共查询到20条相似文献，搜索用时 125 毫秒
1.
利用三维脉冲星磁层模型研究了磁层外隙的几何结构,首先用自治模型确定“外隙”的垂直尺度,在该模型中外隙尺度受回流的外隙流（带有隙加速的带电粒子发射的曲率光子）加热极帽而产生的热光子的碰撞而成对生成所限,外隙的横向尺度也受本地对生成所限,在脉冲星的磁层中,原则上有两个拓扑分离的外隙,允许同时进入和流出粒子,不过,流入粒子流产生的辐射形态受隙了本地对生成和恒星附近的磁对生成的严格制约,根据外隙及其本地结构的三维模型计算了类Crab脉冲星的辐射和相位分解谱。 相似文献
2.
脉冲星ＰＳＲ１９５１＋３２的Ｘ射线脉冲辐射程凌翔，李惕碚，孙学军，马宇蒨，吴枚（中国科学院高能物理研究所，北京１０００３９）主题词：脉冲星－Ｘ射线源１９８７年６月，用频率３８７ＭＨｚ的射电观测发现了脉冲星ＰＳＲ１９５１＋３２［１］，同年７月，在１８０... 相似文献
3.
4.
反常X射线脉冲星的研究进展 总被引：1，自引：0，他引：1
反常X射线脉冲星（Anomalous X-ra Pulsars，简称AXP）是一类特殊的X射线源。与X射线脉冲星（通常处于大质量X射线双星系统中）相比，它们具有以下特征：X射线谱较软、光度低页稳定（≈10^27－10^29J.s^-1）、自转周期集中在10s左右稳定增长、迄今没有找到它们的光学、红外、射电的对应体、有一些可能戌超新星遗迹成协等。由观测到的自转周期变化可以确定它们的自转能损不足以提供有X射线辐射。解释AXP能源机制的理论模型目前主要有两大类：在吸积模型中，AXP被认为具有正常磁场强度（≈10^8T）的中子量，物质吸积提供X射线辐射原能源，并造成中子星的自转变化；另一种观点认为AXP是具有超强磁场（≈10^10-10^11T）的中子量（即磁星），其辐射能源来自它们巨大的磁或残余的热能，观测到的自转周期及其变化被归因子中子星的磁偶极辐射和物质抛射。两种模型各有优缺点，但目前看来观测事实对磁星模型较为有利。为了进一步明确AXP的性质，提供解释它们能源机制的线索，在介绍AXP的基本观测特征和理论解释的基础上，还将AXP与射电脉冲星、特强磁场射电脉冲量、射电宁静脉冲星侯选体及软γ射线复现源分别进行了比较。 相似文献
5.
评述了射电脉冲星搜寻及观测研究的巨大贡献和重要意义，分析了影响脉冲星搜寻工作的几个关键因素（如灵敏度，色散，观测频率及设备等），着重介绍和分析了自发现脉冲星（特别是发现第一颗秒脉冲星）以来所进行的卓有成效的脉冲星搜寻工作（包括脉冲星的早期寻，毫秒脉冲星的初期搜寻，高银续脉冲星搜寻，定向搜寻以及进一步的广域深空搜寻等）的情况，结果，意义和进展。 相似文献
6.
本文分析γ射线脉冲星最近的观测数据，研究各波段辐射位相的一些关联，它们对于揭示γ射线脉冲星的辐射机制可能有重要的意义， 相似文献
7.
8.
脉冲星的偏振信息是理解脉冲星辐射区的重要手段，利用澳大利亚的64m射电望远镜进行大量的脉冲星观测，得到了一批脉冲星的偏振轮廓和偏振参数，编辑了几乎所有发表的脉冲星轮廓资料，系统总结了脉冲星圆偏辐射的规律，为理论上解释脉冲星辐射这一重要难题提供观测依据和物理限制，利用脉冲星作为探针，研究了银河系磁场结构和模型，确定了银河系BS磁场模型，发现了银河系上下反对称的环向磁场，并首次对星系尺度的发电机类型进行判别，证认出A0型发电机运行于银河系，发现了银晕中的垂直磁场和M31及银盘中的非常延展的磁场，探测到NGC2997星系中由内到外的旋涡磁场，并提出可能有两种发电机在这个星系的不同区域运行。 相似文献
9.
