共查询到20条相似文献，搜索用时 599 毫秒
1.
Ｓｙｎｃｈｒｏ－ＣｕｒｖａｔｕｒｅＲａｄｉａｔｉｏｎ──弯曲磁场中一种新的、更普遍的辐射张家铝（中国科技大学天体物理中心合肥２３００２６）郑广生（香港大学物理系）关键词同步辐射，曲率辐射，脉冲星磁层在脉冲星的辐射模型中，同步辐射和曲率辐射占有极其重要... 相似文献
2.
耀变体(blazar)的X射线辐射位于同步辐射的尾部及逆康普顿辐射的前部分,因此其辐射起源较为复杂.耀变体从射电到X射线波段辐射的谱能分布(SED)可用抛物线函数近似拟合.若将该拟合所得拟合曲线近似视为耀变体的物理谱,分析费米(Fermi)耀变体的X射线辐射,则结果表明:耀变体的X射线辐射包含同步辐射和逆康普顿辐射2个成份,并可用该拟合线将X射线的同步辐射和逆康普顿辐射成份进行简单分离;源的同步峰频越高,其同步辐射成份越多,而其逆康普顿辐射成份越少;在X射线1 keV处,对于平谱射电类星体(FSRQ)、低同步峰BL Lac天体(LBL)和高同步峰BL Lac天体(HBL),其同步辐射成份占总辐射的比例分别为17%、27%和73%;同步峰频与X射线1 keV处同步辐射流量密度有强正相关,而与逆康普顿辐射流量密度无相关;在X射线波段,LBL的辐射机制与FSRQ的类似. 相似文献
3.
本文讨论了一类适用于描述中性片过程的非均匀磁场中的电子运动和辐射,预言了沿中性片飞出粒子动量的可能的量子化,给出了这类非均匀磁场中同步辐射和回旋辐射的角谱分布,并和均匀磁场情况作了比较。 相似文献
4.
γ射线暴的研究进展（Ⅱ）：γ暴的辐射机制及能谱形成 总被引：1，自引：0，他引：1
在中子星作为γ暴源的基础上讨论了各种辐射机制及能谱形成。由于中子星表面磁场很强，我们首先讨论了强磁场中的辐射过程，包括同步辐射和吸收，单光子和双光子的产生和湮灭，康普顿散射，轫致辐射等。 相似文献
5.
研究了等离子体反应堆模型,统一解释活动星系核的辐射性质,特别是ＢＬＬａｃ天体的谱性质．具体的物理过程是:大量相对论电子从中心天体注入周围的等离子体反应堆中,通过同步辐射快速损失能量,同时这些电子同步吸收反应堆中不透明的光子,产生一个稳定、各向同性的幂律分布,其谱指数为γ＝３;然后,这些相对论电子通过等离子体反应堆的爆发或其表面扩散过程逃逸出来,产生低频的同步辐射;来自等离子体反应堆的高频辐射表现出快速的谱变化,即流量减小时谱变陡．另外,还详细分析了具有辐射损失和相对论电子注入的同步辐射源的性质． 相似文献
6.
李宏为 《中国天文和天体物理学报》1989,(3)
本文提出具幂津谱分布的非热电子在多重偶极子磁场中产生回旋同步辐射是晚型恒星宁静微波辐射的一个可能机制。文中假设有10—20个磁偶极子随机地分布在恒星光球之下,非热电子与背景热电子数密度之比<10~(-3),并且在非热电子分布中引入了与其寿命有联系的因子。由此计算并分析了回旋同步辐射谱和偏振性质,并获得了辐射源的空间分布特性。 相似文献
7.
