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arXiv 2020年

作者： Wu, Chengyuan Wang, Bo. Wang, Xiaofeng Maeda, Keiichi Mazzali, Paolo Tsinghua University Beijing100084 China Key Laboratory for the Structure and Evolution of Celestial Objects Yunnan Observatories CAS Kunming650216 China Department of Astronomy Kyoto University Kitashirakawa-Oiwake-cho Sakyo-ku Kyoto606-8502 Japan Astrophysics Research Institute Liverpool John Moores University IC2 Liverpool Science Park 146 Brownlow Hill LiverpoolL3 5RF United Kingdom

The carbon-oxygen white dwarf (CO WD) + He star channel has been thought to be one of the promising scnarios to produce young type Ia supernovae (SNe Ia). Previous studies found that if the mass-accretion rate is greater than a critical value, the He-accreting CO WD will undergo inwardly propagating (off-centre) carbon ignition when it increases its mass close to the Chandrasekhar limit. The inwardly propagating carbon flame was supposed to reach the centre by previous works, leading to the production of an oxygen-neon (ONe) WD that may collapse into a neutron star but not an SN Ia. However, it is still uncertain how the carbon flame propagates under the effect of mixing mechanisms. In the present work, we aim to investigate the off-centre carbon burning of the He-accreting CO WDs by considering the effect of convective mixing. We found that the temperature of the flame is high enough to burn the carbon into silicon-group elements in the outer part of the CO core even if the convective overshooting is considered, but the flame would quench somewhere inside the WD, resulting in the formation of a C-O-Si WD. Owing to the inefficiency of thermohaline mixing, the C-O-Si WD may explode as an SN Ia if it continues to grow in mass. Our radiation transfer simulations show that the SN ejecta with the silicon-rich outer layer will form high-velocity absorption lines in Si II, leading to some similarities to a class of the high-velocity SNe Ia in the spectral evolution. We estimate that the birthrate of SNe Ia with Si-rich envelope is ∼1 × 10−4 yr−1 in our galaxy. Copyright © 2020, The Authors. All rights reserved.

关键词： White dwarfs

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A flexible method for estimating luminosity functions via Kernel Density Estimation

arXiv

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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

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The black hole spin in coalescing binary black holes and high-mass X-ray binaries

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Proceedings of the International Astronomical Union 2019年第S346期14卷 426-432页

作者： Qin, Y. Fragos, T. Meynet, G. Marchant, P. Kalogera, V. Andrews, J. Sørensen, M. Song, H.F. Geneva Observatory University of Geneva Switzerland Center for Interdisciplinary Exploration and Research in Astrophysics Department of Physics and Astrophysics Northwestern University Evanston 60208 IL United States Foundation for Research and Technology-Hellas IESL Voutes Heraklion 71110 Greece Physics Department Institute of Theoretical and Computational Physics University of Crete Heraklion Crete 71003 Greece College of Physics Guizhou University Guiyang City Guizhou Province 550025 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming 650011 China

The six LIGO detections of merging black holes (BHs) allowed to infer slow spin values for the two pre-merging BHs. The three cases where the spins of the BHs can be determined in high-mass X-ray binaries (HMXBs) show that those BHs have high spin values. We discuss here scenarios explaining these differences in spin properties in these two classes of object. © International Astronomical Union 2019.

关键词： Binaries: Close binary stars black hole gravitational waves X-rays: Binaries

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The force-free dipole magnetosphere in non-linear electrodynamics

arXiv

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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

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SCATTER: A New Common Envelope Formalism

arXiv

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arXiv 2022年

作者： Di Stefano, Rosanne Kruckow, Matthias U. Gao, Yan Neunteufel, Patrick G. Kobayashi, Chiaki Harvard-Smithsonian Center for Astrophysics 60 Garden St CambridgeMA02138 United States Yunnan Observatories Chinese Academy of Sciences Kunming650011 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650011 China Département d’Astronomie Université de Genève Chemin Pegasi 51 VersoixCH-1290 Switzerland Université de Genève GenevaCH-1211 Switzerland University of Chinese Academy of Sciences China Institute of Gravitational Wave Astronomy School of Physics and Astronomy University of Birmingham BirminghamB15 2TT United Kingdom Max Planck Institut für Astrophysik Karl-Schwarzschild-Straße 1 Garching bei München85748 Germany Centre for Astrophysics Research Department of Physics Astronomy and Mathematics University of Hertfordshire HatfieldAL10 9AB United Kingdom

One of the most mysterious astrophysical states is the common envelope (CE) phase of binary evolution, in which two stars are enshrouded by the envelope shed by one of them. Interactions between the stars and the envelope shrinks the orbit. The CE can lead to mergers or to a subsequent phase of interactions. Mergers may involve any combination of two compact objects and/or stars. Some involving white dwarfs, may produce Type Ia supernovae, while merging neutron stars may yield gamma-ray bursts, and merging compact objects of all kinds produce gravitational radiation. Since CEs can arise from a variety of different initial conditions, and due to the complexity of the processes involved, it is difficult to predict their end states. When many systems are being considered, as in population synthesis calculations, conservation principles are generally employed. Here we use angular momentum in a new way to derive a simple expression for the final orbital separation. This method provides advantages for the study of binaries and is particularly well-suited to higher order multiples, now considered to be important in the genesis of potential mergers. Here we focus on CEs in binaries, and the follow-up paper extends our formalism to multiple star systems within which a CE occurs. © 2022, CC0.

关键词： Merging

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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）

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The accretion geometry of the asynchronous polar V1432 aql

arXiv

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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

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Blue large-amplitude pulsators: The possible surviving companions of type ia supernovae

arXiv

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arXiv 2020年

作者： Meng, Xiang-Cun Han, Zhan-Wen Podsiadlowski, Philipp Li, Jiao 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 20A Datun Road Chaoyang District Beijing100012 China Department of Astronomy Oxford University OxfordOX1 3RH United Kingdom Key Laboratory of Space Astronomy and Technology National Astronomical Observatories Chinese Academy of Sciences Beijing100101 China

The single degenerate (SD) model, one of the leading models for the progenitors of Type Ia supernovae (SNe Ia), predicts that there should be binary companions that survive the supernova explosion which, in principle, should be detectable in the Galaxy. The discovery of such surviving companions could therefore provide conclusive support for the SD model. Several years ago, a new type of mysterious variables was discovered, the so-called blue large-amplitude pulsators (BLAPs). Here we show that all the properties of BLAPs can be reasonably well reproduced if they are indeed such surviving companions, in contrast to other proposed channels. This suggests that BLAPs could potentially be the long-sought surviving companions of SNe Ia. Our model also predicts a new channel for forming single hot subdwarf stars, consistent with a small group in the present hot-subdwarf-star sample. Copyright © 2020, The Authors. All rights reserved.

关键词： White dwarfs

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

arXiv

引用

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)

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Black hole magnetospheres in the born-infeld theory

arXiv

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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

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