脉冲宽度的测量方法有几种.最常用的脉冲宽度有Wpp（两峰值点的间距）、W50（最高峰值强度50%处的宽度）和W10（最高峰值强度10%处的宽度）.另外,还有测量两个最外成分各自强度50%处的宽度Wc50和各自强度10%处的宽度Wc10.利用16颗双锥峰脉冲星和7颗核锥三峰脉冲星样本在1.4 GHz的脉冲轮廓数据,测量了5种脉冲宽度.利用有磁倾角α和撞击角β数据的脉冲星,导出了对应的辐射束半径ρ,并验证其与脉冲星周期P之间的关系ρ∝P-0.5.通过比较5种脉冲宽度导出的ρ与P关系的好坏,发现最外成分之间的宽度比前面3种宽度更好,其中Wc50宽度得出的相关关系最好.由此认为Wc50是最能反映辐射束宽度的测量值.还讨论了脉冲轮廓的对称性,发现后随的锥辐射成分与先导的锥辐射成分相比,更靠近核心辐射成分,两个锥辐射成分的宽度在统计上基本相同. 相似文献
10.
11.
Unified classical and quantum radiation mechanism for ultrarelativistic electrons in curved and inhomogeneous magnetic fields 总被引：1，自引：0，他引：1
We analyse the general radiation emission mechanism from a charged particle moving in a curved inhomogeneous magnetic field. The consideration of the gradient makes the vacuum magnetic field compatible with the Maxwell equations, and adds a non-trivial term to the transverse drift velocity, and, consequently, to the general radiation spectrum. To obtain the radiation spectrum in the classical domain a general expression for the spectral distribution and characteristic frequency of an electron in arbitrary motion is derived, by using Schwinger's method. The radiation patterns of the ultrarelativistic electron are represented in terms of the acceleration of the particle. The same results can be obtained by considering that the motion of the electron can be formally described as an evolution caused by magnetic and electric forces. By defining an effective electromagnetic field, which combines the magnetic field with the fictitious electric field associated to the curvature and drift motion, one can obtain all the physical characteristics of the radiation by replacing the constant magnetic field with the effective field. The power, angular distribution and spectral distribution of all three components (synchrotron, curvature and gradient) of the radiation are considered, in both the classical and the quantum domain, within the framework of this unified formalism. In the quantum domain the proposed approach allows the study of the effects of the inhomogeneities and curvature of the magnetic field on the radiative transition rates of electrons between low-lying Landau levels and the ground state. 相似文献
12.
Jiong Liu Ye-Fei Yuan Xiao-Long Deng Center for Astrophysics University of Science Technology of China Hefei 《中国天文和天体物理学报》2007,7(2):304-316
Synchro-curvature radiation describes the emission from a relativistic charged par- ticle which is moving and spiralling in a curved magnetic field. We investigate the maser emission for synchro-curvature radiation including drift of the guiding center of the radiating electron. It is shown that under some conditions the absorption coefficient can be negative, so maser can happen. These conditions are different from those needed for maser emission of curvature radiation including drift of the charged particles. We point out that our results, in- cluding the emissivity, can reduce to these of curvature radiation. Previously it was found that synchro-curvature radiation can not generate maser in vacuum, but we argue that synchro- curvature radiation including drift can generate maser even in vacuum. We discuss the possi- bilities of the potential applications of the synchro-curvature maser in modeling gamma ray bursts and pulsars. 相似文献
13.
The puzzling mechanism of coherent radio emission remains unknown, but fortunately, repeating fast radio bursts (FRBs) provide a precious opportunity, with extremely bright subpulses created in a clear and vacuum-like pulsar magnetosphere. FRBs are millisecond-duration signals that are highly dispersed at distant galaxies but with uncertain physical origin(s). Coherent curvature radiation by bunches has already been proposed for repeating FRBs. The charged particles are created during central star's quakes, which can form bunches streaming out along curved magnetic field lines, so as to trigger FRBs. The nature of narrow-band radiation with time-frequency drifting can be a natural consequence that bunches could be observed at different times with different curvatures. Additionally, high linear-polarization can be seen if the line of sight is confined to the beam angle, whereas the emission could be highly circular-polarized if off-beam. It is also discussed that pulsar surface may be full of small hills (i.e., zits) which would help producing bulk of energetic bunches for repeating FRBs as well as for rotation-powered pulsars. 相似文献
14.
