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The force-free dipole magnetosphere in non-linear electrodynamics

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arXiv 2019年

作者： Li, Huiquan Yang, Xiaolin 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

Quantum electrodynamics (QED) effects may be included in physical processes of magnetar and pulsar magnetospheres with strong magnetic fields. Involving the quantum corrections, the Maxwell electrodynamics is modified to non-linear electrodynamics. In this work, we study the force-free magnetosphere in non-linear electrodynamics in a general framework. The pulsar equation describing a steady and axisymmetric magnetosphere is derived, which now admits solutions with corrections. We derive the first-order non-linear corrections to the near-zone dipole magnetosphere in some popular non-linear effective theories. The field lines of the corrected dipole tend to converge on the rotational axis so that the fields in the polar region are stronger compared to the pure dipole case. Copyright © 2019, The Authors. All rights reserved.

关键词： Electrodynamics

A flexible method for estimating luminosity functions via Kernel Density Estimation

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arXiv 2020年

作者： Yuan, Zunli Jarvis, Matt J. 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 Astrophysics University of Oxford Denys Wilkinson Building Keble Road OxfordOX1 3RH United Kingdom Physics and Astronomy Department University of the Western Cape Bellville7535 South Africa

We propose a flexible method for estimating luminosity functions (LFs) based on kernel density estimation (KDE), the most popular nonparametric density estimation approach developed in modern statistics, to overcome issues surrounding binning of LFs. One challenge in applying KDE to LFs is how to treat the boundary bias problem, since astronomical surveys usually obtain truncated samples predominantly due to the flux-density limits of surveys. We use two solutions, the transformation KDE method (t), and the transformation-reflection KDE method (tr) to reduce the boundary bias. We develop a new likelihood cross-validation criterion for selecting optimal bandwidths, based on which, the posterior probability distribution of bandwidth and transformation parameters for t and tr are derived within a Markov chain Monte Carlo (MCMC) sampling procedure. The simulation result shows that t and tr perform better than the traditional binned method, especially in the sparse data regime around the flux-limit of a survey or at the bright-end of the LF. To further improve the performance of our KDE methods, we develop the transformation-reflection adaptive KDE approach (tra). Monte Carlo simulations suggest that it has a good stability and reliability in performance, and is around an order of magnitude more accurate than using the binned method. By applying our adaptive KDE method to a quasar sample, we find that it achieves estimates comparable to the rigorous determination in a previous work, while making far fewer assumptions about the LF. The KDE method we develop has the advantages of both parametric and non-parametric methods. Copyright © 2020, The Authors. All rights reserved.

关键词： Surveys

First photometric study of ultrashort-period contact binary 1SWASP J140533.33＋114639.1

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Research in Astronomy and Astrophysics 2018年第3期18卷 57-62页

作者： Bin Zhang Sheng-Bang Qian Ri Michel Boonrucksar Soonthornthum Li-Ying Zhu 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 University of Chinese Academy of Sciences Beijing 100049 China Instituto de Astronomia UNAM Ensenada Mexico National Astronomical Research Institute of Thailand Chiang Mai 50200 Thailand

In this paper,CCD photometric light curves for the short-period eclipsing binary 1 SWASP J140533.33＋114639.1（hereafter J1405） in the BV R bands are presented and analyzed using the 2013 version of the Wilson-Devinney（W-D） code. It is discovered that J1405 is a W-subtype shallow contact binary with a contact degree of f = 7.9±0.5% and a mass ratio of q = 1.55±0.02. In order to explain the asymmetric light curves of the system,a cool starspot on the more massive component is employed. This shallow contact eclipsing binary may have been formed from a short-period detached system through orbital shrinkage due to angular momentum loss. Based on the（O-C） method,the variation of orbital period is studied using all the available times of minimum light. The（O-C） diagram reveals that the period is increasing continuously at a rate of d P/dt = ＋2.09×10^-7 d yr^-1,which can be explained by mass transfer from the less massive component to the more massive one.

