γ噪Blazar天体短时标光变的寄主星系影响

利用云南天文台1m光学望远镜2000～2001年对3个GeV和/或TeV γ噪Blazar天体的观测,发现γ噪类星体PKS 1510-089在R波段有一个光变时标为41min的星等变化为2.0mag的剧烈光变,这是迄今为止我们所观测到的变幅最大的一个γ噪Blazar天体短时标光变.对此光变,可估计限制光变辐射模型的一些参数,如辐射区半径R、多普勒因子δ以及吸积转化效率η等.η=59.6的值强烈预示着相对论聚束效应可较好解释γ噪Blazar天体的辐射机制.我们仔细考察了大气视宁度对光变的影响.发现对1ES 2344+514,观测到的光变与当地大气视宁度有一个弱相关,结果表明,对光变参数较小(C＜5)的光变,大气视宁度引起的假光变的贡献较大,需要选择较严格的光变判据.     

γ噪Blazar天体短时标光变的寄主星系影响

利用云南天文台1m光学望远镜2000－2001年对3个GeV和／或TeVγ噪Blazar天体的观测，发现γ噪类星体PKS 1510－089在R波段有一个光变时标为41min的星等变化为2．0mag的剧烈光变，这是迄今为止我们所观测到的变幅最大的一个γ噪Blazar天体短时标光变。对此光变，可估计限制光变辐射模型的一些参数，如辐射区半径R、多普勒因子δ以及吸积转化效率η等。η＝59．6的值强烈预示着相对论聚束效应可较好解释γ噪Blazar天体的辐射机制。我们仔细考察了大气视宁度对光变的影响。发现对1ES 2344＋514，观测到的光变与当地大气视宁度有一个弱相关，结果表明，对光变参数较小（C＜5）的光变，大气视宁度引起的假光变的贡献较大，需要选择较严格的光变判据。     

Blazar天体的辐射特性研究

收集了47个Blazar天体的短时标光变资料,估算了中心天体质量和不同波段辐射区域,并对估算结果作了统计分析,发现Blazar天体中心黑洞质量在10~7M_☉到10~(10)M_☉之间,BL Lac天体与平谱射电类星体中心黑洞质量有很大差异,平谱射电类星体中心黑洞质量大于BL Lac天体中心黑洞质量;红外波段和γ射线波段辐射区域大小相似.同时,利用收集到Blazar天体的热光度分析了Blazar天体热光度与短时标光变之间的关系,证实了射电选BL Lac(RBL)天体和平谱射电类星体(FSRQs)的辐射是强成束的,但相对论聚柬效应对X射线选BL Lac(XBL)天体的辐射影响较小.     

相对论电子的物理效应及其在高能天体中的应用

本文对相对论电子的辐射性质、能谱演化和加速机制等进行了简要的介绍。同时，对相对论电子在高能天体中的辐射作用和特性进行了简要的综述。本文给出了相对论电子在Blazar天体的射电辐射机制、光变机制、BL Lac天体的辐射机制以及γ暴的辐射机制等方面的应用研究成果。1、提出了相对论电子的光学薄同步辐射模型：解释Blazar天体的射电平谱：Blazar中心体的剧烈活动，使射电辐射区处于等离子体湍动状态，其中的相对论电子在湍动等离子体波的二交费米加速、激波加速、辐射损失、粒子逃逸和辐射区的绝热减速等物理过程作用下，形成较平的能谱，产生射电平谱。2、提出了新的Blazar天体光变模型：当Blazar天体爆发时，中心天体产生大量的相对论电子，注入喷流中；相对论电子产生同步辐射，并不断损失能量和逃逸辐射区，使它们的能谱快速变化，引起辐射发生快速光变。3、给出了BL Lac天体的等离子体反应堆模型：大量相对论电子从中心天体注入周围的等离子体反应堆中，通过同步辐射快速损失能量，同时这些电子同步吸收反应堆中不透明的光子，产生一个稳定、各向同性的幂律分布，其谱指数为γ＝3；然后，这些相对论电子通过等离子体反应堆的爆发或其表面扩散过程逃逸出来，辐射低频的同步辐射。模型解释了BL Lac天体的高频辐射表现出快速的谱变化性质，即流量减小时谱变陡。4、提出了相对论电子的内激波加速模型，解释γ暴的尖峰光变特性：在γ暴产生的相对论运动的壳层中，有内激波产生；激波在壳层中传播，耗散壳层的运动能，使其中的部分电子加速成为相对论电子。然后，这些电子通过同步辐射产生观测到的γ辐射。模型认为，γ暴中的每个尖峰辐射是一对内激波加速相对论电子的辐射过程，复杂的γ暴光变曲线是多对内激波辐射过程的叠加。     

