共查询到19条相似文献，搜索用时 187 毫秒
1.
分析了１９９３－１９９５年ＢＬ Ｌａｃ、ＯＪ２８７和ＰＫＳ０７３５＋１７８三颗ＢＬ Ｌａｃ天体光变的监测结果,并结合文献上他人发表的资料,发现一些ＢＬ Ｌａｃ天体处于高态时活动性较强,短时标光变频繁发生,而处于低态时活动性较弱,短时标光变很少发生。文中提出活动星系核的相对论性喷流方向会改变,从而导致长期光变;高态是喷流方向与观测者视线夹角较小的表现,而低态则是夹角较大的表现。利用该模型能够解释ＢＬ 相似文献
2.
本介绍一种分析寻找ＢＬＬａｃ天体光变周期的方法,给出了ＢＬＬａｃ天体ＯＪ２８７,ＯＮ２３１,Ｍｒｋ４２１托光变周期。 相似文献
3.
展示活动星系核研究和引力研究中的一些难点,揭示了某些天体的光主存在分形结构的可能性,我们提出了活动星系核的中心黑洞具有某种随机微活动性的假设,该假设在可解释活动星系核的一些观测现象。我们发现Ｗｅｉｅｒｓｔｒａｓｓ函数的分形图形可以用来很地拟合ＯＪ２８７的短时标光变。一个用Ｗｅｉｅｒｓｔｒａｓｓ函数构造的分形曲线与ＯＪ２８７的历史光变的线性相关系数达以了０．７３,我们计算了ＯＪ２８７光变曲线的计盒维 相似文献
4.
用Jurkevich方法分析计算BL Lac天体的光变周期 总被引：1，自引：0，他引：1
本文介绍一种分析寻找ＢＬＬａｃ天体光变周期的方法,给出了ＢＬＬａｃ天体ＯＪ２８７,ＯＮ２３１,Ｍｒｋ４２１的长光变周期．分析计算表明：当观测样品的数据点很多、观测时间很长（大约１００年左右的光学波段数据）、数据样本不少于６个周期并能从光变曲线的两次大振幅中,看出有若干小振幅的周期时,则能用该方法准确地认证和确定其长周期值．这种方法在寻找周期时,对无规律不等间隔的样品数据有较高的灵敏度,而计算方法简捷实用,结果可靠 相似文献
5.
收集了ＢＬＬａｃ天体的有关信息作为前文（Ｆａｎ＆Ｌｉｎ１９９６）的补充,并在文中加入了具有喷流、具有超光速子元和具有高能射线辐射的ＢＬＬａｃ天体表。同时在表１ｃ中列出了ＢＬＬａｃ天体的发射线,对偏振度与大幅光变的统计相关在相对论成束框架下给予了解释。 相似文献
6.
展示活动星系核研究和引力研究中的一些难点,揭示了某些天体的光变存在分形结构的可能性。我们提出了活动星系核的中心黑洞具有某种随机微活动性的假设,该假设可解释活动星系核的一些观测现象。我们发现Ｗｅｉｅｒｓｔｒａｓ函数的分形图形可以用来很好地拟合ＯＪ２８７的短时标光变。一个用Ｗｅｉｅｒｓｔｒａｓ函数构造的分形曲线与ＯＪ２８７的历史光变的线性相关系数达到了０．７３。我们计算了ＯＪ２８７光变曲线的计盒维数,信息维数和关联维数,结果表明,这些维数均大于１。我们研究了两个活动星系核（ＯＪ２８７和３Ｃ３４５）的历史光变,发现在星等和这两个物体滞留在这个星等之下的时间长度的对数之间存在线性关系。这种关系可能源于光变的分形结构。我们提出,空时点及附于该点的一个标架与Ｍｉｎｋｏｗｓｋｉ空间上的一个３阶反对称张量场对应。场中的张量取自于一个固定的张量集合。我们得到了Ｒｉｅｍａｎｎ正则坐标下引力场的一个级数表示式。我们还计算了Ｒｉｃｃｉ张量的线性近似和一级非线性近似。这有利于强引力场下的局部非线性结构分析。期望对于引力的进一步研究,通过非线性科学这门新方法的桥粱,沟通极端天文现象与基本引力相互作用之间的鸿沟 相似文献
7.