关键词： stars binaries close - stars binaries eclipsing - stars individual （1SWASPJ140533.33＋114639.1）

The accretion geometry of the asynchronous polar V1432 aql

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arXiv 2020年

作者： Qishan, Wang Shengbang, Qian Liying, Zhu 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 Yuquan Road 19# Sijingshang Block Beijing100049 China Center for Astronomical Mega-Science Chinese Academy of Science 20A Datun Road Chaoyang Distric Beijing100012 China

As the only eclipsing asynchronous polar (AP), V1432 Aql provides an excellent laboratory to study the interaction between the accreted matter and the magnetic field. However, due to its complex emission, a more physical understanding of its accretion geometry is still outstanding. Here, we report an X-ray spectral study using contemporaneous observations from NuSTAR and Swift. We detect significant Compton reflection and confirm earlier reports of a high soft X-ray temperature ∼ 52 keV. We suggest that the multi-temperature emission is due to a distribution of the specific accretion rate over the accretion region, which leads to a continuous temperature distribution over the heated area and explains the high temperature of the soft X-rays. We interpret these characteristics as the results of the inefficient accretion in APs. Thus the accretion stream can punch deeply into the magnetosphere and feed the white dwarf (WD) over a much narrower accretion region near its equator. Additionally, the broad-band X-rays provide details of the accretion;the low total accretion rate of ∼ 1×10−10 M yr−1 contradicts the speculation that V1432 Aql was a recent nova, while the high specific accretion rate of ∼ 5.6 g cm−2 s−1 explains the significant reflection from the surface of the WD. Copyright © 2020, The Authors. All rights reserved.

关键词： White dwarfs

Black hole magnetospheres in the born-infeld theory

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arXiv 2019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

We study the force-free electrodynamics on rotating black holes in the Born-Infeld (BI) effective theory. The stream equation describing a steady and axisymmetric magnetosphere is derived. From its near-horizon behavior, we obtain the modified Znajek regularity condition, with which we find that the horizon resistivity in the BI theory is generally not a constant. As expected, the outer boundary condition far away from the hole remains unchanged. In terms of the conditions at both boundaries, we derive the perturbative solution of split monopole in the slow rotation limit. It is interesting to realise that the correction to the solution relies not only on the parameter in the BI theory, but also on the radius (or the mass) of the hole. We also show that the quantum effects can undermine the energy extraction process of the magnetosphere in the non-linear theory and the extraction rate gets the maximum in the Maxwell theory. Copyright © 2019, The Authors. All rights reserved.

关键词： Magnetosphere

On the polarized absorption lines in gamma-ray burst optical afterglows

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arXiv 2021年

作者： Mao, J. Britto, R.J. Buckley, D.A.H. Covino, S. D’Avanzo, P. Kuin, N.P.M. Yunnan Observatories Chinese Academy of Sciences Kunming Yunnan Province650011 China Center for Astronomical Mega-Science Chinese Academy of Sciences 20A Datun Road Chaoyang District Beijing100012 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650011 China Department of Physics University of the Free State P.O. Box 339 Bloemfontein9300 South Africa South African Astronomical Observatory P.O. Box 9 Observatory Road Observatory Cape Town7935 South Africa I-23807 Italy Mullard Space Science Laboratory Department of Space and Climate Sciences University College London Holmbury St. Mary DorkingRH5 6NT United Kingdom

Spectropolarimetric measurements of gamma-ray burst (GRB) optical afterglows contain polarization information for both continuum and absorption lines. Based on the Zeeman effect, an absorption line in a strong magnetic field is polarized and split into a triplet. In this paper, we solve the polarization radiative transfer equations of the absorption lines, and obtain the degree of linear polarization of the absorption lines as a function of the optical depth. In order to effectively measure the degree of linear polarization for the absorption lines, a magnetic field strength of at least 103 G is required. The metal elements that produce the polarized absorption lines should be sufficiently abundant and have large oscillation strengths or Einstein absorption coefficients. We encourage both polarization measurements and high-dispersion observations of the absorption lines in order to detect the triplet structure in early GRB optical afterglows. © 2021, CC BY.

关键词： Magnetic fields

A catalogue of potential post common envelope binaries

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arXiv 2021年

作者： Kruckow, Matthias U. Neunteufel, Patrick G. Stefano, Rosanne Di Gao, Yan Kobayashi, Chiaki Yunnan Observatories Chinese Academy of Sciences Kunming650011 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650011 China Max Planck Institut für Astrophysik Karl-Schwarzschild-Straße 1 Garching bei München85748 Germany Harvard-Smithsonian Center for Astrophysics 60 Garden St CambridgeMA02138 United States Institute of Gravitational Wave Astronomy School of Physics and Astronomy University of Birmingham BirminghamB15 2TT United Kingdom Centre for Astrophysics Research School of Physics Astronomy and Mathematics University of Hertfordshire HatfieldAL10 9AB United Kingdom

