共查询到19条相似文献，搜索用时 171 毫秒
1.
在X射线天文学以及辐射物理学中,当硬X射线穿过" 冷"的等离子体时所发生的Compton软化是一种重要的辐射转移过程.简要介绍推广的Kompaneets方程,该方程在hv〈mec2及kTe〈mec2较宽松的条件下广泛成立,因此不仅能处理Compton硬化过程,而且也适用于Compton软化过程,后者在目前快速发展的X射线和γ射线天文学中十分重要.基于此方程,我们对天体物理中4种常见辐射谱(Gauss型发射谱线、黑体辐射谱、幂律辐射谱和热轫致辐射谱)在Compton软化情况下的谱演化进行了数值求解,并同Monte Carlo模拟结果做比较,证实了推广的Kompaneets方程的正确性和有效性.最后指出此方程在X射线天文学和γ射线天文学中的重要意义和潜在应用. 相似文献
2.
Blazar 的X射线谱性质 总被引：1，自引：0，他引：1
从Donato文献中选择了一个含有69个Blazar的样本，样本中每个源有多个X射线辐射流量数据，用该样本研究了流量密度和谱指数之间的关系，以及研究了三类源（HBL，LBL，FSRQ）的红移和谱指数的分布。结果表明：对于HBLs，谱指数和流量密度之间有一个较好的反相关关系存在，而对于LBLs和FSRQs却没有相关。因此认为HBL的X射线是同步辐射所致，而LBL和FSRQ的X射线辐射较为复杂可能是同步自康普顿过程导致。HBL显示软X射线谱，而FSRQ显示硬X射线谱，LBL居中。在谱图中HBL位于近端，rSRQ位于远端，LBL居中。 相似文献
3.
本文对脉冲式硬X射线暴的X辐射谱提出新的理论分析方法。指出电子数密度能态函数必须遵循基本动力学方程。在一些典型的源函数情形下,求得了电子数密度的能谱解。它们可以用来作为脉冲式硬X射线暴X辐射谱分析的基础。文中也对这些能态函数作了初步讨论,有助于说明X辐射谱的软化现象。 相似文献
4.
李泽清 《中国天文和天体物理学报》1982,(1)
在双星系统X射线源HerX-1的硬X射线波段测量到强的X射线谱线.第一条谱线在58keV,第二条谱线在110keV附近,并给出了谱线宽度,强度比和流量.对这种现象可以有几种解释,其中之一是认为这些谱线是由强磁场中量子化的电子同步加速辐射产生,从而可以推导出发射区的磁场强度.这几乎可以认为是宇宙中存在强磁场的 相似文献
5.
根据非局域热动平衡状态下谱线形成理论，利用相对论多组态原子程序软件包FAC模拟了类铍氧离子的X射线及EUV光谱．分析了间接过程对类铍氧离子X射线及EUV光谱形成的影响．在典型天体等离子体密度(ne=10加／立方厘米)情况下，采用了3种模型，在不同温度下模拟X射线及EUV光谱形成过程，分析比较了间接过程对谱线形成的贡献，并给出了它们的速率系数，得出了在谱线形成过程中，间接过程具有非常重要的作用． 相似文献
6.
本文综述了ASCA，RXTE，Beppo SAX和XMM－NEWTON对TeV耀变体（Blazar)X射线研究的最新进展。主要集中在X射线资料的时间和光谱分析的最重要的方面，包括功率谱密度，结构函数，带间时间延迟，同步峰值能量的漂移和谱演化。对这些新结果的物理意义也进行了简要讨论。 相似文献
7.
正在进行的实验室天体物理测量解决了X射线天文学的一些问题，这些实验产生了大量可靠的原子数据，它们既可用于电荷分布中电离与复合截面的计算，又可用于对X射线谱线形成的线表、激发截面及双电子复合系数的理解。另有一部分实验注重于解决天体观测的难题，以及验证现有的和寻找新的X射线谱线诊断。讨论了上述实验产生的数据类型，并展示了实验室测量如何为卫星（ASCA、EUVE、Chandra、XMM和ASTRO-E2）观测提供实验依据． 相似文献
8.
9.
对中小红移不同光度AGN的大蓝包位置进行了统计检验.主要统计方法是对比软X射线波段谱指数( SX)分布与 “直线”连接紫外1050和软X射线0.5 keV的幂指数(UV-SX)分布. 经过平均值统计和KS检验,表明二者分布是类似的. 因此,在1050至0.5 keV 中可能是幂律谱,统计预言大蓝包峰值在1050附近.这个统计结果在软X选低光度AGN样本(WF93)上亦能得到. 这表明WF93样品尽管普遍存在软X过剩,大蓝包峰值仍可能 在1050附近. 但是,软X射线谱指数 SX与1050到0.5 keV间“直线”连接的幂指数 UV-SX没有相关性,说明还存在一种不明的、但在远紫外(FUV)和极紫外(EUV)谱中 起作用的因素,它既能保证 UV-SX与 SX的分布在总体上的一致性,又使二者不具备一一对等的关系. 相似文献
10.
