On the Multiplicity of the O-Star Cyg OB2 #8a and its Contribution to the γ-ray Source 3EG J2033+4118

We present the results of an intensive spectroscopic campaign in the optical waveband revealing that Cyg OB2 #8A is an O6+O5.5 binary system with a period of about 21.9 days. Cyg OB2 #8A is a bright X-ray source, as well as a non-thermal radio emitter. We discuss the binarity of this star in the framework of a campaign devoted to the study of non-thermal emitters, from the radio waveband to γ-rays. In this context, we attribute the non-thermal radio emission from this star to a population of relativistic electrons, accelerated by the shock of the wind-wind collision. These relativistic electrons could also be responsible for a putative γ-ray emission through inverse Compton scattering of photospheric UV photons, thus contributing to the yet unidentified EGRET source 3EG J2033+4118. Based partly on data Obtained at the Observatoire de Haute-Provence, France.     

The nature of protons ejected from the nuclei of extragalactic radio sources

We have estimated the proton injection flux from the nuclei of some typical extragalactic radio sources (EGRS). To do so, we have used measured values of radio luminosities from these sources and have assumed the proton-proton collision model as a source of relativistic electrons which give rise to radio emission. The estimated values of the proton flux is in fairly good agreement with theoretical estimates of cosmic-ray fluxes within the same range of energy. This lends support to the fact that the nuclei of EGRSs might be the site for the generation of primary cosmic rays.     

Nonstationary radio luminosity of the remnant of Supernova 1181 (3C 58)

We measured the flux densities of the radio source 3C 58, which was identified with the remnant of SN 1181, in April–May 2003 relative to the spectrum of the standard source 3C 295 at fourf requencies in the range 1550 to 8450 MHz using the RTF-32 radio telescope at the Svetloe Observatory of the Institute of Applied Astronomy (Russian Academy of Sciences). We found significant nonstationary frequency-dependent flux-density variations in 3C 58 and variations in its instantaneous spectrum. We established that these variations occurred between 1986 and 1998. Based on data for the instantaneous spectra, we show that the break in the spectrum of 3C 58 results from prolonged energy losses by relativistic electrons through synchrotron radiation that took place in a nebula with an age of 5400 yr, equal to the age of the pulsar PSR J0205+6449. SN 1181 is shown to have exploded without the birth of a pulsar, which is characteristic of type-I supernovae. The shock acceleration of relativistic electrons after the explosion may be responsible for the observed nonstantionarity of the flux densities. The long-term evolution of the radio spectrum for the nebula 3C 58 and the nonstationary flux-density variations due to the explosion of SN 1181 are reconciled in terms of a model of an evolved binary system.     

Blazar天体射电爆发的持续注入喷流模型

为了解释Blazar天体射电爆发的普遍演化特性，本文提出一个持续注入的喷流模型．假定在喷流基底上以相对论性速度持续地注入相对记等离子体（由磁场和相对论电子组成）．这一等离子体在沿喷流向外运动时经受绝热膨胀损耗．理论计算表明，射电爆发的频谱演化具有Valtaoja等人所建议的典型的3阶段演化形式.它们非常好地重现了Blazar天体中观测到的射电爆发的普遍行为．     

The heating of the X-ray gas by the radiogas in the cluster PKS 0745-191

Calculations of the energy evolution of relativistic particles in a cluster of galaxies are presented. The heating of the X-ray gas by the radio gas in the cluster PKS 0745-191 is derived using Chandra X-ray data and VLA radio data. It is found that the heating is not sufficient for the radiation loss of the X-ray gas if the lower limit of energy in the power-law spectrum of relativistic electrons is set at 0.001 erg.     