云南天文台科技档案室 《天文研究与技术》2002,(2)
1、 ＳＣＩ (科学引文索引 )类论文1 ) ＢＬＬａｃ天体和ＦＲＩ射电星系的统一模型的新论据 =ＮｅｗｅｖｉｄｅｎｃｅｆｏｒｔｈｅｕｎｉｆｉｅｄｓｃｈｅｍｅｏｆＢＬＬａｃｅｒｔａｅｏｂｊｅｃｔｓａｎｄＦＲＩｒａｄｉｏＧａｌａｘｉｅｓ.白金明 ,ＭｙｕｎｇＧｙｏｏｎＬｅｅ .ＡｐＪ,2 0 0 1 ,Ｖｏｌ.54 8,2 4 4 -2 4 8.2 ) ＧｅｖＧａｍｍａ源短时标光变的搜索 =ＳｅａｒｃｈｆｏｒｓｈｏｒｔｖａｒｉａｂｉｌｉｔｙｔｉｍｅｓｃａｌｅｏｆｔｈｅＧｅｖＧａｍｍａ-Ｒａｙ -ＬｏｕｄＢｌａｚａｒｓ.谢光中 ,李开华 ,白金明 ,戴本忠 … 相似文献
8.
大幅、快速光变是ＢＬ Ｌａｃ天体的定义特征之一,光变研究一直是ＢＬ Ｌａｃ天体研究的重要内容。本文对ＢＬＬａｃ天体的光变研究成果和ＢＬ Ｌａｃ天体的基本理论以及一些相关的其它研究方向的成果作了较为全面的总结,指出了目前研究中存在的一些不足或可以进一步发展之处,并对其中的几个问题进行耻研究。 全文共分七章。第一章介绍了光变研究的意义和ＢＬ Ｌａｃ天体光变研究的概况,着重总 相似文献
9.
在收集大量资料的基础上,较为全面的综述了Ｂｌａｚａｒｓ天体的基本观测特征,给出了目前较为完整的ＢＬＬａｃ天体总表。对该类天体的相关理论,多波段相关性,光变周期分析,Ｈｕｂｂｌｅ关系,ＢＬＬａｃ天体的偏振度的变化作了一定研究。并介绍了我们用ＣＣＤ测光和光谱对３Ｃ３４５作准同时性观测的结果,我们讨论了３Ｃ３４５的历史光变曲线和光变周期分析,研究结果表明：３Ｃ３４５具有（１０±０．８）ａ（年）的光变周期,其中心有一个１０６Ｍ⊙的黑洞。Ｊｕｒｋｅｖｉｃｈ方法是一种Ｂｌａｚａｒｓ天体的光变周期分析研究的好方法 相似文献
10.
5个新发现的X选BL Lac天体 总被引：1，自引：0，他引：1
利用ＲＯＳＡＴＶＬＡ方法筛选，从ＲＯＳＡＴＸ射线源中选出了一批新的ＢＬＬａｃ天体和类星体的候选体．１９９６年１２月８日至１７日，利用北京天文台２．１６ｍ望远镜和新从美国引进的ＯＭＲ摄谱仪，对这批新候选体进行了光谱认证．经ＳＵＮ工作站处理，又发现了５个新的Ｘ选ＢＬＬａｃ天体．此外，还对去年作者在ＯＭＲ引进之前发现的ＢＬＬａｃ天体进行了检验，结果发现，去年发现的７个ＢＬＬａｃ天体中，２３２２＋３４３的ＣａＩＩＨ＆Ｋ“Ｂｒｅａｋｓｔｒｅｎｇｔｈ”为２６．９％，稍大于判据２５％，因此，２３２２＋３４３到底是ＢＬＬａｃ天体还是射电星系还有待于进一步测光及偏振观测的验证． 相似文献
11.
OJ 287是存在着剧烈活动的低峰频BL Lac天体,其低频段的能谱与另两个TeV BL Lac天体(0716+714和BL Lacertae)在低频段的能谱很相似,但是切仑科夫望远镜却没能探测到它的TeV射线.利用这3个天体的观测数据,比较它们在22 GHz、37 GHz和B波段的最小光变周期及延迟的异同,进一步寻找没有观测到OJ 287的TeV伽马射线的可能原因.分析结果显示:(1)最小光变周期方面,OJ 287在37 GHz和B波段的周期偏小,在22 GHz,OJ 287与0716+714的结果相当,但与BL Lacertae相比要小很多,OJ 287的周期更短表明其活动性更强,却没有探测到来自OJ 287的TeV伽马射线,这表明OJ 287在TeV波段的辐射与这3个低能波段最小光变周期之间可能没有联系;(2)延迟方面,OJ 287在B波段相对于37 GHz的延迟要长于0716+714,短于BL Lacertae;在37 GHz相对于22 GHz的延迟要短于0716+714,而BL Lacertae在37 GHz相对于22 GHz的时延为负值,表明22 GHz要超前于37 GHz.通过对延迟的比较分析,并没有发现OJ 287与0716+714和BL Lacertae之间存在明显的差异;从能谱来看,很可能是由于OJ 287在TeV波段的能谱较陡造成切仑科夫望远镜没有探测到来自OJ 287的伽马辐射,但TeV能段较陡的能谱对低能段光变的影响目前还不是很清楚. 相似文献
12.
