新发现7个X选 BL Lac天体和1个类星体(英文)     

谢光中  W．Brinkmann  茶光伟  SallyLaurent－Muehleisen  张有宏  李开华  曹盛林  白金明  刘富坤 《中国天文和天体物理学报》1996,(3)

利用ROSAT－VLA方法筛选，从ROSATX射线源中选出了19个新BLLac天体和类星体的候选体．在1994年至1996年1月期间，利用北京天文台2．16m望远镜对其中16个进行光谱证认，发现了7个新的X选BLLac天体及一个类星体，类星体的红移值为：z＝0.331±0．0015．  相似文献   

A new investigation on drift of base-line value in geomagnetic observation     

杨冬梅  高玉芬  赵永芬  黄蔚北 《地震学报(英文版)》1997,10(4):507-512

Ａｎｅｗｉｎｖｅｓｔｉｇａｔｉｏｎｏｎｄｒｉｆｔｏｆｂａｓｅ┐ｌｉｎｅｖａｌｕｅｉｎｇｅｏｍａｇｎｅｔｉｃｏｂｓｅｒｖａｔｉｏｎＤＯＮＧ－ＭＥＩＹＡＮＧ（杨冬梅）ＹＵ－ＦＥＮＧＡＯ（高玉芬）ＹＯＮＧ－ＦＥＮＺＨＡＯ（赵永芬）ＷＥＩ－ＢＥＩＨＵＡＮＧ...  相似文献   

利用MUSIC算法分析BL Lac天体S5 0716+714光变周期     

唐洁 《天文学报》2012,53(1):1-8

将基于多重信号分类的MUSIC谱估计算法引入BL Lac天体光变周期分析中.给出了MUSIC算法的基本原理,利用模拟信号检测了算法的频谱分辨率.从大量文献中收集了BL Lac天体S5 0716+714光学V、R、I 3个波段从1994年到2008年的有效观测数据,用MUSIC算法和平均周期图算法分别计算了它们的光变周期,发现存在两个主要光变周期:一个是(3.33±0.08)yr的周期,另一个是(1.24±0.01)yr的周期.对这两种算法的周期估计性能进行了比较,结果表明,MUSIC谱估计算法对样本长度要求较低,具有良好的分辨特性和抗噪声能力,能提高在样本长度较短情况下光变周期分析的准确性.  相似文献   

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

B. Z. Dai  X. H. Li  Z. M. Liu  B. K. Zhang  W. W. Na  Y. F. Wu  J. M. Hao  Y. Xiang  Z. J. Jiang  L. Zhang 《Monthly notices of the Royal Astronomical Society》2009,392(3):1181-1192

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.  相似文献   

Intranight polarization variability in radio-loud and radio-quiet AGN     

Carolin Villforth  Kari Nilsson  Roy Østensen  Jochen Heidt  Sami-Matias Niemi  Janine Pforr 《Monthly notices of the Royal Astronomical Society》2009,397(4):1893-1908

  相似文献   

Unusual optical quiescence of the classical BL Lac object PKS 0735+178 on intranight time-scale     

Arti Goyal    Gopal-Krishna  G. C. Anupama  D. K. Sahu  R. Sagar  S. Britzen  M. Karouzos †  M. F. Aller  H. D. Aller 《Monthly notices of the Royal Astronomical Society》2009,399(3):1622-1632

We present the result of our extensive intranight optical monitoring of the well-known low-energy peaked BL Lac (LBL) object PKS 0735+178. This long-term follow-up consists of R -band monitoring for a minimum duration of ∼4 hours, on 17 nights spanning 11 years (1998–2008). Using the CCD as an N-star photometer, a detection limit of around 1 per cent was attained for the intranight optical variability (INOV). Remarkably, an INOV amplitude of  ≥3 per cent  on hour-like time-scale was not observed on any of the 17 nights, even though the likelihood of a typical LBL showing such INOV levels in a single session of  ≳4  hours duration is known to be high  (∼50 per cent)  . Our observations have thus established a peculiar long-term INOV quiescence of this radio-selected BL Lac object. Moreover, the access to unpublished optical monitoring data of similarly high sensitivity, acquired in another programme, has allowed us to confirm the same anomalous INOV quiescence of this LBL all the way back to 1989, the epoch of its historically largest radio outburst. Here, we present observational evidence revealing the very unusual INOV behaviour of this classical BL Lac object and discuss this briefly in the context of its other known exceptional properties.  相似文献   