γ射线暴是宇宙中恒星尺度的最剧烈爆发现象。γ射线暴瞬时辐射结束后,进入余辉辐射阶段。X射线耀发是γ射线暴X射线辐射衰减过程中出现的短时标闪耀现象。X射线耀发的脉冲轮廓具有不对称性,其上升时标小于下降时标。在部分γ射线暴中,X射线耀发的亮度达到瞬时辐射的亮度。X射线耀发的持续时间与峰值时间具有线性关系。X射线耀发的光谱比X射线余辉的光谱硬。早期X射线耀发与晚期X射线耀发相比,其脉冲轮廓较窄,光谱较硬。X射线耀发产生的物理过程类似于γ射线暴瞬时辐射的物理过程。在火球(fireball)模型中,内部壳层之间发生碰撞,产生的内激波加速电子,电子的同步辐射产生X射线耀发。当火球扫过星际介质,外激波加速电子时,电子的同步辐射也可产生X射线耀发。在光球(photospere)模型中,能量耗散发生在光学厚的区域,热辐射的光谱峰值落在X射线能段附近,γ射线暴的喷流在光球半径处会产生X射线耀发。如果射线暴喷流由坡印亭能流主导,喷流就会与星际介质相互作用,磁场的不稳定性使磁场发生耗散,产生的能量形成X射线耀发。γ射线暴的喷流具有几何效应。一部分同步辐射可能发生在喷流辐射面的高纬度处。由于曲率效应(curvature effect),各向异性辐射与各向同性辐射相比,X射线耀发的峰值出现较晚。此外,在γ射线暴发生后,黑洞会间歇性地吸积外部介质。在吸积过程中,黑洞周围的磁场会调节吸积的速率和喷流中的能量,这是出现多个X射线耀发的原因。 相似文献
8.
由分析可知，在光学厚的介质中麦氏分布的极端相对论电子在磁场中能产生同步加速辐射，其辐射谱为瑞利—金斯谱．基于Fokker-Planck方程，这种波场对快电子的加速将产生幂律分布的电子能谱．考虑到日冕活动区的物理条件，在太阳耀斑中观测到的10Mev左右的电子能谱很可能就是由同步加速辐射加速快电子产生的． 相似文献
9.
10.
本文对相对论电子的辐射性质、能谱演化和加速机制等进行了简要的介绍。同时，对相对论电子在高能天体中的辐射作用和特性进行了简要的综述。本文给出了相对论电子在Blazar天体的射电辐射机制、光变机制、BL Lac天体的辐射机制以及γ暴的辐射机制等方面的应用研究成果。1、提出了相对论电子的光学薄同步辐射模型：解释Blazar天体的射电平谱：Blazar中心体的剧烈活动，使射电辐射区处于等离子体湍动状态，其中的相对论电子在湍动等离子体波的二交费米加速、激波加速、辐射损失、粒子逃逸和辐射区的绝热减速等物理过程作用下，形成较平的能谱，产生射电平谱。2、提出了新的Blazar天体光变模型：当Blazar天体爆发时，中心天体产生大量的相对论电子，注入喷流中；相对论电子产生同步辐射，并不断损失能量和逃逸辐射区，使它们的能谱快速变化，引起辐射发生快速光变。3、给出了BL Lac天体的等离子体反应堆模型：大量相对论电子从中心天体注入周围的等离子体反应堆中，通过同步辐射快速损失能量，同时这些电子同步吸收反应堆中不透明的光子，产生一个稳定、各向同性的幂律分布，其谱指数为γ＝3；然后，这些相对论电子通过等离子体反应堆的爆发或其表面扩散过程逃逸出来，辐射低频的同步辐射。模型解释了BL Lac天体的高频辐射表现出快速的谱变化性质，即流量减小时谱变陡。4、提出了相对论电子的内激波加速模型，解释γ暴的尖峰光变特性：在γ暴产生的相对论运动的壳层中，有内激波产生；激波在壳层中传播，耗散壳层的运动能，使其中的部分电子加速成为相对论电子。然后，这些电子通过同步辐射产生观测到的γ辐射。模型认为，γ暴中的每个尖峰辐射是一对内激波加速相对论电子的辐射过程，复杂的γ暴光变曲线是多对内激波辐射过程的叠加。 相似文献
11.
The changes in the high-energy gamma-ray spectra due to electron-photon cascading in the photon field (e.g., microwave background radiation) are investigated.The propagation of gamma-rays with an initial power-law spectrum through an isotropic monoenergetic photon field is considered. Two processes of the cascade particle-photon field interaction are taken into account, namely, the photoproduction of electron-positron pairs and the inverse Compton effect. The effect of the synchrotron energy loss by cascade electrons in a magnetic field on the cascade gamma-quantum spectrum is studied. The results may be used to estimate the absorption and the variations in the shape of the spectrum of radiation from compact gamma-ray sources in the metagalaxy.The cascade characteristics have been obtained by numerically solving the cascade equations by the moment method. 相似文献
12.
