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研究生： 葉文豪
Wen-Hao Yeh
論文名稱：
Numerical Simulations of Binary Accretion Disks
指導教授： 江瑛貴
Ing-Guey Jiang
口試委員:
學位類別： 碩士
Master
系所名稱： 理學院 - 天文研究所
Graduate Institute of Astronomy
畢業學年度： 93
語文別： 英文
論文頁數： 64
外文關鍵詞： accretion disk
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    • 1980年代之後，不論是理論天文學家或是觀測天文學家，對矮新星中吸積盤的不穩定性都很有興趣。
    由於雙星中成員星的演化，將會影響到雙星的光變曲線。在激變星中，尤其是SU UMa這類型的星，在光度上的變化完全由於環繞著主星(白矮星)的吸積盤所造成的。
    當雙星中的次星離開了主序帶之後，便會開始膨脹並且中滿了整個洛西瓣，並且次星上的物質便會通過Lagrange點，並進入主星的洛西瓣中。由於角動量的守衡，這些物質便會環繞主星並形成吸積盤。
    我們使用ER UMa這類型的星的參數模擬出吸積盤的形成、進動以及熱點，並且模擬出可能的光度曲線。

    After 1980s, the instabilities of accretion discs in dwarf novae interest both theoreticians and observers very much.
    The evolutin of stars in binary systems would affect the light curves. In cataclysmic variables (CVs), especially SU UMa type stars, the change of its luminosity is completely determined by the accretion disc around the primary star, i.e. the white dwarf.
    The secondary star leaves the main sequence and expands its photosphere to touch the Roche-lobe. Its mass transfers through the Lagrange point and goes into the primary''s Roche-lobe. Due to the conservation of angular momentum, the mass goes around primary and form and accretion disc.
    We follow the parameters of ER UMa stars to study the formation, precession, and hot spot of accretion discs and produce the possible light curves for two different models.

    1 Introduction.........................................................1 1.1 Characteristic of Dwarf Novae lightcurve.............................1 1.2 Structure of Dwarf Novae.............................................2 2 Numerical Methods....................................................4 2.1 The Gravitational Force..............................................4 2.2 Hydrodynamics........................................................6 2.3 SPH..................................................................7 2.4 Runge-Kutta Method..................................................9 3 Numerical Tests.....................................................10 3.1 The Test of Gravity.................................................10 3.2 The Test of Viscosity...............................................10 3.2.1Initial Particle Distribution.......................................12 3.2.2The Results.........................................................14 3.3 The Test of Periodicity Analysis....................................16 4 Simulations of ER UMa stars.........................................19 4.1 Initial Condition...................................................19 4.1.1Initial Condition...................................................19 4.1.2Mass Transfer.......................................................19 4.1.3The Live Particles..................................................21 4.1.4Simulations of Outburst.............................................22 4.2 Simulation Result...................................................23 4.2.1The Disc Formation..................................................25 4.2.2The Disc Precession.................................................28 4.2.3The Hot Spot........................................................28 4.2.4Lightcurves.........................................................28 5 Data Analysis.......................................................42 5.1 Periodicity Analysis of Whole Data..................................42 5.1.1ER UMa..............................................................42 5.1.2RZ LMi..............................................................43 5.2 Periodicity Analysis of Detail Data.................................43 5.2.1ER UMa..............................................................47 5.2.2RZ LMi..............................................................47 6 Conclusion and Futer Work...........................................62 6.1 Conclusion..........................................................62 6.2 Future Work.........................................................62 Bibliography.................................................64

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