Polarization Changes of Pulsars due to Wave Propagation through Magnetoshperes

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1 Origin of pulsar orthogonal polarization modes Chen WANG P.F. WANG, Wei WANG, Jinlin HAN National Astronomical Observatories, CAS 3 rd US-Chinese Workshop, GBT, WV

2 Outline Polarized Curvature Radiation in Pulsar Magnetosphere (with both emission and propagation). => naturally generate orthogonal polarization modes (OPM) Wang, Wang & Han, 2014 Distinguish orthogonal polarization modes of pulsar emission using spin axis and proper motion => constrain OPM model Wang 2014

=> naturally generate orthogonal polarization modes (OPM) Wang, Wang & Han,

3 Basic Physical Image of polarization evolution Pulsar magnetosphere 1) Rotating dipole 2) ±e plasma streaming along B field line 3) Lorentz factor of the plasma γ ~ 400; 4) Density of the plasma Ω B μ k Emission Curvature radiation Propagation 1) O mode refraction 2) Adiabatic walking

$Curvature radiation Propagation 1) O mode refraction 2) Adiabatic$

4 Two linear eigenmodes of wave in pulsar magentosphere k Ordinary mode (), n < 1 Extraordinary mode (), n ~ 1 Refraction of wave Ω μ X O X O B observer The separation between the emission points of the O/ waves B Observed O/ components at given phase are incoherent!

X O X O B observer The separation between the emission points of

5 1/γcone Curvature Radiation Without co-rotation V0 // B V0 1/γ 1/γcone B Classical model considered by Cheng & Ruderman 1979 With co-rotation V // B V0 V B

6 Without co-rotation Emission beam Profiles with various impact angle Uniform Cone Core Patch

7 With co-rotation Emission beam Profiles with various impact angle Uniform Cone Core Patch

8 Conclusion for polarized curvature radiation in pulsar magnetosphere The refraction separate X and components. which cause: The observed and wave at given phase are emitted from incoherent region; The orthogonal mode happens naturally due to the change of the dominance of the two modes; X/ components of CR have: almost the same magnitude without considering the co-rotation of plasma, which cause strong depolarization; very different distribution with co-rotation included, high LP can be observed. Refraction induced OPM perfers O X O modes sequence. May be checked by observation!

the dominance of the two modes; X/ components of CR have: almost the same magnitude without considering the co-rotation of plasma, which cause

9 Distinguish orthogonal polarization modes of pulsar emission Orthogonal polarization mode for PSR B Mean profile Polarization of single pulses V PA L Which mode is it? O- or? PA 90 o 90o I Stinebring et al. (1984)

10 Rotating Vector Model

11 Two ways to constrain spin axis Get spin axis directly by fitting the symmetric tori of PWNe around some young pulsars obtain spin axis of 15 pulsars by Ng & Romani 2004, 2007, Not avialable for normal pulsars without PWNe Using proper motion direction instead of spin axis according to spin-kick alignment Spin-kick alignment proved by Romani, Ng, Johnston, Wang, Noutsos et al. Proper motion measured by pulsar timing and interferometer obs. Brisken et al. 2002, 2003; Hobbs et al PWN of Vela: X-ray obs. Ng & Romani 2004 Spin-kick alignment of pulsars Noutsos et al. 2011

Not avialable for normal pulsars without PWNe Using proper motion direction instead of spin axis according to spin-kick alignment Spin-kick

12 Mode distinguishment for 14 OPM-pulsars (with both believable PM and PA data) For 7 pulsars, dominate central intensity-peak region. (X O X) For 4 pulsars, dominate intensity-peak region. (O X O) For 3 pulsars, each mode dominates half profiles Polarization profiles comes from Johnston et al. 2005, 2007; Carr 2007; Han et al. 2009

(X O X) For 4 pulsars, dominate intensity-peak region.

13 Possible constrains on origin of OPM Refraction effect. O-X-O (4 pulsars) O mode refracted towards away from magnetic axis. Emission mechanism origin. Cheng & Ruderman 1979, X-O-X (7 pulsars) Central emission from parallel accelaration from curvature radiation dominates two wings PSR Different OPM-pulsars may have different origin of OPM.