Nonthermal radio emission from hot star winds

Nonthermal radio emission has been observed from some of the most luminous hot star winds. It is understood to be synchrotron radiation of the relativistic electrons in the winds. To understand how the electrons are accelerated to such high energies and to correctly explain the observed radio flux and spectra require an exhaustive investigation of all the relevant physical processes involved and possibly point to a complex wind structure. In this paper we discuss the logical path toward a comprehensive model of the nonthermal radio emission from hot star winds. Based on the available observational data and fundamental theoretical considerations, we found that the only physically viable and self-consistent scenario is:the nonthermal radio emission is synchrotron radiation of relativistic electrons the electrons are accelerated by shocks via the first-order Fermi mechanism the acceleration has to be in situ in the radio emitting region the shocks formed at the base of the winds have to propagate to beyond the radio photosphere).     

Cosmic-ray energetics in the supernova remnant Cassiopeia A

Based on the observed radio spectrum for the supernova remnant Cassiopeia A, we have established that it represents synchrotron radiation of relativistic electrons with a nonpower-law energy spectrum in the form of Kaplan-Tsytovich’s standard distribution. The total density of relativistic electrons is 10^?3 cm^?3, only 20% of which form the radio spectrum. The particle number ratio of the proton-nuclear and electron cosmicray components inside the shell differs significantly from the mean Galactic ratio (100) and probably does not exceed unity.     

Emission of Type II Radio Bursts – Single-Beam Versus Two-Beam Scenario

The foreshock region of a CME shock front, where shock accelerated electrons form a beam population in the otherwise quiescent plasma is generally assumed to be the source region of type II radio bursts. Nonlinear wave interaction of electrostatic waves excited by the beamed electrons are the prime candidates for the radio waves’ emission. To address the question whether a single, or two counterpropagating beam populations are a requirement for this process, we have conducted 2.5D particle-in-cell simulations using the fully relativistic ACRONYM code. Results show indications of three-wave interaction leading to electromagnetic emission at the fundamental and harmonic frequency for the two-beam case. For the single-beam case, no such signatures were detectable.     

Radio Emission of Flares and Coronal Mass Ejections

We review recent progress on our understanding of radio emission from solar flares and coronal mass ejections (CMEs) with emphasis on those aspects of the subject that help us address questions about energy release and its properties, the configuration of flare?–?CME source regions, coronal shocks, particle acceleration and transport, and the origin of solar energetic particle (SEP) events. Radio emission from electron beams can provide information about the electron acceleration process, the location of injection of electrons in the corona, and the properties of the ambient coronal structures. Mildly relativistic electrons gyrating in the magnetic fields of flaring loops produce radio emission via the gyrosynchrotron mechanism, which provides constraints on the magnetic field and the properties of energetic electrons. CME detection at radio wavelengths tracks the eruption from its early phase and reveals the participation of a multitude of loops of widely differing scale. Both flares and CMEs can ignite shock waves and radio observations offer the most robust tool to study them. The incorporation of radio data into the study of SEP events reveals that a clear-cut distinction between flare-related and CME-related SEP events is difficult to establish.     

The K-band luminosity function at z = 1: a powerful constraint on galaxy formation theory

We report the first detection of an inverse Compton X-ray emission, spatially correlated with a very steep spectrum radio source (VSSRS), 0038-096, without any detected optical counterpart, in cluster Abell 85. The ROSAT PSPC data and its multiscale wavelet analysis reveal a large-scale (linear diameter of the order of 500 h ⁻¹₅₀ kpc), diffuse X-ray component, in addition to the thermal bremsstrahlung, overlapping an equally large-scale VSSRS. The primeval 3 K background photons, scattering off the relativistic electrons, can produce the X-rays at the detected level. The inverse Compton flux is estimated to be (6.5 ± 0.5) × 10⁻¹³ erg s⁻¹ cm⁻² in the 0.5–2.4 keV X-ray band. A new 327-MHz radio map is presented for the cluster field. The synchrotron emission flux is estimated to be (6.6 ± 0.90) × 10⁻¹⁴ erg s⁻¹ cm⁻² in the 10–100 MHz radio band. The positive detection of both radio and X-ray emission from a common ensemble of relativistic electrons leads to an estimate of (0.95 ± 0.10) × 10⁻⁶ G for the cluster-scale magnetic field strength. The estimated field is free of the 'equipartition' conjecture, the distance, and the emission volume. Further, the radiative fluxes and the estimated magnetic field imply the presence of 'relic' (radiative lifetime ≳ 10⁹ yr) relativistic electrons with Lorentz factors γ ≈ 700–1700; this would be a significant source of radio emission in the hitherto unexplored frequency range ν ≈ 2–10 MHz.     