We test a new emission mechanism in pulsar magnetospheres, eventually responsible in part for the high level of observed radio radiation. This is carried out by comparing the efficiency of the two-stream instability of Langmuir waves in a pulsar emission region, where the stationary and non-stationary characters of pair plasma outflows produced in the gap region are characterized by two different time-scales. On the shorter time-scale, the Ruderman &38; Sutherland 'sparking' phenomenon leads to the creation of pair plasma clouds, in motion along magnetic field lines, that contain particles with a large spectrum of momenta. The overlapping of particles with different energies produced in successive clouds results in an efficient 'two stream'-like instability. This effect is a consequence of the non-stationary character of the pair plasma produced in the gap region, just above the magnetic poles of the neutron star. On a long time-scale, resulting pair plasma outflows in pulsar magnetospheres can be treated as stationary. In this case, the instability which results from interaction between existing primary beam particles and the pair plasma is negligible, whereas the instability owing to interaction between electrons and positrons of the pair plasma itself, and more precisely to their relative drift motion along curved magnetic field lines, is effective. We derive characteristic features of the triggered instability, using specific distribution functions to describe either particles in the assembly of clouds or relative drifting of electrons and positrons in these same plasma clouds. Although linear and local, our treatment suggests that non-stationary effects may compete with, or even dominate over, drifting effects in parts of pulsar emission regions. 相似文献
15.
N. A. Silant’ev Yu. N. Gnedin S. D. Buliga M. Yu. Piotrovich T. M. Natsvlishvili 《Astrophysical Bulletin》2013,68(1):14-25
Estimates of magnetic fields for a number of active galactic nuclei are presented. These estimates are based on the observed polarization degrees and position angles of broad Hα lines and in the nearby continuum and on asymptotic analytical formulas for the Stokes parameters of the radiation emerging from a magnetized accretion disk (the Milne problem in a magnetized atmosphere). The characteristic observed feature of the wavelength dependence of the polarization degree inside the line—a minimum at the center and a fast increase of the position angle from one wing to another—can be explained by the superposition of resonance emission from two or more clouds located in the right (Keplerian velocity directed away from the observer) and left (Keplerian velocity directed toward the observer) parts of the orbit in the rotating magnetized accretion disk. The main component in our mechanism is the azimuthal magnetic field in the disk. The presence of a magnetic field perpendicular to the disk plane (which is usually weaker than the azimuthal field) results in the asymmetry of the distribution of the polarization degree and position angle inside the line. The inferred magnetic field strengths at the galactocentric distances where broad lines are emitted can be used to estimate the magnetic fields in the region of the centermost stable orbit and at the horizon of the central black hole, using the power-law dependence of the magnetic field strength corresponding to the standard model of the accretion disk. 相似文献
16.
Liu Dang-bo Huang Yong-fengDanzeng Luo-bu Chen Tian-lu 《Chinese Astronomy and Astrophysics》2011,35(3):227
The resonant inverse Compton scattering (RICS) of relativistic electrons in intense magnetic fields is an efficient mechanism for producing the highenergy γ-rays. In our previous work it is suggested that the early-stage γ-ray radiation of γ-ray bursts (GRBs) may be mainly produced by this mechanism. By using this mechanism, some puzzles in the study of GRBs can be clarified, e.g., the origin of the Amati relation obtained from the statistics of observations, the formation of the observed two-segment (broken) power-law spectra, the relevant “deadline problem”, the polarization property, etc. Herein our discussion will be focused on the formation of the broken power-law spectra. Based on the formula of the RICS spectral power of individual fast electrons, we have derived the simplified analytical formula of the collective RICS radiation spectrum (RICS spectral luminosity) produced by the assembly of relativistic electrons in an intense magnetic field when they pass through the ambient low-frequency radiation field, and applied it to several typical low-frequency radiation fields (e.g., the black-body radiation field, power-law radiation field and thermal bremsstrahlung field) around the central neutron star, for the convenience of comparison with the observed spectra. Our calculations indicate that the RICS radiation mechanism has a very high efficiency in the hard X-ray and γ-ray wavebands, if the matching condition (i.e., the condition approximate to resonance) is satisfied, and that independent of the ambient radiation field, the produced spectra are commonly the two-segment power-law spectra. Additionally, it is suggested that the RICS mechanism might be an ideal highly-efficient radiation mechanism for the high-energy emissions (hard X-rays and γ-rays) of the GRBs, soft γ-ray repeated bursts (SGRs) and γ-ray pulsars (GRPs). 相似文献
17.
