The infrared variability of QSO 3C 273

The near-infrared data of the quasar 3C273 are collected from available literature and are used to analyze its variability properties. The largest amplitudes of variations are ΔJ = 1.0, ΔH = 0.9, and ΔK = 0.86. The color indices are J − H = 0.82, J − K = 1.96, and H − K = 1.13. Analysis with the discrete correlation function (DCF) method indicates that the variability between any two infrared bands is correlated without any time lag. The relation between the color index and brightness is also investigated and the result indicates that the spectrum steepens when the source first dims, while it flattens after the source has dimmed to a some extent, suggesting that the emission of 3C 273 at near-IR consists of at least two components. Some discussions are presented.     

Comparison and Analysis of the Light Variations of 3C 273, 3C 279 and 3C 345

The blazar 3C 345 is quite similar to the γ-ray blazar 3C 279 in respect of redshift, spectral energy distribution from the radio to the X-ray wave band, and so on. However, it was not detected by EGRET. We compared the differences and similarities between 3C 345 and the γ-ray sources 3C 279 and 3C 273 in respect of variation amplitudes (in the 8 GHz, 22 GHz, 37 GHz and B band), the smallest variation time scales in the optical and the time lags between different bands to search possible reason for the lack of the γ-ray radiation in 3C 345. From our analyses it is found that the variation amplitudes in the radio band for 3C 345 and 3C 279 are quite similar; the variation amplitudes in the optical wave band gradually decrease in the order 3C 279, 3C 345 and 3C 273, and variations on the order of days are found in these three sources. It is also found that the time lag in 3C 345 is much longer than that in 3C 279 and is approximately the same as that in 3C 273. Based on the similarity of other observational properties between 3C 345 and 3C 273, such as the presence of the big blue bump and their comparable infrared luminosities, it is proposed that the spectral energy distribution and the luminosity in the γ-ray band for 3C 345 are similar to those for 3C 273. It is indicated by our simple calculations that if 3C 273 has a similar redshift to that of 3C 345, then even at the burst state, EGRET could not detect any radiations from 3C 273. This might be the reason why 3C 345 had never been detected by EGRET.     

XMM–Newton observations of the hot-gas atmospheres of 3C 66B and 3C 449

We present new XMM–Newton observations of the hot-gas environments of two low-power twin-jet radio galaxies, 3C 66B and 3C 449, showing direct evidence for the interactions between X-ray-emitting gas and radio plasma that are thought to determine the large-scale radio structure of these sources. The temperatures that we measure for the two environments are significantly higher than those predicted by standard luminosity–temperature relations for clusters and groups. We show that luminosity–temperature relations for radio-quiet and radio-loud X-ray groups differ, in the sense that radio-source heating may operate in most groups containing radio galaxies. If the radio lobes are expanding subsonically, we find minimum ages of  3 × 10⁸ yr  for 3C 66B, and  5 × 10⁸ yr  for 3C 449, older than the values obtained from spectral ageing, which would give the radio source sufficient time to heat the groups to the observed temperatures for plausible values of the jet power. The external pressures in the atmospheres of both radio galaxies are an order of magnitude higher than equipartition estimates of their radio-lobe pressures, confirming that the radio lobes either are out of equipartition or require a pressure contribution from non-radiating particles. Constraints from the level of X-ray emission we measure from the radio lobes allow us to conclude that a departure from equipartition must be in the direction of magnetic domination, and that the most plausible candidates for a particle contribution to lobe pressure are relativistic protons, an additional population of low-energy electrons, or entrained and heated thermal material.     

Chaotic Feature in the Light Curve of 3C 273

Some nonlinear dynamical techniques, including state-space reconstruction and correlation integral, are used to analyze the light curve of 3C 273. The result is compared with a chaotic model. The similarities between them suggest there is a low-dimension chaotic attractor in the light curve of 3C 273.     