Circular Polarization and Magnetic Fields in Jet Models

The detection of circular polarization in compact synchrotron sources provides new insights into magnetic field configurations and the low-energy population of electrons in relativistic jets. Conversion of linear to circular polarization can be stimulated by Faraday rotation or turbulence in the source itself. A detailed model for the properties of the radio emission of Sgr A^* in the galactic center is presented.     

FAST Continuum Mapping of the SNR VRO 42.05.01

The relativistic electrons rotate in the enhanced magnetic field of the supernova remnants and emit the synchrotron radio emission.We aim to use the Five-hundre...     

Source models with electron diffusion

The general solution for the energy distribution of relativistic electrons in which electrons generated within the source diffuse and decay through synchrotron or Compton radiation is given for the case in which the magnetic field and the diffusion coefficient are constant. A very simple spherically symmetric model with an electron point-source at the centre is considered and the equations are explicitly solved. It is shown that notwithstanding its great simplicity this model gives a fair representation of the continuous emission of the Crab nebula from the radio to the X-ray region, with the simple assumption that it is due only to ordinary synchrotron radiation. If the central point source is identified with the pulsar there appears to be an upper limit of about 10⁷ MeV to the energy of the electrons accelerated by the pulsar mechanism.     

星系团PKS 0745-191中射电气体对X射线气体的加热

对星系团中相对论性粒子的能量演化做了数值计算，在此基础上，联合分析Chandra卫星数据和VLA射电观测结果，计算了星系团PKS0745-191中高能射电气体对X射线气体的加热作用，发现在射电气体幂律谱能量下限为0.001erg时，射电气体对X射线气体的加热不足以补充X射线气体的辐射能损．然后在计算研究了不同能量下限时射电气体对X射线气体的加热作用，并估计了射电气体的能量下限．     

Relationship between the nonstationary radio-luminosity variations of the Crab Nebula and the activity of its pulsar

Based on the half-century-long history of radio observations of the Crab Nebula, we investigate the evolution of its radio luminosity. We found a secular decrease in the radio luminosity; it has decreased by 9% since the discovery of the radio source in 1948. Apart from the secular decrease in the luminosity of the Crab Nebula, we identified two time intervals, 1981–1987 and 1992–1998, when radio bursts with energy release ～10⁴¹ erg took place. In these years, the spectral indices of the instantaneous spectra decreased significantly due to the increase in the flux densities at short (centimeter and millimeter) wavelengths. These events were preceded by sudden increases in the pulsar’s rotation rates, the largest of which, with an amplitude of ΔΩ/Ω = 3 × 10^?8, occurred in 1975 and 1989. We show that the magnetospheric instability mechanism that accompanies strong glitches can provide the energetics of the excess luminosity of the Nebula through the ejection of relativistic electrons with a total energy higher than 6 × 10⁴² erg from the pulsar’s magnetosphere.     

High Energetic Electrons Accelerated by a Coronal Shock Wave

Combined SOHO (Solar and Helisopheric Observatory) and ground based radio observations show evidently signatures of electrons accelerated by a shock wave during the event on July 9, 1996. A solar type II radio burst has been received as a signature of a coronal shock wave at 300 MHz on 9:10:54 UT. It was accompanied with electron beams appearing as type III radio bursts below 80 MHz. Simultaneously, the COSTEP (Comprehensive Suprathermal and Energetic Particle Analyzer) instrument aboard SOHO has measured enhanced electron fluxes in the range 30 keV – 3 MeV. This indicates that a coronal shock wave was able to produce high energetic electrons. A mechanism of electron acceleration up to relativistic velocities is presented and compared with the observations. The electron acceleration takes place at substructures of quasi-parallel collisionless shocks. This revised version was published online in July 2006 with corrections to the Cover Date.     