We present a model which describes the evolution of the energy spectrum of relativistic electrons in supernova remnants, with radiation losses of electrons taken into account. The model can be used to calculate the synchrotron X-ray emission from supernova remnants in the uniform interstellar medium and in the uniform interstellar magnetic field. The importance of various factors in the variations of spatial distributions of nonthermal electrons and their synchrotron emissive capacity is demonstrated. We analyze the errors which arise in the magnetic field strength when it is estimated with the use of the models which ignore the detailed pattern of the evolution of the magnetic field and the electron spectrum behind the shock front in the remnant. The evolution of synchrotron emission spectrum and the ratio between the synchrotron radio and X-ray fluxes from supernova remnants are calculated. 相似文献
13.
Acceleration of Electrons and Protons in Reconnecting Current Sheets Including Single or Multiple X-points 总被引：1，自引：0，他引：1
Kinematic characteristics of electrons and protons in the magnetic reconnecting current sheet in the presence of a guide field are investigated. Particle trajectories are calculated for different values of the guide field by a test-particle calculation. The relationship between the final energy and the initial position has also been studied. We found that the addition of a guide field not only allows particles to get more energy and not only results in the separation of electrons and protons, but also causes the reconnecting electric field to selectively accelerate electrons and protons for different initial positions. The energy spectrum eventually obtained is the common power-law spectrum, and as the guide field increases, the index for the spectrum of electrons decreases rapidly. However, for a weak background magnetic field, proton spectra are not very sensitive to the guide field; but for a strong background field, the dependence of the spectrum index is similar to the electron spectrum. Meanwhile, kinematic characteristics of the accelerated particles in the current sheet including multiple X-points and O-points were also investigated. The result indicates that the existence of the multiple X- and O-points helps particles trapped in the accelerating region to gain more energy, and yields the double or multiple power-law feature. 相似文献
14.
It is generally believed that the synchrotron radiation of electrons from the internal shock is the main radiation mechanism of the prompt GRB (gamma-ray burst) emission. However, what this model predicts can not explain observations well. In this paper, we confirm that electrons are quickly cooled due to radiation losses and also point out that the synchrotron radiation spectrum presented in previous papers is a relatively rough estimation. We get the precise synchrotron radiation spectrum of fast-cooling electrons by carrying out a numerical calculation, and thereby reasonably explain the observed distribution of low-energy spectral index (α) of long GRBs based on a unified model. In addition, we fit the correlation between α and the peak energy of the νFν spectrum (Ep). 相似文献
15.
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
16.
Magnetized accretion flows around black holes which include standing or oscillating shock waves can produce very realistic
spectrum till a few MeV. These shocks accelerate hot electrons which produce power-law spectrum. The post-shock region intercepts
soft-photons from an external source, namely, a Keplerian disk and also from distributed sources such as the synchrotron photons
emitted from thermal and non-thermal electrons originated in the pre-shock and post-shock flow. These photons are inverse
Comptonized by the thermal and the non-thermal electrons present in the CENBOL region. Computations show that the emitted
radiation is extended till a few MeV. We include the bulk motion Comptonization as well and discuss its importance vis-a-vis
the power-law spectrum produced by non-thermal electrons.
相似文献
17.
Li-Hong Yan Jian-Cheng Wang Yunnan Observatory /National Astronomical Observatories Key Laboratory for the Structure Evolution of Celestial Objects Chinese Academy of Sciences Kunming China Graduate School of Chinese Academy of Sciences Beijing China 《中国天文和天体物理学报》2011,(6)
We present a new explanation for the origin of the steep power-law(SPL) state of X-ray binaries.The power-law component of X-ray emission is the synchrotron radiation of relativistic electrons in highly magnetized compact spots orbiting near the inner stable circular orbit of a black hole.It has a hard spectrum that extends to above MeV energies,which is determined by the electron acceleration rate.These photons are then down-scattered by the surrounding plasma to form an observed steep spectrum.We discuss ... 相似文献
18.
通过采用试验粒子的方法,研究了在有引导磁场Bz存在的磁重联电流片中,电子被super-Dreicer电场Ez加速后的运动特征.首先,考虑了引导磁场恒定且与电场有不同方向时对粒子加速的影响.在这种情况下,Bz方向的改变直接改变了电子的运动轨迹,使其沿着不同的路径离开电流片.在Bz和Ez同向时,高能电子的pitch-angle接近于180°.然而,当2者反向时,高能电子的pitch-angle接近0°.引导磁场的取向只是使电场有选择地对不同区域的电子进行加速,不会最终影响电子的能量分布,最终得到的能谱是普遍的幂率谱E-γ.在典型的日冕条件下, γ大约等于2.9.进一步的研究表明γ的大小依赖于引导磁场及磁重联电场的强弱,以及电流片的尺度.随后,也研究了包含多个X-点和O-点电流片中被加速粒子的运动特征.结果表明X-点和O-点的存在使得粒子被束缚在加速区并获得最大的加速,而且最终的能谱具有多幂率谱的特征. 相似文献
19.