14 Summary Refraction of seperates the two eigenmodes and make them incoherent, which naturally causes OPM. X/ components of curvature radiation have: almost the same magnitude without considering the co-rotation of plasma, which cause strong depolarization; very different distribution with co-rotation included, high LP can be observed. Modes sequence of OPM perfer O X O Polarization modes of 14 OPM-pulsars can be recognized by pulsar spin axis and/or proper motion. 4 of them agree with O X O modes sequence 7 of them are X O X, 3 of them are X O. Different OPM-pulsars may have different origin of OPM.

very different distribution with co-rotation included, high LP can be observed.

16 年轻脉冲星星风云 X-ray 观测 Crab PA rot Vela PA rot 部分 PWN 为环状结构可以直接确定自转轴方向 B B J J J B J J Kargaltsev & Pavlov 2008 B J B B

J1833-1034 J0205+6449 J2229+6114 B1509-58 J1124-5916

17 Mode distinguishment for 3 young pulsars Both spin axis and well-calibrated polarization position angle curve is needed

18 普通脉冲星 :spin-kick 趋于一致利用偏振曲线最陡处 PA 0 代替 spin, 统计 PA 0v 的分布 Wang et al Johnston et al. 2005

19 讨论利用自行与 PA 最陡处偏振位置角之差 (PA 0v ) 辨别模式的前提 : Spin-kick 趋于一致是否可靠? 年老的脉冲星可能不一致部分年轻或正常脉冲星也有可能不一致传播效应对 PA 曲线垂直方向影响不大基本可靠! 确定 PA 曲线最陡处的位置对基本符合 RVM 描述的 S 型比较容易但是对 S 曲线不完整的比较勉强! 下一步工作 : 获得更大的 PA 0v 样本偏振观测与校准多波段偏振观测自行观测数据, 长期 timing 或者 VLBI 观测获得下一步工作 : 正交模式的起源正在进行中

确定 PA 曲线最陡处的位置对基本符合 RVM 描述的 S 型比较容易但是对 S 曲线不完整的比较勉强!

20 总结利用年轻脉冲星星风云 X-ray 观测得到的自转轴方向可以辨别偏振模式, 但是个数太少根据 spin-kick 的一致性, 可以利用自行方位与 PA 最陡处偏振位置角之差 (PA 0v ) 来辨别偏振模式 PA 0v ~ 0 o 为 PA 0v ~ 90 o 为应用 : 利用 PA 0v 辨别了 12 颗脉冲星的正交模式, 发现 8 颗脉冲星位于 leading side 4 颗脉冲星位于 leading side 利用 PA 0v 辨别了 4 颗 conal-double PSRs 的偏振模式, 有 3 颗是需要更多的校准好的偏振数据以及自行数据进行下一步统计研究

PA 0v 辨别了 12 颗脉冲星的正交模式, 发现 8 颗脉冲星位于 leading side 4 颗脉冲星位于 leading side 利用 PA 0v

21 Cheng & Ruderman 1979 curvature dominate Bunching dominate

22 星风云的详细结构

23 Vela 脉冲星星风云的结构 G. G. Pavlov et. al. ApJ. 591:1157 C.-Y. Ng ApJ.601:479 (FITTING PWN TORI) Chandra ACIS-S3 image of Vela PWN:(1) Vela pulsar, (2) inner arc, (3) outer arc, (4) inner jet, (5) counter jet, (6) shell, (7) outer jet.

24 考虑 spin-kick 的一致性, 可以用自行代替自转轴方向判断自行方向角 PA v 与 PA 最陡处 PA 0 的差值 PA 0v PA 0v ~ 0 o => PA 0v ~ 90 o => PA v PA v Two Velalike PSRs PA v

25 应用 PA 0v 辨别正交模式 B B PA v

26 B B PA v

27 PA v? B B

28 B J PA v 8 颗脉冲星位于 leading side

29 J J PA v

30 J J PA v 4 颗脉冲星位于 leading side 8 颗脉冲星位于 leading side

31 Conal-Double PSRs 中 PA 与 V 的关系 Conal-double pulsars, PA increase V < 0 PA decrease V > 0 PAv 可以利用磁层中的波模耦合传播效应来很好的解释波模耦合产生的圆偏振依赖于 PA 的变化趋势 Han et al. 1998, You et al 要求 :Conal-Double PSRs 的偏振辐射都是! 可以用 PA 0v 来检验是否为

32 PA 0v = 21 o ( 15) PA 0v = 16 o ( 7) 4 颗 conal-double PSRs 有 PA 0v 3 颗为, 1 颗为 PA 0v = -67 o (2) PA 0v = 1 o (10)

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