3C 345和3C 273的光变分析

用结构函数法,对两个经典的blazar 3C 273和3C 345的22 GHz、37 GHz和光学波段的数据进行了周期分析.结果显示,3C 273的周期性比较明显,22 GHz经分析存在7.0年和14.7年的周期,37 GHz存在7.2年和14.5年的周期,同时它的光学波段可能存在0.7年和8.7年的周期.3C 345的37 GHz存在比较明显的8.8年的周期,22 GHz和光学波段分别存在不太明显的9.3年和10.2年的周期.     

致密对称源OQ208自行的研究

利用美国甚长基线阵,在5GHz和8GHz波段观测致密对称源(CSO)OQ208,由获得的总流量图均显示OQ208是由2个主要的射电结构组成。5GHz波段在该源西南(SW)部分和东北(NE)部分都探测到2个子源。8GHz波段在该源(SW)部分探测到2个子源,而在(NE)部分探测到3个子源。在5GHz波段,根据子源A和D自1993年到2001年间的5个时段VLBI观测成图结果,拟合出它们的分离速度为0.037±0.006mas/a(年)。在8GHz波段,根据1994年到2002年间的9个时段观测数据,获得子源A和C的分离速度为0.046±0.009mas/a。     

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。     

三波段太阳射电高时间分辨率的同步观测

本文主要介绍使用三波段(1.42GHz、2.84GHz及3.67GHz)高时间分辨率同步观测系统巡视太阳,在日面上有活动区时所观测到的一些快速精细结构特征,特别注意到在毫秒级尖峰辐射中可能存在谐波结构的现象。     

致密陡谱源1150+497(4C49.22)的射电研究

利用美国甚长基线阵,在5GHz和8GHz波段观测致密陡谱源(CSS)1150+497,获得的5GHz总流量图显示1150+497有单边喷流结构。在5GHz波段该源的西南方向探测到3个亮结,在东北方向探测到一个亮结。在8GHz波段该源的西南方向探测到2个亮结。在5GHz波段,根据子源A和E自1982~2001年间3个时段的VLBI观测成图结果,拟合出它们的分离速度为0.478±0.007mas/year。     

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。     

低峰频blazars的射电光变分析

从大量文献资料中收集了6个低峰频blazars(BL Lacertae、0235+164、OQ530、0716+714、3C 345及3C 273)最近30多年来在4.8 GHz、8 GHz、14.5 GHz、22GHz和37 GHz最完备的光变数据.利用离散相关函数法对这6个源的相关性及延迟进行分析,利用结构函数法对6个源的光变曲线的光变周期和光变时标进行分析并对其光变幅度进行比较分析.分析结果显示:在光变幅度方面,0716+714和0235+164在6个blazars中的光变幅度相对较大,3C 345和OQ 530次之,3C 273和BL Lacertae的光变幅度相对较小;多波段的延迟分析显示0235+164在相邻两波段之间都显示高频波段要超前于低频波段的变化趋势,3C 345整体呈现出高频波段滞后于低频波段的变化趋势.其余blazars分析结果显示在部分射电波段之间呈现出高频波段要超前于低频波段的变化趋势,而在其余射电波段之间却呈现出高频波段滞后于低频波段的变化趋势;结构函数法的分析结果显示3C 345的光变时标、拟合斜率及光变周期与其它5个低峰频blazars相比都偏大,这表明3C 345的活动性与其它5个源相比较弱,这表明在3C 345内部可能存在与其它5个低峰频blazars不同的物理过程.     

射电源AO 0235＋164不同波段之间的相关时延分析及谱指数演化

详细介绍了由Edelson和Krolik提出的离散相关分析方法，该方法比较适合于因天文观测的不规则性而引起的时间分布不均匀的不同波段之间流量的相关分析，取两种极端的情况（完全相关和完全不相关）对该方法进行了测试，结果表明这是一种比较切实可行的方法。利用它，对AO0235＋164在4个波段上流量变化作相关性分析，结果表明，AO 0235＋164在5GHz,8GHz,14.5GHz和光学BI皮段的辐射之间存在着明显的相关性，高频波段的流量变化早于低频波段的流量变化，表明这些波段的辐射（从射电到光学）可能来源于相同的辐射机制，或者辐射是相关的，另外发现，谱指数随着时间而发生变化，这种变化在5GHz 8GHz和14．5GHz之间多表现为逆谱的形式，种种迹象表明AO 0235 164的射电爆发可能是和激波的形成有关，多波段的频谱分析和频谱演化研究可能是揭示这种关系的有效途径。     

