臺灣博碩士論文加值系統

我們發展一強磁場中子星大氣模型,其大氣組成為純氫.假設氫完全游離下，不透明度(opacity)只考慮湯姆森散射(Thomson scattering)和自由-自由吸收(free-free absorption)．與其他模型不同處為：物態方程(equation of state)已併入庫倫力的修正；且我們的大氣模型可允許任意的磁場方向．
此論文中已算出磁場B=10^12G，表面有效溫度為10^6K，表面重力g*=GM/(R^2)(1-2GM/(Rc^2))=10^13 cm/sec^2， 磁場方向垂直星球表面下的光譜．所考慮的頻率範圍為10^16Hz~10^19Hz．結果呈現星球表面光譜輻射方向和星球表面的夾角愈大，強度愈小，即所謂的limb darkening現象．
此外，隨輻射方向和磁場夾角不同，光譜偏極化程度亦不同．和磁場夾角愈大時，偏極化愈強，光譜主要為X-mode(當電磁波在強磁場電漿中傳播，會存在兩種模態，為 X-mode 及 O-mode．),因為光的頻率遠小於電子的cyclotron 頻率(eB/mc)時，O-mode的不透明度遠大於X-mode．另外，和相同溫度黑體輻射的光譜比較，此模型所得光譜在頻率較高波段的強度較強．而且在cyclotron 頻率時，光譜有吸收譜線．

We develop an atmosphere model for neutron stars with strong magnetic fields.　The atmosphere is composed of pure hydrogen.　We assume it is fully ionized and the opacity considered is contributed from　the Thomson scattering and free-free　absorption.　The equation of state has incorporated Coulomb correction.　We have allowed an arbitrary magnetic field direction in our codes for solving the　radiation transfer equation. In this paper,we have performed a computation with a magnetic field of　10^12 G, effective temperature 10^6 K and surface gravity　g*=GM/(R*R)(1-2GM/(Rc^2))=10^13 cm/sec^2. The
angle between the magnetic field and the surface normal is
90 degree. The computed emergent spectra exhibit a high degree of polarization, limb darkening, high-energy bumps, and cyclotron lines. In addition, the polarization also depends on the viewing angles. Our current work forms the basis for more comprehensive studies in the future.

1 Introduction
2 Physics in a Uniformly Magnetized and Cold Plasma
2.1 The Normal Modes and Longitudinal Field
2.2 The Thomson Scattering Cross Section
2.3 The Free-Free Absorption Cross Section
2.4 The Electrostatic Correction to the Equation of State
3 Atmosphere Model Computation
3.1 Basic Physical Quantity
3.2 The Mean Opacity and the Gray Atmosphere
3.3 The Equation of Hydrostatic Equilibrium
3.4 The Equation of Radiation Transfer
4 Numerical Methods
4.1 The Riccati Transform
4.2 The Temperature Correction Procedure
5 Results and Discussion
5.1 Main Results
5.2 Discussion
Appendix A Wave Propagation in a Cold Magnetized Plasma
Appendix B The Transformation between the Frames with Different Definitions

Alcock, C., Illarionov, A., 1980, ApJ 235, 534
Becker, W., Trumper, J., 1997, A&A 326, 682
Bignami, G. F., Caraveo, P. A., De Luca, A., Mereghetti, S., 2003, Nature 423, 725
Chang, H. K., 2001, Chinese Journal of Physics 40, 395
Clayton, D.D., 1968, Principles of stellar Evolution and Nucleosynthesis (McGraw-Hill: London)
Ginzburg, V.L., 1964, Electromagnetic Waves in Plasmas(Fizmatgiz: Moscow)
Ho, Wynn C. G., Lai, Dong, 2001, MNRAS 327, 1081
Marshall, H. L., Norbert, N. S., 2002, ApJ 574,377
Meszaros, P., 1992, High-Energy Randiation from
Magnetized Nuetron Starts (University Chicago pree: Chicago)
Mihalas, D., 1970, Stellar Atmospheres (W.H. Freeman and Co.: San Francisco)
Miller, M. C., 1992, MNRAS 255, 129
Pavlov, G. G., Shibanov, Yu. A., Ventura, J., Zavlin, V. E., 1994, A&A 289, 837
Rajagoal, M., Romani, R. W., 1996, ApJ 461, 327
Rajagoal, M., Romani, R. W., Miller, M. C., 1997, ApJ 479, 347
Romani, R. W., 1987, APJ 313, 718
Shibanov, Yu. A., Zavlin, V. E., Pavlov, G. G., Ventura, J., 1992, A&A 266, 313
Zavlin, V. E., Pavlov, G. G.,Shibanov, Yu. A., 1996, A&A 315, 141