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Helium Star Donor Channel to Type Ia Supernovae and Their Surviving Companion Stars

Proceedings of the International Astronomical Union 2013年第S281期7卷 205-208页

作者： Bo Wang Zhanwen Han National Astronomical Observatories/Yunnan Observatory CAS Kunming 650011 China (email: wangbo@***) Key Laboratory for the Structure and Evolution of Celestial Objects CAS Kunming 650011 China

Employing Eggleton's stellar evolution code and assuming optically thick winds, we systematically studied the He star donor channel of Type Ia supernovae (SNe Ia), in which a carbon-oxygen white dwarf (WD) accretes material from a He main-sequence star or a He subgiant to increase its mass to the Chandrasekhar mass. We mapped out the initial parameters for producing SNe Ia in the orbital period–secondary mass plane for various WD masses from this channel. Based on a detailed binary population synthesis approach, we find that this channel can produce SNe Ia with short delay times (~100 Myr) implied by recent observations. We derived many properties of the surviving companions of this channel after SN explosion, which can be tested by future observations. We also find that the surviving companions from the SN explosion scenario have a high spatial velocity (>400 km/s), which could be an alternative origin for hypervelocity stars (HVSs), especially for HVSs such as US 708.

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

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ON GRB PHYSICS REVEALED BY FERMI/LAT

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International Journal of Modern Physics: Conference Series 2013年第23期ijmpcs卷 223-227页

作者： ZHUO LI Department of Astronomy/Kavli Institute for Astronomy and Astrophysics Peking University Beijing 100871 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming 650011 China

We discuss the implications of Fermi/LAT observations on several aspects of gamma-ray burst (GRB) physics, including the radiation process, the emission sites, the bulk Lorentz factor, and the pre-shock magnetic field: (1) MeV-range emission favors synchrotron process but the highest energy (> 10 GeV) emission may not be synchrotron origin, more likely inverse Compton origin; (2) GRB should have multi-zone emission region, with MeV emission produced at smaller radii while optical and > 100 MeV emission at larger radii; (3) the bulk Lorentz factor can be a few 100's, much lower than 10 3 , in multi-zone model; (4) the upstream magnetic field of afterglow shock is strongly amplified to be at least in mG scale.

关键词： Gamma-ray burst high energy Fermi/LAT

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Measurement of the high-energy gamma-ray emission from the Moon with the Fermi Large Area Telescope

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Physical Review D 2016年第8期93卷 082001-082001页

