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闫文明 中国科学院新疆天文台 19/08/2013 NAOC, Beijing
毫秒脉冲星的偏振观测 闫文明 中国科学院新疆天文台 19/08/ NAOC, Beijing
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偏振 电矢量振动方向对于传播方向的不对称性叫做偏振，它是横波区别于其他纵波的一个最明显的标志。
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偏振光的描述方法 经典方法 斯托克斯参数法 I：总强度 (Q2+U2)1/2: 线偏振成分的强度 V：圆偏振成分的强度
tan-1(U/Q)/2:线偏振位置角
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斯托克斯参数的性质 自然光：｛I，0，0，0｝ 强度为I的自然光可看作是两束强度相等、不相干的反向偏振光｛I/2,Q,U,V｝和｛I/2,-Q,-U,-V｝的混合。 任意偏振光｛I,Q,U,V｝可以分为一束自然光｛I-(Q2+U2+V2)1/2,0,0,0｝和一束完全椭圆偏振光｛(Q2+U2+V2)1/2,Q,U,V｝, 或者一束自然光｛I-(Q2+U2+V2)1/2-|V|,0,0,0｝和一束完全线偏振光{(Q2+U2+V2)1/2,Q,U,0}以及一束完全圆偏振光{|V|,0,0,V}。
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Polarization measurements
Radio telescopes usually take measurements in two orthogonal polarizations. For a dual-linear feed For a dual-circular feed
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法拉第旋转效应 β=RM·λ2
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脉冲星的周期分布 Normal pulsars Millisecond pulsars
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P-Pdot diagram Harding 2013
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Duty cycle (W/P) Kramer et al. 1998
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光速圆柱半径
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Pulsar emission beam Gil et al
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Opening angle Kramer et al. 1998
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Interpulse The secondary pulses separated by about
180°from the main pulse. The main pulse and interpulse originate from oppsite magnetic poles. While only about 2% of all normal pulsars are known to exhibit interpulses or pre- or postcursors, about 36% of all Galactic MSPs known either emit a post or precursor or exhibit an interpulse. Kramer et al. 1998
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Rotating Vector Model （Radhakrishnan & Cooke 1969）
Von Hoensbroech & Xilouris 1997
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Polarization similarity
Han et al Ord et al. 2004
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Parkes Pulsar Timing Array project
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PPTA脉冲星的偏振轮廓 Yan et al. 2011a
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PA variations with time
Long-term changes in pulsar PAs can result from changes in the polarization of the emitted radiation or from changes in the RM along the path. PA=RM·λ2 Intrinsic PA changes could result from precession of the pulsar spin axis or changes in the magnetic configuration of the star. RM changes can occur as the path to the pulsar traverses different regions of the interstellar medium (ISM) or in certain changes the Earth’s ionosphere.
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Vela pulsar (PSR B0833-45) discovered in 1968, 89ms
near the center of the Vela nebula Hamilton et al .1985
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双脉冲星系统 J0737-3039 discovered in 2003,22.7ms, 2.77s
a laboratory for strong-field gravity and plasma physics Yuen et al. 2012
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PA variations for PPTA pulsars
Yan et al. 2011b
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总结 毫秒脉冲星的偏振性质和普通脉冲星是相似的，说明两类脉冲星基本的辐射机制是相同的
然而毫秒脉冲星的偏振位置角和轮廓形状比普通脉冲星复杂，说明毫秒脉冲星的辐射区结构更复杂 经过电离层修正以后，PPTA毫秒脉冲星的偏振位置角没有显著的随时间长期变化的趋势，说明不仅PPTA脉冲星发出的偏振辐射本身是稳定的，并且视线穿过的星际介质贡献的RM的长期净变化也非常小
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Thanks for your attention!
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