X射线选射电噪活动星系核的多波段性质(英文)

基于被ROSAT全天区巡天观测和射电 4.85GHz巡天观测同时探测到的活动星系核的大样本 ,研究了X射线选的射电噪活动星系核的多波段性质 .通过分析该样本中的活动星系核的宽波段能量分布 ,确认了来自射电、光学和X射线波段的辐射光度之间的显著相关性 .这种相关性对于类星体、赛弗特、蝎虎座天体和射电星系是有区别的 .同时 ,探讨了从光学到X射线波段之间的谱指数与红移以及 50 0 0 和 4.85GHz处的单色光度的相关性     

处理相关光变时间延迟的新方法

时间延迟相关函数(Time Delay Correlation Function,TDCF)方法是一种可以计算时间序列时间延迟的新方法,利用该方法计算blazar天体0316+413(NGC 1275)3个射电波段(4.8 GHz、8 GHz和14.5 GHz)的时间延迟并进行另外7个blazar源的多波段相关分析.对0316+413的计算结果表明:4.8 GHz光变延迟8 GHz光变410 d,即τ_(4.8-8)=410 d;4.8 GHz光变延迟14.5 GHz光变440 d,τ_(4.8-14.5)=440 d;8 GHz光变延迟14.5 GHz光变30 d,即τ_(8-14.5)=30 d;通过7个blazar天体的多波段相关分析,和离散相关函数(Discrete Correlation Function,DCF)方法相比,利用TDCF方法获得时间延迟是更加合理的.     

A Study of Solar Radio Bursts with Fine Structures during Flare/CME Events

We have selected 27 solar microwave burst events recorded by the Solar Broadband Radio Spectrometer (SBRS) of China, which were accompanied by M/X class flares and fast CMEs. A total of 70.4% of radio burst events peak at 2.84 GHz before the peaks of the related flares’ soft X-ray flux with an average time difference of about 6.7 minutes. Almost all of the CMEs start before or around the radio burst peaks. At 2.6?–?3.8 GHz bandwidth, 234 radio fine structures (FSs) were classified. More often, some FSs appear in groups, which can contain several individual bursts. It is found that many more radio FSs occur before the soft X-ray maxima and even before the peaks of radio bursts at 2.84 GHz. The events with high peak flux at 2.84 GHz have many more radio FSs and the durations of the radio bursts are independent of the number of radio FSs. Parameters are given for zebra patterns, type III bursts, and fiber structures, and the other types of FSs are described briefly. These radio FSs include some special types of FSs such as double type U bursts and W-type bursts.     

Are Homologous Radio Bursts Driven by Solar Post-Flare Loops？

Three particularly complex radio bursts (2001 October 19, 2001 April 10 and 2003 October 26) obtained with the spectrometers (0.65-7.6GHz) at the National Astronomical Observatories, Chinese Academy of Sciences (NAOC, Beijing and Yunnan) and other in- struments (NoRH, TRACE and SXT) are presented. They each have two groups of peaks occurring in different frequency ranges (broad-band microwave and narrow-band decimeter wavelengths). We stress that the second group of burst peaks that occurred in the late phase of the flares and associated with post-flare loops may be homologous radio bursts. We think that they are driven by the post-flare loops. In contrast to the time profiles of the radio bursts and the images of coronal magnetic polarities, we are able to find that the three events are caused by the active regions including main single-bipole magnetic structures, which are associated with multipole magnetic structures during the flare evolutions. In particular, we point out that the later decimetric radio bursts are possibly the radio counterparts of the homologous flares (called "homologous radio bursts" by us), which are also driven by the single-bipole mag- netic structures. By examining the evolutions of the magnetic polarities of sources (17GHz), we could presume that the drivers of the homologous radio bursts are new and/or recurring appearances/disappearances of the magnetic polarities of radio sources, and that the triggers are the magnetic reconnections of single-bipole configurations.     