A Possible Periodicity in the Radio Light Curves of 3C 454.3

During the period 1966.5–2006.2 the 15GHz and 8GHz light curves of 3C 454.3 (z = 0.859) show a quasi-periodicity of ～12.8 yr (～6.9 yr in the rest frame of the source) with a double-bump structure. This periodic behaviour is interpreted in terms of a rotating double-jet model in which the two jets are created from the black holes of a binary system and rotating with the period of the orbital motion. The periodic variations in the radio fluxes of 3C 454.3 are suggested to be mainly due to the lighthouse effects (or the variation in Doppler boosting) of the precessing jets caused by the orbital motion. In addition, variations in the rate of mass accreting onto the black holes may be also involved.     

Infrared variability properties of the blazar 3C 279

The long-term (about 27 years) near-infrared K light curve is constructed from the published literature for the blazar 3C 279. The Jurkevich method is adopted to analyse the periodicity, and a strong 7.1±0.44 yr period is found, suggesting that the next near-infrared outburst will occur in 2002/03. The correlation between colour index (spectral index) and magnitude is discussed, and a significant correlation between ( J − H ) and K is found with a correlation coefficient r =0.72 ( p =2.0×10⁻¹⁰), which is consistent with Brown et al.'s proposal.     

X-ray analysis of the cluster 3C 129

The cluster 3C 129 is classified as a rich cluster. An analysis of the properties of the cluster 3C 129 from ROSAT PSPC and HRI, Einstein IPC, and EXOSAT ME observations is presented. The mean temperature from a joint fit of the ROSAT PSPC and EXOSAT ME data is 5.5(±0.2) keV. The luminosity is 0.6×10⁴⁴ erg s⁻¹ in 0.2–2.4 keV and 2.7×10⁴⁴ erg s⁻¹ in 0.2–10 keV. We find a cooling flow with a rate of ∼84 M_⊙ yr⁻¹. The central gas density is 6×10⁻³ cm⁻³, and the ICM mass is 3.6×10¹³ M_⊙. The total cluster mass is ∼5×10¹⁴ M_⊙. The X-ray morphology shows an east–west elongation, which is evidence for a recent merger event. The radio source 3C 129.1 is located near the X-ray centre. Another cluster member galaxy (the radio galaxy 3C 129) is a prototype of head-tailed radio galaxies, and is located in the west part of the cluster. The tail points along the gradient of intracluster gas pressure. There are no significant point X-ray sources associated with the AGNs of the two radio galaxies.     

Chandra measurements of the X-ray core and cluster of 3C 220.1

We report results of an 18-ks exposure with the ACIS instrument on Chandra of the powerful z =0.62 radio galaxy 3C 220.1. The X-ray emission separates into cluster gas of emission-weighted kT ∼5 keV , 0.7–12 keV luminosity (to a radius of 45 arcsec) of 5.6×10⁴⁴ erg s⁻¹ and unresolved emission (coincident with the radio core). While the extended X-ray emission is clearly thermal in nature, a straightforward cooling-flow model, even in conjunction with a point-source component, is a poor fit to the radial profile of the X-ray emission. This is despite the fact that the measured properties of the gas suggest a massive cooling flow of ∼130 M_⊙ yr⁻¹, and the data show weak evidence for a temperature gradient. The central unresolved X-ray emission has a power-law spectral energy index α ∼0.7 and 0.7–12 keV luminosity of 10⁴⁵ erg s⁻¹, and any intrinsic absorption is relatively small. The two-point spectrum of the core emission between radio and X-ray energies has α _rx=0.75 . Since this is a flatter spectrum than seen in other sources where the X-ray emission is presumed to be radio-related, regions close to the active galactic nucleus (AGN) in this source may dominate the central X-ray output, as is believed to be the case for lobe-dominated quasars. Simple unification models would be challenged if this were found to be the case for a large fraction of high-power radio galaxies.     