作者： M. Ackermann M. Ajello A. Albert W. B. Atwood L. Baldini G. Barbiellini D. Bastieri R. Bellazzini E. Bissaldi R. D. Blandford R. Bonino E. Bottacini J. Bregeon P. Bruel R. Buehler G. A. Caliandro R. A. Cameron M. Caragiulo P. A. Caraveo E. Cavazzuti C. Cecchi A. Chekhtman J. Chiang G. Chiaro S. Ciprini R. Claus J. Cohen-Tanugi F. Costanza A. Cuoco S. Cutini F. D’Ammando A. de Angelis F. de Palma R. Desiante S. W. Digel L. Di Venere P. S. Drell C. Favuzzi S. J. Fegan W. B. Focke A. Franckowiak S. Funk P. Fusco F. Gargano D. Gasparrini N. Giglietto F. Giordano M. Giroletti T. Glanzman G. Godfrey I. A. Grenier J. E. Grove S. Guiriec A. K. Harding J. W. Hewitt D. Horan X. Hou G. Iafrate G. Jóhannesson T. Kamae M. Kuss S. Larsson L. Latronico J. Li L. Li F. Longo F. Loparco M. N. Lovellette P. Lubrano J. Magill S. Maldera A. Manfreda M. Mayer M. N. Mazziotta P. F. Michelson W. Mitthumsiri T. Mizuno M. E. Monzani A. Morselli S. Murgia E. Nuss N. Omodei E. Orlando J. F. Ormes D. Paneque J. S. Perkins M. Pesce-Rollins V. Petrosian F. Piron G. Pivato S. Rainò R. Rando M. Razzano A. Reimer O. Reimer T. Reposeur C. Sgrò E. J. Siskind F. Spada G. Spandre P. Spinelli H. Takahashi J. B. Thayer D. J. Thompson L. Tibaldo D. F. Torres G. Tosti E. Troja G. Vianello B. L. Winer K. S. Wood M. Yassine F. Cerutti A. Ferrari P. R. Sala Deutsches Elektronen Synchrotron DESY D-15738 Zeuthen Germany Department of Physics and Astronomy Clemson University Kinard Lab of Physics Clemson South Carolina 29634-0978 USA W. W. Hansen Experimental Physics Laboratory Kavli Institute for Particle Astrophysics and Cosmology Department of Physics and SLAC National Accelerator Laboratory Stanford University Stanford California 94305 USA Santa Cruz Institute for Particle Physics Department of Physics and Department of Astronomy and Astrophysics University of California at Santa Cruz Santa Cruz California 95064 USA Università di Pisa and Istituto Nazionale di Fisica Nucleare Sezione di Pisa I-56127 Pisa Italy Istituto Nazionale di Fisica Nucleare Sezione di Trieste I-34127 Trieste Italy Dipartimento di Fisica Università di Trieste I-34127 Trieste Italy Istituto Nazionale di Fisica Nucleare Sezione di Padova I-35131 Padova Italy Dipartimento di Fisica e Astronomia “G. Galilei” Università di Padova I-35131 Padova Italy Istituto Nazionale di Fisica Nucleare Sezione di Pisa I-56127 Pisa Italy Istituto Nazionale di Fisica Nucleare Sezione di Bari I-70126 Bari Italy Istituto Nazionale di Fisica Nucleare Sezione di Torino I-10125 Torino Italy Dipartimento di Fisica Generale “Amadeo Avogadro” Università degli Studi di Torino I-10125 Torino Italy Laboratoire Univers et Particules de Montpellier Université Montpellier CNRS/IN2P3 F-34095 Montpellier France Laboratoire Leprince-Ringuet École polytechnique CNRS/IN2P3 F-91128 Palaiseau Cedex France Consorzio Interuniversitario per la Fisica Spaziale (CIFS) I-10133 Torino Italy Dipartimento di Fisica “M. Merlin” dell’Università e del Politecnico di Bari I-70126 Bari Italy INAF-Istituto di Astrofisica Spaziale e Fisica Cosmica I-20133 Milano Italy Agenzia Spaziale Italiana (ASI) Science Data Center I-00133 Roma Italy Istituto Nazionale di Fisica Nucleare Sezione di Perugia I-06123 Perugia Italy Dipartimento di Fisica Università degli Studi di Perugia I-06123 Perugia

We have measured the gamma-ray emission spectrum of the Moon using the data collected by the Large Area Telescope onboard the Fermi satellite during its first seven years of operation, in the energy range from 30 MeV up to a few GeV. We have also studied the time evolution of the flux, finding a correlation with the solar activity. We have developed a full Monte Carlo simulation describing the interactions of cosmic rays with the lunar surface. The results of the present analysis can be explained in the framework of this model, where the production of gamma rays is due to the interactions of cosmic-ray proton and helium nuclei with the surface of the Moon. Finally, we have used our simulation to derive the cosmic-ray proton and helium spectra near Earth from the Moon gamma-ray data.