对中小红移不同光度AGN的大蓝包位置进行了统计检验．主要统计方法是对比软X射线波段谱指数（asx）分布与“直线”连接紫外1050■和软X射线0．5keV的幂指数（αuv-sx）分布．经过平均值统计和K－S检验,表明二者分布是类似的．因此,在1050■至O．5keV中可能是幂律谱,统计预言大蓝包峰值在1050■附近．这个统计结果在软X选低光度AGN样本（WF93）上亦能得到．这表明WF93样品尽管普遍存在软X过剩,大蓝包峰值仍可能在1050■附近．但是,软X射线谱指数。αsx与1050■到0.5keV间“直线”连接的幂指数αuv-sx没有相关性,说明还存在一种不明的、但在远紫外（FUV）和极紫外（EUV）谱中起作用的因素,它既能保证。。αuv-sx与αsx的分布在总体上的一致性,又使二者不具备—一对等的关系． 相似文献
11.
Zongjun Ning 《Solar physics》2008,247(1):53-62
This paper explores the time evolution of microwave and hard X-ray spectral indexes in the solar flare observed by Nobeyama
Radio Polarimeters (NoRP) and the Ramaty High Energy Solar Spectroscopy Imager (RHESSI) on 13 December 2006. The microwave
spectral index, γ
MW, is derived from the emissions at two frequencies, 17 and 35 GHz, and hard X-ray spectral index, γ
HXR, is derived from RHESSI spectra. Fifteen subpeaks are detected at the microwave and hard X-ray emissions. The microwave spectral
indexes tend to be harder than hard X-ray spectral indexes during the flare, which is consistent with previous findings. All
detected subpeaks follow the soft-hard-soft spectral behaviours in the hard X-ray rise-peak-decay phases. However, the corresponding
microwave subpeaks display different spectral behaviour, such as soft-hard-soft, soft-hard-harder, soft-hard-soft + hard or
irregular patterns. These contradictions reveal the complicated acceleration mechanism for low- and high-energy electrons
during this event. It is also interesting that the microwave interpeak spectral indexes are much more consistent with one
another. 相似文献
12.
The X-ray and γ-ray flux densities of 18 γ-loud BL Lac objects as well as their average spectral indices of X-ray wave band (1 keV) and γ-ray wave band (>100 MeV) are collected, and the correlations among the various quantities are examined. The results indicate: (1) The X-ray flux density and the γ-ray flux density exhibit rather strong correlations in all the states, high, low or mediate. (2) Between the mean spectral indices in X-ray and γ-ray wave bands there is a comparatively intense anti-correlation. (3) Between the average spectral indices and the X-ray and γ- flux densities there is no evident correlation either in the high or the mediate state. (4) Between the average spectral index of γ-ray wave band and the flux density of X-rays in low state there is a rather strong anticorrelation. Between the mean spectral index of X-ray wave band and the γ-flux density in low state there also exists a weak correlation. The results of our analysis support the viewpoint that both the X-ray and γ-ray emissions of BL Lac objects come from the synchrotron radiation and synchrotron self Compton (SSC) radiation with one and the same distribution of relativistic electrons. 相似文献
13.
S. W. Allen 《Monthly notices of the Royal Astronomical Society》2000,315(2):269-295
We discuss the X-ray properties of the cooling flows in a sample of 30 highly X-ray luminous clusters of galaxies, observed using the ASCA and ROSAT satellites. We demonstrate the need for multiphase models to consistently explain the spectral and imaging X-ray data for the clusters. The mass deposition rates of the cooling flows, independently determined from the ASCA spectra and ROSAT images, exhibit good agreement and exceed 1000 M⊙ yr−1 in the largest systems. We confirm the presence of intrinsic X-ray absorption in the clusters using a variety of spectral models. The measured equivalent hydrogen column densities of absorbing material are sensitive to the spectral models used in the analysis, varying from average values of a few 1020 atom cm−2 for a simple isothermal emission model, to a few 1021 atom cm−2 using our preferred cooling flow models, assuming in each case that the absorber lies in a uniform foreground screen. The true intrinsic column densities are likely to be even higher if the absorbing medium is distributed throughout the clusters. We summarize the constraints on the nature of the X-ray absorber from observations in other wavebands. Much of the X-ray absorption may be caused by dust. 相似文献
14.
Anna Szostek rzej A. Zdziarski Michael L. McCollough 《Monthly notices of the Royal Astronomical Society》2008,388(3):1001-1010
We present a detailed classification of the X-ray states of Cyg X-3 based on the spectral shape and a new classification of the radio states based on the long-term correlated behaviour of the radio and soft X-ray light curves. We find a sequence of correlations, starting with a positive correlation between the radio and soft X-ray fluxes in the hard spectral state, changing to a negative one at the transition to soft spectral states. The temporal evolution can be in either direction on that sequence, unless the source goes into a very weak radio state, from which it can return only following a major radio flare. The flare decline is via relatively bright radio states, which results in a hysteresis loop on the flux–flux diagram. We also study the hard X-ray light curve, and find its overall anticorrelation with the soft X-rays. During major radio flares, the radio flux responds exponentially to the level of a hard X-ray high-energy tail. We also specify the detailed correspondence between the radio states and the X-ray spectral states. We compare our results to those of black hole and neutron star binaries. Except for the effect of strong absorption and the energy of the high-energy break in the hard state, the X-ray spectral states of Cyg X-3 closely correspond to the canonical X-ray states of black hole binaries. Also, the radio/X-ray correlation closely corresponds to that found in black hole binaries, but it significantly differs from that in neutron star binaries. Overall, our results strongly support the presence of a black hole in Cyg X-3. 相似文献
15.