Coherent synchrotron emission observed: implications for radio astronomy

Synchrotron radiation by relativistic electrons spiralling in magnetic fields is a mainstay of radio astronomy, accounting for emissions from many objects. Conventional models assume that electrons radiate singly, so power scales with number of electrons. Yet recently jets from active galactic nuclei have shown very high luminosity, inconsistent with plausible single-particle synchrotron emission. We report experiments showing that, by stimulating plasma instabilities with relativistic electron beams, one can induce increases in the synchrotron emission by factors of ∼10⁶. Enhancement presumably arises from coherent bunching of the relativistic electrons as they spiral in an ambient magnetic field. Polarization measurements suggest that electrons radiatively cooperate on scales of ∼6.6 cm. Radio telescope Stokes parameters may be able to reveal such polarization effects in high-brightness sources, a new observing diagnostic.     

Coherent Synchrotron Radiation of Gamma-Ray Bursts

By now there is no doubt that the gamma-ray bursts (GRB) have a cosmological origin. This allows to regard GRB as the most powerful known energy sources, ε∼ 10⁵⁴ erg (with a total number of gamma quanta N_γ∼ 10⁶⁰). A plausible mechanism of coherent synchrotron radiation (CSR) of relativistic electrons driven by a local magnetic field is studied in this paper. We consider relativistic electrons arising in the Compton scattering of a GRB in directions close to that of the ray from the source to a ground-based observer. The synchrotron pulses from Compton electrons located at different points on the line between the GRB source and the observer arrive at the observation point simultaneously. This simultaneity ensures the coherence of the detected radiation. Both molecular clouds in the host galaxy of the GRB and our own Galaxy, as well as the Earth atmosphere are assumed to be scatterers of the GRB radiation. Signals of each scatterer reach the Earth surface, and can be detected at radio wavelengths. We estimate the characteristics of this radiation. The comparison of GRB data with the corresponding information on CSR pulses offers a way to determine some global characteristics of the medium between the Earth and the GRB source.     

Simulations of nonthermal electron transport in multidimensional flows: synthetic observations of radio galaxies

We have applied an effective numerical scheme for cosmic-ray transport to 3D MHD simulations of jet flow in radio galaxies (see the companion paper by Jones et al. herein). The marriage of relativistic particle and 3D magnetic field information allows us to construct a rich set of ‘synthetic observations’ of our simulated objects. The information is sufficient to calculate the ‘true’ synchrotron emissivity at a given frequency using explicit information about the relativistic electrons. This enables us to produce synchrotron surface-brightness maps, including polarization. Inverse-Compton X-ray surface-brightness maps may also be produced. First results intended to explore the connection between jet dynamics and electron transport in radio lobes are discussed. We infer lobe magnetic field values by comparison of synthetically observed X-ray and synchrotron fluxes, and find these ‘inverse-Compton’ fields to be quite consistent with the actual RMS field averaged over the lobe. The simplest minimum energy calculation from the synthetic observations also seems to agree with the actual simulated source properties.     

Cosmic Rays and Clusters of Galaxies

The presence of a significant population of relic relativistic electrons - created at an early epoch of the Universe - has been invoked to explain the diffuse EUV emission excess observed in a number of galaxy clusters. While the postulated inverse Compton scattering of the 3° K background radiation by cosmic ray electrons might indeed be utilized as an important diagnostic tool for the physical nature of the intracluster cosmic rays, it is shown here that continuous generation plus reacceleration would be necessary if the conditions on the observed energy spectral distribution and energy supply rate are to be met in the case of clusters with large radio halos. This revised version was published online in July 2006 with corrections to the Cover Date.