强磁场中相对论电子系集体的共振逆康普顿散射谱

强磁场中相对论电子的共振逆康普顿散射(RICS)是产生伽玛射线的有效机制.以前的工作曾论证,伽玛暴(GRB)的早期伽玛射线辐射可能主要由该机制产生.利用此辐射机制,伽玛暴研究中的一些困惑有可能得到较好的解释.例如,观测统计给出的"Amati关系"的起源,两段式(折断式)幂律谱的形成,特别是其中"死线问题"的解决方案,还有偏振的存在等.这里将重点讨论折断幂律谱形成问题.基于单个电子的RICS谱功率公式,导出了强磁场中大量相对论电子穿过周边低频辐射场时产生的集体RICS辐射谱(RICS谱光度)的简化解析公式,并将它应用于中子星周边几种典型的低频场(如黑体辐射场、幂律辐射场以及热轫致辐射场),以便与实际观测谱形比较.计算表明:在满足匹配条件(即近似共振条件)下,RICS辐射效率很高,其谱形普遍为两段式的幂律谱形式,与周边低频场性质无关.还论证RICS机制可能是伽玛暴、软伽玛重复暴和伽玛射线脉冲星在高能射线波段(硬X射线和伽玛射线)的一个理想的高效辐射机制.     

变化磁场中相对论电子系集体的共振逆康普顿散射谱

强磁场中的共振逆康普顿散射(RICS)是产生伽玛射线的有效机制．在前文工作的基础上，导出强磁场中子星中具有幂律能谱的大量相对论电子沿中子星磁轴向外运动时在变化磁场中产生的集体RICS辐射谱(RICS谱光度)的基本公式．由此得到在中子星周边几种典型的低频辐射场中集体RICS辐射谱形的简单解析表示(如热轫致辐射场、黑体辐射场，以及非热低频幂律谱辐射场)，以便与实际观测谱形比较．计算表明：在满足匹配条件(即近似共振条件)下，RICS辐射效率很高，其谱形都是两段式(折断的)的幂律谱形式，与周边低频场性质无关．通过计算，再一次论证RICS机制是伽玛射线脉冲星和伽玛暴(GRBs)在高能射线段(硬X-射线和伽玛射线)辐射的一个理想的高效辐射机制。     

Hardening of Thermal Photons Through Inverse Compton Scattering in Strong Magnetic Fields

A new spectrum function is obtained by use of the Compton scattering cross section in the laboratory frame dervied earlier. This spectrum function, besides some modifications in the coefficients of the resonant term, contains also a non-resonant term which is inversely proportional to the square of the magnetic field. Based on this spectrum function, the hardening of thermal photons through inverse Compton scattering by relativistic electron beams on the surface of a strongly magnetized neutron star is investigated. Two new features are found. First, there is a maximum scattered photon energy for a given resonant scattering, beyond which resonance disappears. This maximum depends on the electron energy and the magnetic field, but is independent of the incident photon energy. Second, Beyond each resonant scattering, there is a high-energy tail, resulting from non-resonant scattering. It is also found that all the tails have a common upper limit which is the highest scattered photon energy for the given incident photon and electron energies. These two new features are absent in the Monte Carlo simulations and therefore, may have physical implications for γ-ray emissions.     

Maser Emission of Relativistic Electrons Spiralling and Drifting in Curved Magnetic Fields

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.     

强磁场中的逆Compton散射与γ射线爆能谱

本文认为强磁场中的逆Compton散射可能是γ射线爆的主要辐射机制.其能谱是由源区质子产生的低频光子经强磁场中非热电子的Compton散射形成的.我们利用非相对论情形(B/B_(cr)≤1,hv_i/m_ec~2≤1)下强磁场中的Compton散射微分截面,导出了上述Compton散射的辐射谱公式,由此很好地拟合了典型γ射线爆GB811016的观测能谱.     

On the aberration–retardation effects in pulsars

The magnetospheric locations of pulsar radio emission region are not well known. The actual form of the so-called radius-to-frequency mapping should be reflected in the aberration–retardation (A/R) effects that shift and/or delay the photons depending on the emission height in the magnetosphere. Recent studies suggest that in a handful of pulsars the A/R effect can be discerned with respect to the peak of the central core emission region. To verify these effects in an ensemble of pulsars, we launched a project analysing multifrequency total intensity pulsar profiles obtained from the new observations from the Giant Meterwave Radio Telescope (GMRT), Arecibo Observatory (AO) and archival European Pulsar Network (EPN) data. For all these profiles, we measure the shift of the outer cone components with respect to the core component, which is necessary for establishing the A/R effect. Within our sample of 23 pulsars, seven show the A/R effects, 12 of them (doubtful cases) show a tendency towards this effect, while the remaining four are obvious counterexamples. The counterexamples and doubtful cases may arise from uncertainties in the determination of the location of the meridional plane and/or the core emission component. Hence, it appears that the A/R effects are likely to operate in most pulsars from our sample. We conclude that in cases where those effects are present the core emission has to originate below the conal emission region.     

