1、1 1、脉冲星的基本特性、脉冲星的基本特性2 2、脉冲星的观测结果、脉冲星的观测结果3 3、描述脉冲星高能辐射的模型、描述脉冲星高能辐射的模型 外间隙模型外间隙模型内容内容1 1）中子星观念的提出中子星观念的提出1 1、脉冲星的基本特性、脉冲星的基本特性Baade & Zwicky (1934)提出宇宙中存在中子星 Oppenheimer & Volkoff (1939)估计了中子星的第一个态方程：质量 1.4 太阳质量；半径 10 公里；密度1014 g cm -3 .Pacini (1967) Pacini (1967) 提出来自转动的中子星的电磁提出来自转动的中子星的电磁辐射可以驱动辐射
2、可以驱动CrabCrab星云星云 Pulses from the Vela Pulsar2 2）脉冲星的发现）脉冲星的发现19671967年，年，Jocelyn BellJocelyn Bell每天每天早上在射电望远镜早上在射电望远镜中都观测到短的、规则的、象时钟一样的辐射中都观测到短的、规则的、象时钟一样的辐射脉冲。脉冲。Hewish Hewish 等人等人 ( (Hewish et al. 1968,NatureHewish et al. 1968,Nature) )发现发现了了一颗一颗射电射电发射的快速脉冲源发射的快速脉冲源PSR B1919+21.PSR B1919+21. Gold
3、(1968, Nature) Gold (1968, Nature) 指出脉冲星就是表面磁指出脉冲星就是表面磁场场1012G1012G的的中子星。中子星。3 3）脉冲星的分类）脉冲星的分类 孤立中子星：孤立中子星： 通过快速自转变慢辐射能量通过快速自转变慢辐射能量（一般（一般 0) 0) 。 脉冲脉冲X X射线源：射线源： 双星系统中的致密天体（双星系统中的致密天体（一般为中子星）；从正常伴星中吸积物质一般为中子星）；从正常伴星中吸积物质(P10s secs, dP/dt0) dP/dt0) 。 已观测到大部分脉冲星自转变慢，即已观测到大部分脉冲星自转变慢，即dP/dt0dP/dt0。所以它们
4、损失转动能可以说明观。所以它们损失转动能可以说明观测吗？测吗？2222224221PIPIIEdtdPPIPIdtddtdE322242 转动磁偶极子的能损：转动磁偶极子的能损： 磁场与周期和周期倒数的关系：磁场与周期和周期倒数的关系： 脉冲星年龄的估算：脉冲星年龄的估算： Pulsar pictureLight cylinderOpenmagnetosphereRadio beamr=c/ BClosed magnetosphereNeutron starmass = 1.4 solar massesradius = 10 kmB = 10 to 10 Tesla49Pulsar model
5、2 2、脉冲星的观测结果、脉冲星的观测结果1）射电波段： 2）X射线波段：51颗X射线脉冲星彩色的符号表示探测彩色的符号表示探测到到X X射线脉冲射线脉冲转动驱动的脉冲星分布转动驱动的脉冲星分布28颗正常脉冲星 23颗毫秒脉冲星3 3）高能伽玛射线：）高能伽玛射线：History: SAS 2, COSB(1970s-1980s). EGRET (1990s)Coming satellite: GLAST（1）EGRET观测成果Increased number of IDs sources by large factors发现了170颗未证认的伽玛射线源（2 2）观测到的伽玛射线脉冲星）观测到
6、的伽玛射线脉冲星 Crab脉冲星 Vela脉冲星 PSR B150958 PSR B104658 PSR B170644 PSR B195132 PSR B105552 Geminga脉冲星Pulses at multi-wavebandsEnergy spectra of gamma-ray pulsars3 3、描述脉冲星高能辐射的模型、描述脉冲星高能辐射的模型目前有两类公认的模型：目前有两类公认的模型：（1 1） 内间隙模型内间隙模型 (Harding et al. 1978, ApJ 225, 226; Daugherty & Harding 1982 ApJ 252, 337;199
7、6 ApJ 458, 278; Zhang & Harding, 2000, ApJ; Sterner et al. 1995, ApJ 445, 736).（2 2）外间隙模型）外间隙模型 (Cheng, Ho, Ruderman ,1986, ApJ 300, 500; 300, 522; Chiang & Romani 1994, ApJ 436, 754; Romani, 1996, ApJ 470, 469, Zhang & Cheng 1997, ApJ 487 370; Hirotani & Shibata 2001, MNRAS 325, 1228)Schematic geom
8、etry of polar and outer gaps. Dark solid regions are thin gaps of younger pulsars. Hatched regions are thick gaps of older pulsars正负电子由外间隙中正负电子由外间隙中 E E|加速加速相对论性相对论性 e e+ +/e/e- -通过同步曲率辐射通过同步曲率辐射和和ICIC过程产生高能伽玛射线过程产生高能伽玛射线来自表面的软来自表面的软X X射线由回流电流与射线由回流电流与NSNS表面碰撞产生。在外间隙中高表面碰撞产生。在外间隙中高能伽玛射线与这些软能伽玛射线与这些软
9、X X射线碰撞产射线碰撞产生正负电子对，从而维持外间隙生正负电子对，从而维持外间隙存在。存在。Outer gap size：Luminosity：Spectrum1) Conversion efficiency of gamma-ray pulsars.2) The statistics of gamma-ray pulsars.3) Radiation features of X-ray pulsars.4) The statistics of X-ray pulsars.5) The contribution of gamma-rays from pulsars to Galactic g
10、amma-rays. 6) The contribution of positrons from pulsars to Galactic positrons. 7) Unidentified gamma-ray sources and gamma-ray pulsars.3D magentic structure, the phase profile and phase-resolved spectra. Application to Crab pulsar. Phase-resolved high-energy features of Crab-like pulsars.Phase-reso