Wide-band average spectra of solar radio bursts

Peak flux spectra of solar radio bursts in a wide frequency band have been statistically determined for different morphological types of bursts, for various ranges of magnetic field of the burst-associated sunspots and also for the bursts occurring in the central and limb region of the solar disk. Important results obtained are: (i) The generalised spectra have two peaks, one near to meter-wave and the other in the centimeter-wave region, the former peak being more pronounced than the latter; (ii) identical spectral shape is observed for the great and impulsive types and also for GRF and PBI types of bursts; (iii) the radio emission intensity is relatively higher in the central part than that in the limb part of the solar disk for frequencies 1–10 GHz, while the reverse is true for frequencies 0.245–1 GHz and 10–35 GHz; (iv) the optical depth of the absorbing layer above the source of a burst is found to be the same for meter to centimeter-wavelength bursts, implying that the radio sources in this wide band have uniform characteristics with respect to optical thickness; (v) in case of simultaneous emission in the dekameter to X-ray band, most of the decimetric bursts are seen to be very prompt and coincident with the associated flare's starting time. The interpretations of the obtained spectra give an insight into the possible generation mechanisms, pointing to the location of the source region in the solar atmosphere.     

Broadband Radio Bursts and Fine Structures during the Great Solar Event on 14 July 2000

25 MHz–7.6 GHz global and detailed (fine structure – FS) radio spectra are presented, which were observed in the NOAA 9077 active region for the Bastille Day (14 July 2000) flare at 10:10–11:00 UT. Besides broadband radio bursts, high-resolution dynamic spectra reveal metric type II burst, decimetric type IV burst and various decimetric and microwave FSs, such as type III bursts, type U bursts, reverse-slope (RS)-drifting burst, fiber bursts, patch and drifting pulsation structure (DPS). The peak-flux-density spectrum of the radio bursts over the range 1.0–7.6 GHz globally appears as a U-shaped signature. Analyzing the features of backbone and herringbones of the type II burst, the speeds of shock and relevant energetic electron beams were estimated to be 1100 km s⁻¹ and 58 500 km s⁻¹, respectively. Also the time sequence of the radio emission is analyzed by comparing with the hard X-rays (HXRs) and the soft X-rays (SXRs) in this flare. After the maxima of the X-rays, the radio emission in the range 1.0–7.6 GHz reached maxima first at the higher frequency, then drifted to the lower frequency. This comparison suggested that the flare included three successive processes: firstly the X-rays rose and reached maxima at 10:10–10:23 UT, accompanied by fine structures only in the range 2.6–7.6 GHz; secondly the microwave radio emission reached maxima accompanied by many fine structures over the range 1.0–7.6 GHz at 10:23–10:34 UT; then a decimetric type IV burst and its associated FSs (fibers) in the range 1.0–2.0 GHz appeared after 10:40 UT.     

微波Ⅲ型爆发的观测特征

统计分析了国家天文台2．6-3．8 GHz高时间分辨率射电动态频谱仪在23周峰年期间(1998．4—2003．1)观测到的266个III型爆发．对这些事件的频率漂移、持续时间、偏振、带宽、开始和结束频率做了详细分析．开始和结束频率的统计分析表明,开始频率在一个非常大的范围,从小于2．6 GHz到大于3．8 GHz,而结束频率的截止区相对集中,从2．82-3．76 G．Hz．这些现象说明,电子加速的高度相当分散,在观测频率范围内具有正、负漂移率的III型爆发数基本相等,这可能意味着被加速的向上和向下传播的电子束在2．6—3．8 GHz范围有相同的比例．统计结果表明,微波III型爆发的辐射机制主要是等离子体辐射和电子回旋脉泽辐射过程．     

太阳射电快速精细结构的日面分布

对云南天文台“四波段太阳射电高时间分辨率同步观测系统”自１９８９年１２月—１９９４年１月期间观测到的１００个射电爆发和与其共生的２９个快速精细结构在日球和日面的经度分布做了统计,并做了初步的分析和讨论。     