AO 0235+164射电波段宽带谱指数周期性变化的研究

收集了AO 0235+164天体射电4.8 GHz和14.5 GHz波段的光变测量数据,并获得了长期的光变曲线,从光变曲线可以看出其活动是非常剧烈的。利用Jurkevich方法和自相关函数方法分别对AO 0235+164射电波段宽带谱指数进行周期性分析,并对流量和谱指数进行相关性分析,研究结果表明:(1)AO 0235+164天体射电波段4.8 GHz～14.5 GHz对应的宽带谱指数,可能存在5.30年的光变周期,与Liu等人用功率谱法在射电波段发现其流量密度可能存在5.59±0.47年的光变周期基本吻合;(2)宽带谱指数与流量密度之间存在相关性。     

基于自回归方法的Blazar天体3C 279和OJ 287光变周期研究

探索Blazar光变资料中的周期或准周期变化是1个有待深入研究的领域.由于光变资料的复杂性,目前寻找周期的算法还不够完善.文中以现代谱估计为基础,详细论述了自回归(Auto-regressive,AR)模型谱估计方法和最大熵谱估计的基本原理,分析了阶数选择对模型的重要影响,并把这些方法应用到类星体3C 279和BL Lac天体OJ287的光变周期分析中,得到它们的光变周期分别为7.14和11.76yr.通过验证,自回归 模型谱估计方法由于其分辨率高,可以作为1种较好的分析周期的方法.最后指出在应用谱估计分析Blazar天体的光变周期注意事项.     

AO0235＋164射电波段宽带谱指数周期性变化的研究

收集了AO0235＋164天体射电4．8GHz和14．5GHz波段的光变测量数据,并获得了长期的光变曲线,从光变曲线可以看出其活动是非常剧烈的。利用Jurkevieh方法和自相关函数方法分别对AO0235＋164射电波段宽带谱指数进行周期性分析,并对流量和谱指数进行相关性分析,研究结果表明：（1）AO0235＋164天体射电波段4．8GHz-14．5GHz对应的宽带谱指数,可能存在5．30年的光变周期,与Liu等人用功率谱法在射电波段发现其流量密度可能存在5．59±0．47年的光变周期基本吻合;（2）宽带谱指数与流量密度之间存在相关性。     

天文研究与技术-国家天文台台刊第4卷（2007）总目次

恒星物理再探伽玛射线暴中能量与脉冲宽度的依赖关系……………………………………邓家干,黄仁堂(1).1射电源的谱指数………………………………………………………………………袁聿海,李娟(1).11极贫金属星元素丰度及Ⅱ型超新星核合成产量…………………………马文娟,周贵德,张波(2).956颗Blazar天体的长期光变和色指数变化…………………………………………胡绍明,张雄(2).102活动星系核的演化与宇宙学红移……………………………………………………尤莉莎,张雄(2).108Blazar黑洞质量………………………………………谢照华,陈洛恩,郝建明,…     

类星体PKS 2251+158的长期光学光变周期分析

从有关文献中收集了Blazar天体PKS2251＋158近100年的光学观测数据,分析它的长期光变周期性．结果发现：PKS2251＋158在B波段观测到的最大变化幅度是△B＝2．86m．应用Jurkevich的方法分析B波段的数据,得到了一个12．39年的光变周期．在该天体中心可能有一个质量为M＝8．0ｘ105M的黑洞,并且γ辐射放大因子不小于7．2．另外,还对Jurkevich的方法进行了讨论．     

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...     