Grzegorz Wardzi&#;ski Andrzej A. Zdziarski 《Monthly notices of the Royal Astronomical Society》2000,314(1):183-198
We investigate the process of synchrotron radiation from thermal electrons at semirelativistic and relativistic temperatures. We find an analytic expression for the emission coefficient for random magnetic fields with an accuracy significantly higher than those derived previously. We also present analytic approximations to the synchrotron turnover frequency, treat Comptonization of self-absorbed synchrotron radiation, and give simple expressions for the spectral shape and the emitted power. We also consider modifications of the above results by bremsstrahlung.
We then study the importance of Comptonization of thermal synchrotron radiation in compact X-ray sources. We first consider emission from hot accretion flows and active coronae above optically thick accretion discs in black hole binaries and active galactic nuclei (AGNs). We find that for plausible values of the magnetic field strength, this radiative process is negligible in luminous sources, except for those with hardest X-ray spectra and stellar masses. Increasing the black hole mass results in a further reduction of the maximum Eddington ratio from this process. Then, X-ray spectra of intermediate-luminosity sources, e.g. low-luminosity AGNs, can be explained by synchrotron Comptonization only if they come from hot accretion flows, and X-ray spectra of very weak sources are always dominated by bremsstrahlung. On the other hand, synchrotron Comptonization can account for power-law X-ray spectra observed in the low states of sources around weakly magnetized neutron stars. 相似文献
We then study the importance of Comptonization of thermal synchrotron radiation in compact X-ray sources. We first consider emission from hot accretion flows and active coronae above optically thick accretion discs in black hole binaries and active galactic nuclei (AGNs). We find that for plausible values of the magnetic field strength, this radiative process is negligible in luminous sources, except for those with hardest X-ray spectra and stellar masses. Increasing the black hole mass results in a further reduction of the maximum Eddington ratio from this process. Then, X-ray spectra of intermediate-luminosity sources, e.g. low-luminosity AGNs, can be explained by synchrotron Comptonization only if they come from hot accretion flows, and X-ray spectra of very weak sources are always dominated by bremsstrahlung. On the other hand, synchrotron Comptonization can account for power-law X-ray spectra observed in the low states of sources around weakly magnetized neutron stars. 相似文献
20.
We survey the observational data on infrared, optical and X-radiation sources associated with energetic cosmic events, and note the occurrence of an apparently preferred value of the spectral index,n=1, for the radiation continua. We review the essentials of standard synchrotron radiation theory; the conventional interpretation of the observational data in terms of an energy distribution of electrons injected into a constant, low valued magnetic field; and the somewhat unsatisfactory attempts that can be made to explain this electron energy distribution in terms of the Fermi acceleration mechanism. We examine the evidence for the presence in the radiation sources of high magnetic fields, which cause evolution of the synchrotron radiation power spectrum to occur. We work out the consequences of this evolution, and obtain a new form of synchrotron radiation theory, which we describe astime-integrated synchrotron radiation theory, the particular advantage of which is that it is able to give a unique value (n=1/2 of the spectral index for radiation produced by a single high energy electron, independently of the initial electron energy. We consider the consequences of there being a distribution of magnetic field values in a radiation source; and in particular we consider a uniform distribution (in which all values are equally probable), which is capable of producing the required spectral indexn=1. We show that this uniform distribution can be explained in terms of a model in which there exist condensations of material containing high magnetic fields and within which electrons can be generatedin situ, through the familiar pion production and decay processes. We also consider systems in which electrons in a radiation source have injection patterns that enable the radiation continua to be interpreted in terms of time-integrated synchrotron radiation theory, originally devised for a single electron. We apply these considerations to sources of optical and higher frequency radiation; we also show that they have limited application to certain types of radio source. We suggest in conclusion that the condensations that feature in our model could act as basic units of structure for complex radiation sources associated with different types of energetic cosmic event, and that therein could lie the clue to the evident similarity of their radiation continua. 相似文献