We present a catalogue containing 839 candidate post common envelope systems. Common envelope evolution is very important in stellar astrophysics, particularly in the context of very compact and short-period binaries, including cataclysmic variables, as progenitors of e.g. supernovae type Ia or mergers of black holes and/or neutron stars. At the same time it is a barely understood process in binary evolution. Due to limitations, since partially remedied, on direct simulation, early investigations were mainly focused on providing analytic prescriptions of the outcome of common envelope evolution. In recent years, detailed hydrodynamical calculations have produced deeper insight into the previously elusive process of envelope ejection. However, a direct link between observations and theory of this relatively short-lived phase in binary evolution has not been forthcoming. Therefore, the main insight to be gained from observations has to be derived from the current state of systems likely to have gone through a common envelope. Here we present an extensive catalogue of such observations as found in the literature. The aim of this paper is to provide a reliable set of data, obtained from observations, to be used in the theoretical modelling of common envelope evolution. In this catalogue, the former common envelope donor star is commonly observed as a white dwarf star or as a hot sub-dwarf star. This catalogue includes period and mass estimates, wherever obtainable. Some binaries are border line cases to allow an investigation of the transition between a common envelope formation and other mass-transfer processes. © 2021, CC BY-NC-ND.

关键词： Mass transfer

Finding Quasars behind the Galactic Plane. II. Spectroscopic Identifications of 204 Quasars at |b|<20°

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arXiv 2022年

作者： Fu, Yuming Wu, Xue-Bing Jiang, Linhua Zhang, Yanxia Huo, Zhi-Ying Ai, Y.L. Yang, Qian Ma, Qinchun Feng, Xiaotong Joshi, Ravi Hon, Wei Jeat Wolf, Christian Li, Jiang-Tao Yao, Su Pang, Yuxuan Wang, Jian-Guo Jin, Jun-Jie Lu, Kai-Xing Wang, Chuan-Jun Zheng, Jie Xu, Liang Yu, Xiao-Guang Lun, Bao-Li Zuo, Pei Department of Astronomy School of Physics Peking University Beijing100871 China Kavli Institute for Astronomy and Astrophysics Peking University Beijing100871 China CAS Key Laboratory of Optical Astronomy National Astronomical Observatories Beijing100101 China National Astronomical Observatories Chinese Academy of Sciences Beijing100101 China College of Engineering Physics Shenzhen Technology University Shenzhen518118 China Shenzhen Key Laboratory of Ultraintense Laser and Advanced Material Technology Shenzhen518118 China Department of Astronomy University of Illinois at Urbana-Champaign UrbanaIL61801 United States School of Physics University of Melbourne ParkvilleVIC3010 Australia Research School of Astronomy and Astrophysics Australian National University CanberraACT2611 Australia Centre for Gravitational Astrophysics Australian National University CanberraACT2600 Australia Department of Astronomy University of Michigan 311 West Hall 1085 S. University Avenue Ann ArborMI48109-1107 United States Purple Mountain Observatory Chinese Academy of Sciences 10 Yuanhua Road Nanjing210023 China Max-Planck-Institut für Radioastronomie Auf dem Hügel 69 BonnD-53121 Germany 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 University of Western Australia 35 Stirling Highway CrawleyWA6009 Australia

Quasars behind the Galactic plane (GPQs) are important astrometric references and valuable probes of Galactic gas, yet the search for GPQs is difficult due to severe extinction and source crowding in the Galactic plan... 详细信息

关键词： Stars

Orbital period correction and light curve modeling of the W-subtype shallow contact binary OW Leo

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arXiv 2020年

作者： Zhou, Xiao Qian, Shengbang 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 Dis-trict Beijing100012 China University of The Chinese Academy of Sciences Yuquan Road 19# Sijingshang Block Beijing100049 China

Orbital period and multi-color light curves' investigation of OW Leo are presented for the first time. The orbital period of OW Leo is corrected from P = 0.325545 days to P = 0.32554052 days in our work, and the observational data from the All-Sky Automated Survey for SuperNovae (ASAS-SN) are used to test the newly determined orbital period. Then, the phased light curves are calculated with the new period and the Wilson-Devinney program is applied to model the light curves, which reveal that OW Leo is a W-subtype shallow contact binary system (q = 3.05, f = 12.8 %). The absolute physical parameters of the two component stars are estimated to be M1 = 0.31(1)M☉, M2 = 0.95(3)M☉, R1 = 0.63(1)R☉, R2 = 1.04(1)R☉, L1 = 0.43(1)L☉ and L2 = 1.01(2)L☉. The evolutionary status show that the more massive star is less evolved than the less massive star. OW Leo has very low metal abundance, which means its formation and evolution are hardly influenced by any additional component. It is formed from an initially detached binary systems through nuclear evolution and angular momentum loss via magnetic braking, and have passed a very long time of main sequence evolution. Copyright © 2020, The Authors. All rights reserved.

关键词： Systems (metallurgical)