Variability of extragalactic objects in relation to redshift, color, radio spectral index and absorption lines

Optical variability of extragalactic objects, viz., QSOs, BL Lacs and Seyfert galaxies has been monitored systematically over an appreciable period of time and a large amount of data have accumulated. The present work reports results of investigations involving statistical analysis of updated data on relationships between variability and various observed properties of the objects, viz., redshift, color indices, radio spectral index and absorption lines. It is found that at high frequencies (rest frame) radio spectral index does not change significantly with the degree of variability. However, the degree of variability depends on redshifts. On the other hand, presence or absence of absorption lines is significantly associated with variability for QSOs with larger redshifts (z > 1.0), while no such relationship exists for QSOs at smaller redshifts (z < 1.0) or other objects. Correlation between color indices and redshifts depends on the degree of variability and the sample chosen for the color index.     

Long-term Variability Properties of Mkn501

Optical photometric observations at the I and R wavebands were carried out towards Mkn501 using the 1.56 meter optical telescope of Shanghai Astronomical Observatory at Sheshan. Combining our new observations with the published historical data, we have obtained the light curves of Mkn501 at the optical, infrared and radio wavebands with a time coverage of nearly 80 years. The relationship between the light variability and the color index is discussed, it is found that a strong correlation exists between the color indices (B − V) and (B − R), with the correlation coefficient reaching r = 0.73. The correlations of multi-band light variabilities are analyzed by the DCF method, it is found that certain positive correlations of B-band light variability with the 4.8 GHz and infrared light variabilities exist. And the spectral analysis on the B-band light curve with the CLEANest method indicates that the light curve of Mkn501 contains probably two periodical components of (10.06 ± 0.04) yr and (21.60 ± 0.17) yr.     

Variability Analysis of EGRET Gamma-Ray Sources

The variability of γ-ray sources listed in the third EGRET catalog is studied using three variability indices. These indices are found to be statistically equivalent if the observed data are sufficiently accurate. Using the three indices,30 EGRET point sources which are positionally coincident with pulsars and 40 persistent unidentified sources at low latitudes are analyzed for their variability status. It is found that 14 of the 30 point sources may have genuine or plausible associations with pulsars, and 16 of the 40 persistent unidentified sources are possible pulsar candidates.     

Chaotic Behaviour of Intra-Day Variability of BL Lac Object S5 0716+714

An optical monitoring shows Blazar object S5 0716+714 has complex Intra-Day Variability (IDV) behaviour. In this paper, we introduce a method of non-linear time series analysis, and calculate the correlation dimension of the IDV light curves of S5 0716+714 over seven nights in the December of 2006. According to our calculations, the correlation dimension D ≈ 1.993 ? 5.178 for all of the observed data, it is implied that the IDV behaviour may be a chaotic system with some additional noise.     

Search for variable sources using data of “Cold” surveys

We search for variable sources, using the data of the surveys conducted on the RATAN-600 radio telescope in 1980–1994 at 3.94 GHz. To test the radio sources of the RCR (RATAN Cold Refined) catalog for variability, we estimated the long-term variability indices V of the studied objects, their relative variability amplitudes V _χ , and the χ ² probabilities p. Out of about two hundred considered sources, 41 proved to have positive long-term variability indices, suggesting that these sources may be variable. Fifteen objects can be considered to be reliably variable according to the χ ² criterion p > 0.98, three of these sources have χ ² probabilities p ≥ 0.999. The corresponding probabilities for six sources lie in the 0.95 < p < 0.98 interval, and those of the remaining 20 objects in the 0.73 ≤ p < 0.95 interval. Twenty four of 41 objects are variable or possibly variable in the optical range, and five objects are known variable radio sources. We construct the light curves and spectra for the sources with positive long-term variability indices.     