11、lved high-energy features of Geminga pulsar.Zhang, L. & Cheng, K.S. 2002, ApJ, 569, 872Cheng & Zhang, 2001, ApJ, 562, 918Zhang, & Cheng,2002, ApJ, 579, 716弱磁场，短周期Zhang & Cheng, K.S. 2003, A&A, 398, 639magnetosphere geometry inclination effectObservation indicates (Thompson et al. 2001): L L sd .ZC97
12、 model predicts L (B/P) 0.3, e.g, the ratio of (B/P) 0.3 for PSR B1055-52 to that for Geminga is 0.9. But, the observed ratio 8 (Kaspi et al. 2000).Outer gap:Outer gap: f0 (P, B) = 5.5 P 26/21 B -4/712Gamma-ray LuminosityRadio-loud : L L 0.30 sd Radio-quiet : L L 0.38 sd Solid line:lg L 20.42+0.38lg
13、 LsdDashed line: lg L 3.25+0.30lg LsdDeath lines of the pulsars with self-sustained outer gaps.(1) Crab-like(2) Vela-likeChen & Ruderman 1993(3) ZC97 model(4) uniform(5) cosineNew modelDeath lines Zhang, L. et al. 2004, ApJ, 604, 317Cheng,K.S., Zhang et al. 2004, ApJ, 608, 418Pulsed X-ray luminosity
14、 of normal X-ray pulsarsX-ray LuminosityZhang & Jiang, 2005, A&AGamma-ray statistical propertiesZhang, Han, Jiang, 2005, A&A, 429, 489HE properties of High-field PulsarsZhang, Jiang, 2005, ApJ, 631High-filed:1013-1014 G 28 high-pulsar pulsars Zhang & Cheng, 1997, ApJ, 487,370Cheng & Zhang, 1998, ApJ
15、, 498,327脉冲星辐射的转换效率脉冲星辐射的转换效率 Return Zhang & Cheng, 1998, MNRAS, 294, 177Solid boxes: OursEmpty triangles: Harding,1981Empty diamonds: Dermer & Sturner 1994 X-X-射线脉冲星的辐射特性射线脉冲星的辐射特性 Return Cheng, Gil & Zhang, 1998, ApJ, 493, L35Cheng & Zhang 1999,ApJ,515,337 X-X-射线脉冲星的统计性质射线脉冲星的统计性质 Return Zhang & C
16、heng 1999,ApJ, 526, 327 射线射线脉冲星的统计特性脉冲星的统计特性 Return Cheng & Zhang 1998,ApJ,498,327 射线脉冲星产生的射线脉冲星产生的 射线对银河射线对银河 射线的贡献射线的贡献 Zhang & Cheng, 1998, MNRAS, 294,327ReturnReturn Comparison of observed e+/(e- + e+) ratio with predicted ones. The short-dashed curve is the ratio of positron background and tota
17、l electron background given by Moskalenko & Strong (1998). The solid, long dashed and dot-dashed curves are the ratios including the contribution of the mature gamma-ray pulsars with birth rates of one per 100 yrs, one per 50 yrs and one per 30 yrs respectively. (Zhang & Cheng, 2001, A&A)未证认的未证认的 射线
18、源与射线源与 射线脉冲星的关系射线脉冲星的关系 Solid lines:gamma-ray selection effectDashed lines: radio & gamma-ray selection effectsZhang & Cheng, 1998, A&A, 335, 234Zhang, Zhang & Cheng, 2000, 357, 957Return Phase-resolved and phase-averaged gamma-ray spectra of the Geminga pulsarEmission projection and pulseprofile fo
19、r Geminga parameter.Panel A: Photon emission from thepulsar as a function of phase.Panel B: Pulse profile. 3D structure of the outer gapsThe spectra of CrabZhang, Cheng, K.S. Mei, D.C. 2000, CPL, 17, 544Cheng, K.S. Ruderman, M. Zhang, L. 2000, ApJ,537,964 Emission projection onto the ( ,) plane and pulse profile. Panel A: photon emission;Panel B:radial distance vs. ; Panel C: pulse profile.The spectrum of PSR B1509-58Zhang & Cheng 2000,A&A, 363, 575
