employing the MESA stellar evolution code, we calculated the long-term evolution of He-accreting CO WDs. Previous studies usually supposed that a WD can grow in mass to the Chandrasekhar limit in the stable He burning region and finally produce a SN Ia. However, in this study we find that off-centre carbon ignition occurs in the stable He burning region if the accretion rate is above a critical value (∼2.05 × 10-6Moyr-1), resulting in accretion-induced collapse rather than a SN Ia. If the accretion rate is below the critical value, explosive carbon ignition will eventually happen in the centre producing a SN Ia. Taking into account the possibility of off-centre carbon ignition, we have re-determined the initial parameter space that produces SNe Ia in the He star donor channel, one of the promising channels to produce SNe Ia in young populations. Since this parameter space is smaller than was found in the previous study ofWang et al. (2009), the SN Ia rates are also correspondingly smaller. We also determined the chemical abundance profile of the He-accreting WDs at the moment of explosive carbon ignition, which can be used as initial input for SN Ia explosion models. Copyright © 2017, The Authors. All rights reserved.

关键词： White dwarfs