R. K. Manchanda 《Journal of Astrophysics and Astronomy》2002,23(3-4):197-212
The attempts at unified model fitting to explain the spectral variations in Cyg X-3 suggest equally probable fits with a combination
of an absorbed blackbody and a separately absorbed power law with an exponential cut-off or a composite of absorbed free-free
emission with a power law hard X-ray component apart from the iron emission line. These seemingly ordinary but ad hoc mixtures
of simple X-ray emission mechanisms have a profound implication about the geometry of the X-ray source. While the first set
suggests a black-hole nature of the compact object, the second combination is consistent with a neutron star binary picture.
The spectral variability at hard X-ray energies above 30 keV can provide crucial input for the unified picture. In this paper,
we present spectral observations of Cyg X-3, made in our on-going survey of galactic and extragalactic X-ray sources in the
20–200 keV energy region, using Large Area Scintillation counter Experiment. The data show a clear power-law photon spectrum
of the form dN/dE ∼ E−2.8 in the 20 to 130 keV energy range. A comparison with earlier data suggests that the total number of X-ray photons in the
entire 2–500 keV energy band is conserved at all time for a given luminosity level irrespective of the state. We propose that
this behaviour can be explained by a simple geometry in which a thermal X-ray source is embedded in a hot plasma formed by
winds from the accretion disk within a cold shell. The high/soft and low/hard X-ray states of the source are simply the manifestation
of the extent of the surrounding scattering medium in which the seed photons are Comptonized and hot plasma can be maintained
by either the X-ray driven winds or the magneto-centrifugal winds. 相似文献
16.
《天文和天体物理学研究(英文版)》2021,(8)
X-ray changing-look active galactic nuclei(CL AGNs) are a subpopulation of AGNs, whose lineof-sight column densities increase/decrease within several years. The physical mechanism for the variation of column density is unclear. We reduce the X-ray data from XMM-Newton and Nu STAR observations for a CL AGN NGC 1365 with strong variation of column densities. The X-ray spectrum quickly softens as the X-ray luminosity increases and optical-to-X-ray spectral index also increases as increasing of optical luminosity. These results support that NGC 1365 also undergoes strong spectral evolution as that recently suggested for the optically selected CL AGNs with reappearance/disappearance of broad emission lines.Therefore, the variation of column density may be driven by the variable disk winds during the strong evolution of disk/corona. 相似文献
17.
Richard G. Teske 《Solar physics》1969,6(2):193-204
Solar X-rays from 8–12 Å have been observed with an ion chamber photometer and fluxes derived from the observations after an assumption concerning the spectral distribution. The time variation of the X-ray flux correlates well with the radio flux, plage index, and sunspot number. Comparisons of X-ray and optical events are given; flares seem to produce soft X-rays, but some soft X-ray bursts are apparently not associated with flares. The total energy involved in the soft X-ray bursts may be a significant amount of the total flare radiation. 相似文献
18.
Julien Malzac 《Monthly notices of the Royal Astronomical Society》2001,325(4):1625-1636
We study a phenomenological model for the continuum emission of Seyfert galaxies. In this quasi-spherical accretion scenario, the central X-ray source is constituted of a hot spherical plasma region surrounded by spherically distributed cold dense clouds. The cold material is radiatively coupled with the hot thermal plasma. Assuming energy balance, we compute the hard X-ray spectral slope Γ and the reflection amplitude R . This simple model enables us to reproduce both the range of observed hard X-ray spectral slopes and the reflection amplitude R . It also predicts a correlation between R and Γ that is very close to what is observed. Most of the observed spectral variations from source to source would be caused by differences in the cloud covering fraction. If some internal dissipation process is active in the cold clouds, darkening effects may provide a simple explanation for the observed distributions of reflection amplitudes, spectral slopes and ultraviolet to X-ray flux ratios. 相似文献
19.
According to the theory of spectral line formation in the state of non-local thermodynamic equilibrium and by using the software package FAC for the relativistic multi-configuration atomic processes, the X-ray and EUV spectra of Be-like oxygen ions are simulated. The effects of indirect processes on the X-ray and EUV spectra of Be-like O ions are probed. In the situation of the typical cosmical plasma density (ne = 1010/cm3), three models are adopted. For different temperatures, the processes of formation of X-ray and EUV spectra are simulated, and the contributions of indirect processes to the formation of spectral lines are analyzed and compared. Besides, their rate coefficients are given. It is found that in the process of spectral line formation, the indirect processes have exceedingly important effects. 相似文献