关键词： Cosmic ray sources Cosmic rays & astroparticles Gamma ray astronomy Solar cycles

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The lifetime of contact binaries

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Proceedings of the International Astronomical Union 2013年第S290期8卷 229-230页

作者： D. K. Jiang Z. W. Han L. H. Yang L. F. Li National Astronomical Observatories Yunnan Observatory Chinese Academy of Sciences P.O. Box 110 Kunming. e-mail: dengkai@*** Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences National Astronomical Observatories Chinese Academy of Sciences Beijing 100012 China

The lifetime of contact binaries is an important parameter for studying the evolution of contact binaries. By reproducing the relative frequency of occurrence for contact binaries, we found that the lifetime of contact binaries decreases with increasing mass of the primaries. The lifetime of contact binaries is about 4%–10% of the main sequence lifetime of the primaries, and is about 0.006–0.65 Gyr. This suggests that the lifetime of contact binaries strongly depends on the mass of the primaries.

关键词： Binaries: close binaries: eclipsing stars: evolution

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The criteria for dynamical mass transfer of the main-sequence donor stars

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Proceedings of the International Astronomical Union 2013年第S290期8卷 213-214页

作者： H. Ge R. F. Webbink X. Chen Z. Han National Astronomical Observatories/Yunnan Observatory Chinese Academy of Sciences Kunming 650011 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming 650011 China Department of Astronomy University of Illinois 1002 W. Green St. Urbana IL 61801 USA

Mass transfer is very common in binary evolution and it dominates the evolutionary fate of binaries. Two crucial problems i.e. dynamical mass transfer and common envelope evolution, are not well understood yet. Here we focus on the first problem, and systematically show the critical mass ratio for dynamical mass transfer when the donor stars are still on the main sequence (MS).

关键词： Binaries:close stars:evolution stars:mass-loss stars:interios

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A new photometric study of the triple star system EF Draconis

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Research in Astronomy and Astrophysics 2012年第4期12卷 419-432页

作者： Yuan-Gui Yang School of Physics and Electronic Information Huaibei Normal UniversityHuaibei 235000China Key Laboratory of the Structure and Evolution of Celestial Objects Chinese Academy of SciencesKunming 650011China

We present new charge-coupled device （CCD） photometry for the triple star EF Draconis, obtained in 2009 and 2011. Using the updated Wilson-Devinney program, the photometric solutions were deduced from two sets of light curves. The results indicate that EF Dra is an A-type W UMa binary with a contact degree of f = 46.7%（ ± 0.6%） and a third light of l 3 ■1.5%. Through analyzing the O C curve, it is found that the orbital period shows a long-time increase with a lighttime orbit. The period, semi-amplitude and eccentricity of the third body are P mod = 17.20（ ± 0.18） yr, A = 0.0039 d （ ± 0.0002 d ） and e = 0.49（ ± 0.02） respectively. This kind of tertiary companion may extract angular momentum from the central system. The orbital period of EF Dra secularly increases at a rate of dP/dt = ＋3.72（ ± 0.07） × 10 7 d yr 1 , which may be interpreted by mass transfer from the less massive to the more massive component. As period increases, the separation between components may increase, which will cause the contact degree to decrease. With mass transferring, the spin angular momentum will increase, while the orbital angular momentum will decrease. Only if the contact configuration would merge at J spin 〉1/3 J orb could this kind of deep-contact binary with period increasing, such as EF Dra, evolve into a rapidly-rotating single star.

关键词： stars （including multiple）： binaries： close — stars： individual （EF Draconis）

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Spectral cutoffs of Fermi-LAT GRBs 080916C and 090926A

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Research in Astronomy and Astrophysics 2012年第11期12卷 1519-1525页

作者： Biao Li Zhuo Li Department of Astronomy/Kavli Institute for Astronomy and Astrophysics Peking UniversityBeijing 100871China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy ofSciencesKunming 650011China

It is expected that there should be a spectral cutoff at the high energy end of emission from a prompt gamma-ray burst （GRB）, due to, e.g. γγ absorption and/or a high energy cutoff in the electron distribution. We analyze the spectral data of Fermi- LAT detected GRBs 080916C and 090926A, aiming at locating the spectral cutoff. By assuming that the prompt GRB spectrum at the high energy end is a power law with an exponential cutoff, our analysis finds that the cutoff energy Ecutoff depends on the photon index/3 and the cutoff occurs at very high energy, Ecutoff = 161＋533 GeV in GRB 080916C and Ecutoff ≥ 100 GeV （forβ ≈-2.3） in GRB 090926A. Such high energy photons, if they exist, may disfavor the synchrotron origin and need alternative generation mechanisms.

