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.     

Constraints on a soft X-ray excess in the quasar 3C 279

We present the results of a three-week daily monitoring campaign of the quasar 3C 279 by the X-ray satellites RXTE ROSAT . A cross-correlation provides no evidence for any time lag between the very similar soft and hard X-ray light curves, and the source shows no significant spectral variability over the observing period. There is no evidence to support the presence of a soft excess, with a 99 per cent upper limit on any such component of 25 per cent of the total observed luminosity in the 0.1–2 keV band (<3 × 10³⁸ W). This fraction (but not the luminosity) is significantly lower than that of the soft excess observed in 3C 273.     

Spectral variability in hard X-rays and the evidence for a 13.5 years period in the bright quasar 3C273

We report the observation of nearest quasar 3C273 made with LASE instrument on November 20th, 1998 as a part of our continuing programme of balloon borne hard X-ray observations in the 20–200 keV band using high sensitivity Large Area Scintillation counter Experiment. Our data clearly show a steep spectrum in the 20–200 keV with power law spectral indexα = 2.26 ± 0.07. This is in complete contrast to the reported data from OSSE and BeppoSAX which suggest the value of 1.3 to 1.6 for the power law index in the X-ray energy band, but is quite consistent with the value derived for the high energy gamma ray data. A single power law fit in the X-ray and gamma ray energy bands points to a common origin of these photons and the absence of spectral break around 1 MeV as suggested in literature. We have reanalyzed the available data to study the temporal variability of the spectrum in the hard X-ray band. Our analysis reveals that 50 keV flux from the source, shows a strong modulation with a period of about 13.5 years. The analysis of the optical light curve of the source also supports the 5000 day period. We discuss the emission mechanism and the possible sites for X-ray photons along with the implications of the long term periodicity with respect to source geometry.     

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.     

基于EMD-AR谱的3C 273光变周期分析

光变是Blazar最显著的观测特征之一,有的光变呈准周期性. Blazar周期光变可能为其中心黑洞和吸积盘等内部物理结构提供重要信息.因此,周期分析对于讨论Blazar的光变有重要意义.结合经验模态分解(Empirical Mode Decomposition, EMD)和自回归(Auto-regressive, AR)模型谱估计方法的优点,提出了一种基于EMD-AR谱的组合光变周期分析新方法.先对观测数据进行EMD分解,得到各阶模态分量,并计算其与原始光变曲线的相关系数,再取相关度高的分量求和后估算AR谱,最后将此功率谱的周期分析方法用于天体的光变数据分析.讨论了EMD-AR谱方法的原理和应用步骤,并用此方法对类星体3C 273在1887—2016年的观测数据进行了分析,得到3C 273的长时标周期分别为:21.23、13.51、11.02、5.51、4.69、3.79、2.76 yr,与文献中常用方法的分析结果有很好的一致性;短时标周期分别为:(30±1)、(15±0.3)、(7.5±0.2)、(10±0.1)、(5±0.6)、(6±0.4)和(3±0.5) min,此结果未见相关...     

Spectral Reversal and Stratification of the Jet in 3C 273

Quasi-simultaneous VLBI observations at 15-86 GHz have shown that in the classical superluminal radio source 3C 273, the spectral index α(Sv∝v^α) has a systematic variation along the jet. For epoch 1995.15, a spectral reversal was observed at core distance -1.5mas, where the superluminal knot C12 Located. Similarly, for epoch 1997.18, two spectral reversals wrer observed at core distances of -1.8 mas and -4.2 mas ,where superluminal knots C11 and C14 were, respectively. These spectral reversals are associated with local maxima of the jet width. We suggest that this phenomenon may be related to a stratification of the jet structure, i.e., its physical parameters (flow velocity, Doppler factor, electron density and energy, magnetic field strength,etc.) are substantially dependent on the distance from the jet axis. These properties may be naturally formed through gasdynamic processes when the jet expands into a lower pressure ambient medium.     

The long-term multiband optical observations and colour index for the quasar 3C 273

The long baseline simultaneous multiband ( BVRI ) observations of blazar 3C 273 are presented. We have made 758 optical multiband observations with the Yunnan Astronomical Observatory (YAO) 103 cm and Shanghai Astronomical Observatory (SHAO) 156 cm from 2003 January to 2005 April. In our observational campaign, the average colour indices are   B − V = 0.21, V − R = 0.26  and   R − I = 0.31  . The mean magnitudes in B, V, R and I are 12.895, 12.698, 12.441 and 12.139, respectively. The source is in a steady state over observational campaign. The correlations between colour index and brightness are discussed. We find that the correlations of   B − V   versus B ,   V − R   versus V and   R − I   versus R have significant negative correlation, while   B − V   versus V ,   V − R   versus R and   R − I   versus I have positive correlation. These strong correlations imply that the spectrum becomes bluer (flatter) when the source becomes brighter, and redden (softer) when the source fades both in intraday and long-term variability. The spectral evolution trends of 3C 273 are consistent with those of BL Lac objects.     

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.     

Simultaneous EUV and X-ray variability of NGC 4051

We present a flux variability study of simultaneous RXTE and EUVE observations of the highly variable Seyfert galaxy NGC 4051. We find a strong correlation between variability in the EUV and medium-energy X-ray bands, indicating that both are sampling the same power-law continuum. The lag between the two bands is less than 20 ks and, depending on model assumptions, may be <1 ks. We examine the consequences of such a small lag in the context of simple Comptonization models for the production of the power-law continuum. A lag of <1 ks implies that the size of the Comptonizing region is less than 20 Schwarzschild radii for a black hole of mass >10⁶ M_⊙.     

Periodic Variations of the Jet Flow Lorentz Factor in 3C 273

1 INTRODUCTIONThe quasar 3C 273 (z = 0.158) is one of the classical rwho sources showal apparellt superltalnal motion (Zensus et al. 1990, 1997). It has a large-scale jet (~ 20n of length, 3C273A)elliltting at radio, optical and X-ray bands. It has been suggested that its compel source(3C 273B) is a rmm-blazar, Undergoing strong and rapid Variations in ratio, optical-UV, X-rayand 7-my bands at various tab scales (from hours to years, Courvoisier et al. 1998, Tet al. 1999, Stevens et …