类星体3C 446射电光变非线性特性分析

类星体有剧烈、大幅度的光变现象, 光变研究有助于建立与观测相符的理论模型. 这篇文章从密歇根大学射电天文台数据库收集了类星体3C 446射电4.8、8.0和14.5GHz波段的长期观测数据. 传统的线性方法难以分析复杂的光变现象, 文章采用了集合经验模态分解(Ensemble Empirical Mode Decomposition, EEMD)方法和非线性分析方法相结合, 从混沌动力学特性、分形特性和周期性多角度对类星体光变随时间演化的规律进行了较全面的分析, 并重点对比分析了除去周期成分或混沌成分前后, 光变的周期性和非线性特性是否存在明显区别. 分析结果表明, 类星体3C 446射电波段光变资料由周期成分、趋势成分和混沌成分组成, 光变具有周期性、混沌性和分形特性. 除去混沌成分和趋势成分后的光变周期与原始光变资料的周期完全相同, 而两者的混沌和分形特性有明显不同. 从饱和关联维数来看, 重构动力学系统时, 除去周期成分和趋势成分后的光变资料比原始光变资料需要更多的独立参量, Kolmogorov熵值表明前者信息的损失率比后者大, 系统的混沌程度更高, 系统也更复杂, Hurst值表明后者自相似性和长程相关性比前者略强.     

Soft X-ray variability of the bright quasar 3C273

We present the results from ROSAT observations of 3C273 in the soft X-ray band. The light variation of 3C273 was investigated for three different energy bands of soft, medium, and hard. The maximum variability with a factor of 2 for 551 days was confirmed at all three different bands. This appears to be a periodic variation within the period of roughly 6 months. However, the short-term or micro variation was not so distinct and the light variation of each band did not show any correlation between them. The hardness ratio for hard and soft bands shows irregular variation but there was no correlation between them. There is no distinct variation of the photon index in the case of simple power law model fitting. For power law + free absorption model fitting, the average photon index (Γ) is 2.08.     

The infrared jet in 3C 66B

We present images of infrared (IR) emission from the radio jet in 3C 66B. Data at three wavelengths (4.5, 6.75 and 14.5 μm) were obtained using the Infrared Space Observatory . The 6.75-μm image clearly shows an extension aligned with the radio structure. The jet was also detected in the 14.5-μm image, but not at 4.5 μm. The radio–infrared–optical spectrum of the jet can be interpreted as synchrotron emission from a population of electrons with a high-energy break of 4×10¹¹ eV. We place upper limits on the IR flux from the radio counter-jet. A symmetrical, relativistically beamed twin-jet structure is consistent with our results if the jets consist of multiple components.     

Extended X-ray emission in the radio-loud galaxy 3C 382

ROSAT /HRI observations of the powerful radio-loud galaxy 3C 382 reveal extended X-ray emission associated with the source. On the basis of this new spatial component, a previous ROSAT /PSPC spectral analysis of the source is revised. Allowing for the presence of an additional thermal component in the PSPC spectrum, the non-thermal component is found to be compatible with the extrapolation of the well-defined 3C 382, 2–10 keV, power-law spectrum into the soft X-ray region. The thermal – extended – component would then account for the soft excess emission previously reported for this source. The origin of this thermal component is not clear. Its luminosity compares with that of rich Abell clusters; yet, the galaxy environment in 3C 382 appears of moderate optical richness. An alternative is that it is the result of a massive extended gaseous atmosphere sustained by the deep gravitational potential well of 3C 382.     

Simultaneous X-ray and IR variability in the quasar 3C 273

From a combination of high-quality X-ray observations from the NASA Rossi X-ray Timing Explorer ( RXTE ) and IR observations from the UK Infrared Telescope (UKIRT) we show that the medium-energy X-ray (3–20 keV) and near-IR fluxes in the quasar 3C 273 are highly correlated. It is widely believed that the X-ray emission in quasars like 3C 273 arises from Compton scattering of low-energy seed photons, and our observations provide the first reliable detection of correlated variations in 3C 273 between the X-ray band and any lower energy band. For a realistic electron distribution we demonstrate that it is probable that each decade of the seed-photon distribution from the mm to IR wavebands contributes roughly equally to the medium-energy X-ray flux. However, the expected mm variations are too small to be detected above the noise, probably explaining the lack of success of previous searches for a correlation between X-ray and mm variations. In addition, we show that the IR leads the X-rays by  0.75±0.25 d  . These observations rule out the 'External Compton' emission process for the production of the X-rays.