Solar microwave bursts as indicators of the occurrence of solar proton emission

A study has been made of the relation of 19 GHz( = 1.58 cm) solar radio bursts to solar proton emission, with particular reference to the usefulness of relatively long duration bursts with intensities exceeding 50% of the quiet Sun flux (or exceeding 350 × 10^–22 W m^–2 Hz^–1) as indicators of the occurrence of proton events during the four years from 1966–69. 76 to 88% of such bursts are directly associated with solar protons and 60 to 85% of the moderate to large proton events in the four year period could have been predicted from these bursts. The complete microwave spectra of the proton events have also been studied, and have been used to extend the results obtained at 19 GHz to other frequencies, particularly in the 5–20 GHz band. The widely used frequency of 2.8 GHz is not the optimum frequency for this purpose since proton events have a minimum of emission in this region. Most of the radio energy of proton events is at frequencies above 10 GHz. The radio spectra of proton events tend to peak at higher frequencies than most non-proton events, the overall range being 5 to 70 GHz, with a median of 10–12 GHz and a mean of 17 GHz.On leave from the Radio and Space Research Station, Slough, England, as 1969–1970 National Research Council-National Academy of Sciences Senior Post-Doctoral Research Associate at AFCRL.     

A model for solar radio pulsations at short centimetric band

In this paper, the observed solar radio pulsations during the bursts at 9.375 GHz are considered to be excited by some plasma instability. Under the condition of the conservation of energy in the wave-particle interaction, the saturation time of plasma instabilities is inversely proportional to the initial radiation intensity, which may explain why the repetition rate of the pulsations is directly proportional to the radio burst flux at 9.375 GHz as well as 15 GHz and 22 GHz. It is also predicted that the energy released in an individual pulse increases with increasing the flux of radio bursts, the modularity of the pulsations decreases with increasing the flux of radio bursts, these predictions are consistent with the statistical results at 9.375 GHz in different events. The energy density of the non-thermal particles in these events is estimated from the properties of pulsation. For the typical values of the ambient plasma density (10⁹ cm^–3) and the ratio between the nonthermal and ambient electrons (10^–4), the order of magnitude of the energy density and the average energy of the nonthermal electrons is 10^–4 erg/cm³ and 10 kev, respectively. It is interesting that there are two branches in a statistical relation between the repetition rate and the radio burst flux in a special event on March 11–17, 1989, which just corresponds to two different orders of magnitude for the quasi-quantized energy released in these five bursts. This result may be explained by the different ratios between the thermal and the nonthermal radiations.     

High-resolution observations of solar radio bursts with multi-element compound interferometers at 3.75 and 9.4 GHz

High-resolution observations of solar radio bursts made simultaneously with multi-element compound interferometers at 3.75 and 9.4 GHz are presented.Preliminary results are: (1) The burst of December 16, 1967 showed a change in polarization distribution in the radio source, which suggests a magnetic field change in the source. (2) The existence of the multi-source burst is also confirmed at 3.75 GHz. (3) The source size of the impulsive burst is estimated to be 0.'5. (4) Among the GRF bursts there seem to be two kinds; one has a large angular size and the other has a small one.A brief discussion is given of the burst of December 16, 1967.     

Time Lags between the 22 and 37 GHz Bursts of 48 Radio-loud AGNs

Based on the light curves at 22 and 37 GHz from the Metsahovi monitoring pro-gram, we investigate the time lags between the two radio bands for 48 radio-loud AGNs. DCF and ZDCF analyses are applied to the data. Our results show that there is a strong correlation between the two radio frequencies for all the sources, with the variations in the light curvesat 37 GHz leading the ones at 22 GHz in general. There is no obvious differences between different sub-class AGNs as regards the time lag. In two sources, it was found that the bursts at the lower frequency lead the ones at the higher frequency. One possible explanation is that electron acceleration dominates the light curve until the radiation reaches the maximum. Some sources, such as 3C 273, 3C 279, 3C 345 and 3C 454.3, have good enough data, so we can calculate their lags burst-by-burst. Our calculations show that different outbursts have dif- ferent lags. Some bursts have positive lags, most of bursts have no clear lags, and a few have negative lags. This result means that different bursts are triggered by different mechanisms, and the interpretation for the result involves both an intrinsic and a geometric mechanism. The positive lags are well consistent with the shock model, and we use these lags to calculate the typical magnetic field strength of the radiating region.