OJ 287 is a BL Lac object which exhibits intense activities of low peak-frequencies. Its energy spectrum in low frequency band is quite similar with those of two other TeV BL Lac objects (i.e., 0716+714 and BL Lacertae). However, the Cerenkov telescope did not detect its TeV rays. By using the observational data of these three heavenly bodies and comparing the discrepan- cies of their minimal periods of light variations and delays at 22 GHz, 37 GHz and B-waveband, we have further investigated the possible reason why the TeV gamma-rays of OJ 287 have not been observed. The results of analyses are as fol- lows. (1) For the minimal periods of light variations, the periods of OJ 287 at 37 GHZ and B-waveband are short. At 22 GHz the results of OJ 287 and 0716+714 are comparable, but the period of OJ 287 is much shorter in comparison with that of BL Lacertae, and this shows that its activity is more intense. However, the TeV gamma-rays of OJ 287 have not been detected, which implies that the radiation of OJ 287 in TeV waveband may have no connection with the minimal periods of light variations in these three low-energy wavebands. (2) In respect of delays, the delay of OJ 287 in the B waveband with respect to 37 GHz is longer than that of 0716+714, but shorter than that of BL Lacertae. Its delay at 37 GHz in respect to 22 GHz is shorter than that of 0716+714. Meanwhile, the delay of BL Lacertae at 37 GHz in respect to 22 GHz is negative, which implies that 22 GHz precedes 37 GHz. Via the comparison and analysis of delays, no obvious differences between OJ 287 and 0716+714 as well as BL Lacertae have been found. On the side of energy spectra, it is quite possible that due to the steep energy spectrum of OJ 287 in TeV waveband, the Cerenkov telescope has not detected the gamma radiation of OJ 287. However, nowadays it is still not clear whether the steep energy spectrum in TeV energy range has some influence on the light variations in low energy realm. 相似文献
13.
耀变体在多个波段的微光变和能谱变化多年来是中外天文观测研究的热点课题.耀变体的微光变于20世纪60年代被发现,20世纪80年代以来发现很多源的微光变具有不同的特性,目前对其物理机制的认识和理论、模型的研究还处于发展阶段.该文总结了7个目前观测最多的耀变体(3C 66A,3C 279,3C 454.3,AO 0235+164,BL Lac,OJ 287,S5 0716+714)在光学波段的微光变和能谱变化的观测历史和最新进展,并对其理论模型作了简单介绍. 相似文献
14.
Recent observations provide strong evidence for the BL Lac object OJ287 exhibiting a 11.6±0.5 yr periodicity with a double-peaked
maxima in its optical flux variations. Several models have been proposed for the optical behavior. The 2005 November outburst
in OJ287 gives us a surprising result since calculation based on the periodicity was predicting such an outburst in late 2006.
Here we suggest a new model, it can not only explain the optical quasi-periodic behavior, but also the radio flares behavior
which is and simultaneous with the optical flares. We propose that OJ287 is a binary pair of super-massive black holes, both
of them creating a jet. The quasi-periodic double peaks would be due to the relativistic beaming effect on the emission coming
from the double helix jets. We used “core flares” to explain the large lags between light curves at different frequencies,
and the assumption of two jets appear to be merged with each other partly in the radio frequency emitting regions provides
a viable interpretation that we can see only a broad maximum which contains two radio flares that we cannot distinguish. 相似文献
15.