Yu. N. Mishurov I. A. Acharova M. G. Shevchenko D. A. Tyshlangov 《Astrophysical Bulletin》2014,69(1):21-26
A new mechanism of sweeping out of dust grains beyond galactic disks both in the radial direction along the galactic plane and in the vertical, cross-disk direction is proposed. The mechanism is driven by the interaction of dust grains with the bisymmetric nonstationary magnetic field of the galaxy, whose lines are curved and corotate with the stellar spiral density wave responsible for the arms. We attribute the radial transfer of interstellar dust grains in the plane of galactic disks to the fact that charged dust grains are “glued” to magnetic field lines and are therefore pushed outward because of the rotation of magnetic field lines and their tilt with respect to the radial direction parallel to the disk plane. In addition, dust is swept out vertically in the cross-disk direction because of the drift motion in crossed magnetic and gravitational fields (both are parallel to the galactic plane). Numerical computations of the motion of dust grains in real magneto-gravitational fields with the allowance for the drag force from interstellar gas show that the time scale of dust grain transport beyond galactic disks is on the order of 1 Gyr or shorter. 相似文献
18.
Dipanjan Mitra 《Journal of Astrophysics and Astronomy》2017,38(3):52
The pulsar radio emission originates from regions below 10% of the light cylinder radius. This requires a mechanism where coherent emission is excited in relativistic pair plasma with frequency \(\nu _{\mathrm{cr}}\) which is below the plasma frequency \(\nu _{\circ }\) i.e. \(\nu _{\mathrm{cr}} < \nu _{\circ }\). A possible model for the emission mechanism is charged bunches (charged solitons) moving relativistically along the curved open dipolar magnetic field lines capable of exciting coherent curvature radio emission. In this article, we review the results from high quality observations in conjunction with theoretical models to unravel the nature of coherent curvature radio emission in pulsars. 相似文献
19.
R. T. Gangadhara 《Astrophysics and Space Science》1995,232(2):327-336
Pulsars accelerate the charged particles moving along their magnetic field lines due to their rapidly spinning motion. Particles gain maximum energy from pulsars within the light cylinder when they are moving along the field lines perpendicular to the rotation velocity. In pulsars with non-aligned rotation and magnetic axes, the production of two intense and sharp pulses (main pulse and interpulse) separated by 180° longitude occur at the two regions near the light cylinder where the rotation velocity is perpendicular to the magnetic field. Since the radiating particles move radially along the relativistically compressed magnetic field lines, the observer in the stationary frame receives beamed and transversely compressed radiation pulse. Near the light cylinder position angle varies smoothly during pulsar rotation in a way as Radhakrishnan and Cook (1969) expect its variation near the magnetic pole, as the field lines experience relativistic compression in the direction of rotation. The motion of two charge species along the field lines produce orthogonal modes at each pulse longitude. 相似文献
20.
E. V. Derishev F. A. Aharonian V. V. Kocharovsky Vl. V. Kocharovsky 《Astrophysics and Space Science》2005,297(1-4):21-30
We discuss the properties of gamma-ray radiation accompanying the acceleration of cosmic rays via the converter mechanism.
The mechanism exploits multiple photon-induced conversions of high-energy particles from charged into neutral state (namely,
protons to neutrons and electrons to photons) and back. Because a particle in the neutral state can freely cross the magnetic
field lines, this allows to avoid both particle losses downstream and reduction in the energy gain factor, which normally
takes place due to highly collimated distribution of accelerated particles. The converter mechanism efficiently operates in
relativistic outflows under the conditions typical for Active Galactic Nuclei, Gamma-Ray Bursts, and microquasars, where it
outperforms the standard diffusive shock acceleration.
The accompanying radiation has a number of distinctive features, such as an increase of the maximum energy of synchrotron
photons and peculiar radiation beam-pattern, whose opening angle is much wider at larger photon energies. This provides an
opportunity to observe off-axis relativistic jets in GeV–TeV energy range. One of the implications is the possibility to explain
high-latitude unidentified EGRET sources as off-axis but otherwise typical relativistic-jet sources, such as blazars. 相似文献