射电脉冲星的偏振特性与逆康普顿散射（ICS）模型

大量射电脉冲星的偏振观测－包括红偏振和圆偏振，个别脉冲的生直偏振模式，累积脉冲的消偏振现象等－为辐射区的物理状态和辐射提供了非常确切的观测事实，但现有理论对大从观测事实尚无法给出完整的说明，综述了脉冲星的偏振观测特征，并利用逆康谱顿散射模型对这些特性进行了解释。     

Spectroscopic evidence of charge exchange X‐ray emission from galaxies

What are the origins of the soft X‐ray line emission from non‐AGN galaxies? XMM‐Newton RGS spectra of nearby non‐AGN galaxies (including starforming ones: M82, NGC 253, M51, M83, M61, NGC 4631, M94, NGC 2903, and the Antennae galaxies, as well as the inner bulge of M31) have been analyzed. In particular, the Kα triplet of O VII shows that the resonance line is typically weaker than the forbidden and/or inter‐combination lines. This suggests that a substantial fraction of the emission may not arise directly from optically thin thermal plasma, as commonly assumed, and may instead originate at its interface with neutral gas via charge exchange. This latter origin naturally explains the observed spatial correlation of the emission with various tracers of cool gas in some of the galaxies. However, alternative scenarios, such as the resonance scattering by the plasma and the relic photo‐ionization by AGNs in the recent past, cannot be ruled out, at least in some cases, and are being examined. Such X‐ray spectroscopic studies are important to the understanding of the relationship of the emission to various high‐energy feedback processes in galaxies (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

活动星系核的非热致电子级联模型研究及其进展：纯康普顿机制冷却情形

活动星系核的高能辐射机制研究对于揭示其结构和演化特征以及中央驱动之迹具有其重要的意义。近十年来，随着活动星系统结构模型研究以及其高能连续谱观测的发展，解释活动星系统高能辐的非热致电子级联模型得以产生、发展和完善起来。     

Resonant cyclotron scattering in pulsar magnetospheres and its application to isolated neutron stars

Resonant cyclotron scattering(RCS)in pulsar magnetospheres is considered.The photon diffusion equation(Kompaneets equation)for RCS is derived.The photon system is modeled three dimensionally.Numerical calculations show that there exist not only up scattering but also down scattering of RCS,depending on the parameter space.RCS's possible applications to spectral energy distributions of magnetar candidates and radio quiet isolated neutron stars(INSs)are pointed out.The optical/UV excess of INSs may be caused by the down scattering of RCS.The calculations for RX J1856.5-3754 and RX J0720.4-3125 are presented and compared with their observational data.In our model,the INSs are proposed to be normal neutron stars,although the quark star hypothesis is still possible.The low pulsation amplitude of INSs is a natural consequence in the RCS model.     

Gamma-ray probe of cosmic ray pressure in galaxy clusters and cosmological implications

Cosmic rays produced in cluster accretion and merger shocks provide pressure to the intracluster medium (ICM) and affect the mass estimates of galaxy clusters. Although direct evidence for cosmic ray ions in the ICM is still lacking, they produce γ-ray emission through the decay of neutral pions produced in their collisions with ICM nucleons. We investigate the capability of the Gamma-ray Large Area Space Telescope ( GLAST ) and imaging atmospheric Čerenkov telescopes (IACTs) for constraining the cosmic ray pressure contribution to the ICM. We show that GLAST can be used to place stringent upper limits, a few per cent for individual nearby rich clusters, on the ratio of pressures of the cosmic rays and thermal gas. We further show that it is possible to place tight (≲10 per cent) constraints for distant  ( z ≲ 0.25)  clusters in the case of hard spectrum, by stacking signals from samples of known clusters. The GLAST limits could be made more precise with the constraint on the cosmic ray spectrum potentially provided by IACTs. Future γ-ray observations of clusters can constrain the evolution of cosmic ray energy density, which would have important implications for cosmological tests with upcoming X-ray and Sunyaev–Zel'dovich effect cluster surveys.     

Production of neutrons, neutrinos and gamma-rays by a very fast pulsar in the Galactic Centre region

We consider the possibility that the excess of cosmic rays near ∼10¹⁸ eV, reported by the AGASA and SUGAR groups from the direction of the Galactic Centre, is caused by a young, very fast pulsar in the high-density medium. The pulsar accelerates iron nuclei to energies ∼10²⁰ eV, as postulated by the Galactic models for the origin of the highest-energy cosmic rays. The iron nuclei, about 1 yr after pulsar formation, leave the supernova envelope without energy losses and diffuse through the dense central region of the Galaxy. Some of them collide with the background matter creating neutrons (from disintegration of Fe), neutrinos and gamma-rays (in inelastic collisions). We suggest that neutrons produced at a specific time after the pulsar formation are responsible for the observed excess of cosmic rays at ∼10¹⁸ eV. From normalization of the calculated neutron flux to the one observed in the cosmic ray excess, we predict the neutrino and gamma-ray fluxes. It has been found that the 1 km² neutrino detector of the IceCube type should detect from a few up to several events per year from the Galactic Centre, depending on the parameters of the considered model. Moreover, future systems of Cherenkov telescopes (CANGAROO III, HESS, VERITAS) should be able to observe  1–10 TeV  gamma-rays from the Galactic Centre if the pulsar was created inside a huge molecular cloud about  3–10×10³ yr  ago.