关键词： gamma-rays： bursts -- acceleration of particles

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The evolution of Cataclysmic Variables

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Proceedings of the International Astronomical Union 2013年第S290期8卷 253-254页

作者： Lifang Li Fenghui Zhang Zhanwen Han National Astronomical Observatories/Yunnan Observatory CAS P.O. Box 110 Kunming Yunnan Province 650011 P.R. China (email: llf@***) Key Laboratory for the Structure and Evolution of Celestial Objects CAS P.O. Box 110 Kunming Yunnan Province 650011 P.R. China

Using Eggletons code the evolution of cataclysmic variables (CVs) is investigated. CVs might suffer the loss of mass and angular momentum during their evolution, we present the models of CVs with mass loss and angular momentum loss (AML) due to gravitation wave radiation (GR) and/or magnetic braking (MB). It is found that the loss of mass and angular momentum has significant influence on the evolution of CVs, and that the change of the star structure or their atmosphere properties is a possible mechanism which underlies a sudden change in the rate of AML owing to MB.

关键词： Stars: cataclysmic variables stars: evolution stars: magnetic fiels stars: mass-loss

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A POSSIBLE EXPLANATION OF ENERGY DEPENDENCE OF GRB PULSE WIDTH

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International Journal of Modern Physics: Conference Series 2013年第23期ijmpcs卷 301-303页

作者： XIAO-HONG ZHAO ZHAO-YANG PENG National Astronomical Observatories/Yunnan Observatory Chinese Academy of Sciences P. O. Box 110 Kunming 650011 China Key Laboratory for the Structure and Evolution of Celestial Bodies Chinese Academy of Sciences P.O. Box 110 650011 Kunming China Department of Physics Yunnan Normal University Kunming 650092 China

Previous studies have found that the width of gamma-ray burst (GRB) pulse is energy dependent 1-2 and its origin keeps unknown. Here we find combining the curvature effect and the intrinsic Band spectrum could naturally result in the energy dependence of GRB pulse width. Our result suggests that the GRB decay phase is indeed related to the so-called curvature effect. A natural expectation of our study is for bursts with single power law, not Band spectrum, pulse width will not be energy dependent in our consideration.

关键词： Gamma rays bursts

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A test of an early-type contact binary model by comparing the relations obtained from theory with those from observations

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Science China(Physics,Mechanics & Astronomy) 2012年第2期55卷 320-328页

作者： SONG Fen HUANG RunQian Department of Astronomy Beijing Normal UniversityBeijing 100875China National Astronomical Observatories/Yunnan Observatory Chinese Academy of SciencesKunming 650011China Key Laboratory of the Structure and Evolution of Celestial Objects Chinese Academy of SciencesKunming 650011China

Contact binary systems,including massive,middle-mass and low-mass systems,have been *** is necessary to construct the evolutionary model for contact binary systems with all different *** model introduced by Huang,Song and Bi indicates some special and unique understandings of the physical processes occurring in the contact *** is necessary to test whether this model can be applied to the early-type contact *** best way to test a theoretical model is to know whether this model can explain the observational phenomena of such *** this aim,a comparison is performed for the relations of mass-luminosity,mass-radius,and the distribution in the HR diagram obtained from the model introduced by Huang et *** those from the astronomical observations.A good result is obtained by the *** means the model can be used in calculating the evolution of early-type contact binaries,and can explain the observational phenomena of such binaries.

关键词： binaries： eclipsing stars： evolution stars： fundamental parameters stars： rotation

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