Variability of Blazars

Variability is one of the characteristics of blazars. The rapid variability is superposed on the long term variation. In this work, the variability on different time scales, such as intra-day (IDV), short-term (STV) and long-term (LTV) variations are presented for some sources. We also presented our own observations of some selected objects, for which the historical data were compiled for periodicity analysis using several methods. The parameters of the binary black hole system OJ 287 are determined.     

Long-term optical color behavior of a sample of blazars

We report on the optical color variability of a sample of 24 blazars, consisting of nine flat spectrum radio quasars(FSRQs) and 15 BL Lacertae objects(BL Lacs), on timescales of years using simultaneous V-and R-band observations observed by the Kanata telescope at Higashi-Hiroshima Observatory.The correlations between color indices V-R and magnitudes reveal that 11 BL Lacs and one FSRQ exhibited significant(i.e., r 0.2 and P 0.01) bluer-when-brighter(BWB) trend and two FSRQs followed the redder-when-brighter(RWB) tend, indicating a possibility that the BWB chromatic trend is dominant for BL Lacs and the RWB trend is especially found in FSRQs, which has been presented occasionally in different samples of blazars.The superpositions of the red emission component from the Doppler-boosted relativistic jet and the blue component arising from the accretion disk might be a possible interpretation for the long-term color behaviors.     

Optical monitoring of quasars – I. Variability

We present an analysis of quasar variability from data collected during a photometric monitoring of 50 objects carried out at CNPq/Laboratório Nacional de Astrofísicá, Brazil, between 1993 March and 1996 July. A distinctive feature of this survey is its photometric accuracy, ∼0.02  V  mag, achieved through differential photometry with CCD detectors, which allows the detection of faint levels of variability. We find that the relative variability, δ σ L , observed in the V band is anticorrelated with both luminosity and redshift, although we have no means of discovering the dominant relation, given the strong coupling between luminosity and redshift for the objects in our sample. We introduce a model for the dependence of quasar variability on frequency that is consistent with multiwavelength observations of the nuclear variability of the Seyfert galaxy NGC 4151. We show that correcting the observed variability for this effect slightly increases the significance of the trends of variability with luminosity and redshift. Assuming that variability depends only on the luminosity, we show that the corrected variability is anticorrelated with luminosity and is in good agreement with predictions of a simple Poissonian model. The energy derived for the hypothetical pulses, ∼10⁵⁰ erg, agrees well with those obtained in other studies. We also find that the radio-loud objects in our sample tend to be more variable than the radio-quiet ones, for all luminosities and redshifts.     

Some Characteristics of the Circumstellar Shells of Stars with Variability of the R Coronae Borealis Type

The transformation of the line and molecular spectra of R CrB from absorption to emission at the 1985 minimum is traced from spectroscopic observations, and it is concluded for the first time, from a comparison with light curves and color indices, that the rapid variation of the color index U – B by –0^m.6 during fading is due exclusively to this transformation. The transformation of the spectrum can result in an increase in the star's brightness in the UBV photometric bands by about 1^m.4, 0^m.75, and up to 0^m.75, respectively. This removes one of the main objections to using the concept of a homogeneous spherical shell to interpret the R Coronae Borealis phenomenon. High-resolution spectroscopic observations of SV Sge, a star with variability of the R Coronae Borealis type, showed the presence of an intense circumstellar component in Na I D lines with a violet shift corresponding to 240 km/sec, which is unrelated to visible brightness minima. It is suggested that a stream of matter with such a velocity through the star's vicinity is the cause of the excitation not only of the broad emission features observed during brightness minima upon fading of the photospheric emission but also of the narrow ones. Assuming that a brightness minimum is associated with the temporary formation of another spherical screening shell, some characteristics of the permanent shell are determined. Its optical depth and geometrical thickness are 0.2-0.7 and at least 0.4 of its radius, respectively.