《天文和天体物理学研究(英文版)》2017,(8)
We present our optical multi-color monitoring of the BL Lac object OJ 287 from January 2006to December 2012 in the V,R and I bands.A relatively active state in OJ 287 has been found over all monitored epochs,among which the variations of average magnitude in V/R/I bands were measured with ?V=1.956 mag,?R=2.067 mag and ?I=2.115 mag,respectively.No reliable intraday variability is detected,but possible variability is detected on 16 nights.Their relative variation amplitudes fall into the range between 1% and 8%,with the majority between 2% and 4%.No time lags have been detected,but strong correlations exist among light curves in the three wavebands.The bluer-when-brighter trend is dominant over intraday timescales,which supports the shock-in-jet model.When combining with additional V/R band data obtained from SMARTS and the Steward Observatory,we also find a bluer-when-brighter trend over a long-term timescale.Some possible periods of 513,176,36,30,26,17 and 14 d are found in all time-series data sets from 2006 to 2017.Possible explanations about these periods are given. 相似文献
16.
Combining our data for three BL Lac objects obtained in 1993–1995 with other authors' we note that activity is stronger and short timescale variations more frequent during the high than the low state. We propose that the relativistic jet in the AGN may change its orientation with time, and the high state corresponds to smaller angles of inclination to the line of sight, and the low, to larger angles. This explains the difference in behaviour as well as the new phenomenon discovered in the monitoring by Takalo et al. 相似文献
17.
Optically violent variable quasars and BL Lac objects, which form a subclass of active galactic nuclei are termed as Blazars.
Blazars show high degree variation in their flux and polarization in a relatively shorter period of time. They are strong
radio sources with a non-stellar continuum. Most of the BL Lac objects do not show any emission lines though in some cases
very weak lines are observed. They harbour in elliptical galaxies. Some BL Lacs show superluminal motion indicating the flow
of matter at relativistic speeds close to the line of sight. It is likely that the enormous energy produced by these objects
may be due to a massive black hole with an accretion disc system. Some Blazars have been observed to detect short time variations
in their flux and polarization in the visual band. These studies are aimed at understanding the physical processes taking
place in the central engine. Detecting shorter period variations assumes significance as they impose restrictions on the total
volume from where the huge amount of energy is comming out. To date the recorded shortest period variation in visual band
is 6.3 min in OJ 287, a BL Lac object. Attempts are being made to detect shorter period variations, which pose observational
challenges. It is generally accepted that the central engine of AGN harbours a massive blackhole with an accretion disc surrounding
it.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
18.
In the inhomogeneous conical jet model, the electron number den- sity and magnetic ?eld strength have a power-law distribution with the distance from the jet apex. This model can interpret successfully the ?at-spectrum radio radiation from the core regions of active galactic nuclei. But the existing model calculation suits only the situation when the enclosed angle between the moving direction of a jet and the line of sight is very large, hence, we need to build a formula for calculating the radiation of inhomogeneous conical jets with any viewing angles. It is generally believed that the enclosed angle between the di- rection of jet motion and the line of sight is very small in BL Lac objects. With the extended inhomogeneous jet model, we have made ?tting on the observed radio spectra of three BL Lac objects, and obtained the physical parameters, such as the electron number density and magnetic ?eld strength in their jets. The result indicates that the nearest distance of the conical jet from the black hole is determined by the transition frequency of the observed radiation spec- trum, and that the nearest distance between the conical jet and the black hole is approximately the Schwarzschild radius for the three BL Lac objects. 相似文献
19.
The continuum spectrum of OJ 287, like most other BL Lac objects, is featureless- no emission or absorption lines are observed. However, OJ 287 shows variations at different timescales in flux and polarization at various wavelength bands. Using the available variability data one can estimate the sizes of the emission regions in the source from light travel time arguments. We assume the emission mechanism to be synchrotron radiation by high energy electrons with single power law energy distribution. Theoretical synchrotron spectrum in the frequency range 1011–1017
H
z
is compared with the observed spectral shape, obtained from new multifrequency quasi-simultaneous observations, to estimate the lower and upper cut off frequencies. These frequencies are used to obtain theoretical values of the variability timescales and magnetic field in the emission region. We obtain a value of 0.93 G for the magnetic field and 5.184×104
sec for the cooling time from the quiescent continuum spectrum. The shock-in-jet model explains the spectrum where shocks accelerate the particles and amplify the magnetic field in the jet. This timescale is compared with the one obtained from observed short timescale variability (20 minutes) with proper beaming correction. The short timescale variations (200 minutes in the source frame), possibly caused by an additional, flaring, component of the source, are also used to calculate compressed magnetic field. The observed and theoretically estimated variability timescales and the shape of the spectrum suggest that there are more than one emission components in OJ 287. 相似文献