Calculating the Light Period of BL Lac Object S5 0716+714 by Wavelet Analysis Method     

Hao-Jing Zhang  Xiong Zhang  Fu-Tong Dong  Yong-Gang Zheng  Ling Tang  Li-Sheng Mao 《Chinese Astronomy and Astrophysics》2009

A kind of wavelet analysis method for identifying the light period of the BL Lac object S5 0716+714 is introduced. The rather complete observed data in the four optical wavebands B, V, R, I are collected, and the long-term light curves based on 10-day averaging are obtained. On these light curves, the periodicity analysis is performed by using a wavelet analysis method. The result demonstrates that the wavelet analysis method is preferable for searching and identifying the light periods of BL Lac objects. From the contour map of the real part of the wavelet transform coefficient, the periodical light variations of the BL Lac object S5 0716+714 can be precisely identified. By analyzing the wavelet variance curves at the 4 wavebands, it is found that the BL Lac Object S5 0716+174 has a stable light period of 1160 days. This result is consistent with the 3.3-year period given by Raiteri et al. It is predicted that the next outburst in this object will happen around the August of 2011.  相似文献   

A Study of the γ-ray and X-ray Radiations of BL Lac Objects     

Hao-jing Zhang  Xiong Zhang 《Chinese Astronomy and Astrophysics》2009

The X-ray and γ-ray flux densities of 18 γ-loud BL Lac objects as well as their average spectral indices of X-ray wave band (1 keV) and γ-ray wave band (>100 MeV) are collected, and the correlations among the various quantities are examined. The results indicate: (1) The X-ray flux density and the γ-ray flux density exhibit rather strong correlations in all the states, high, low or mediate. (2) Between the mean spectral indices in X-ray and γ-ray wave bands there is a comparatively intense anti-correlation. (3) Between the average spectral indices and the X-ray and γ- flux densities there is no evident correlation either in the high or the mediate state. (4) Between the average spectral index of γ-ray wave band and the flux density of X-rays in low state there is a rather strong anticorrelation. Between the mean spectral index of X-ray wave band and the γ-flux density in low state there also exists a weak correlation. The results of our analysis support the viewpoint that both the X-ray and γ-ray emissions of BL Lac objects come from the synchrotron radiation and synchrotron self Compton (SSC) radiation with one and the same distribution of relativistic electrons.  相似文献   

Brightness temperature for 166 radio sources     

Jun-Hui Fan Yong Huang Yu-Hai Yuan Jiang-He Yang Yi Liu Jun Tao Ying Gao Tong-Xu Hua Rui-Guang Lin Jiang-Shui Zhang Jing-Yi Zhang Yi-Ping Qin 《天体物理学报》2009,(7):751-760

Using the database of the University of Michigan Radio Astronomy Observatory （UMRAO） at three radio frequencies （4.8, 8 and 14.5 GHz）, we determined the short-term variability timescales for 166 radio sources. The timescales are 0.15d （2007＋777） to 176.17 d （0528-250） with an average timescale of Atobs = 17.1 4- 16.5 d for the whole sample. The timescales are used to calculate the brightness temperatures, TB. The value of log TB is in the range of log TB = 10.47 to 19.06 K. In addition, we also estimated the boosting factor for the sources. The correlation between the polarization and the Doppler factor is also discussed.  相似文献   

射电源的谱指数     

袁聿海  李娟 《天文研究与技术》2007,4(1):11-20

文章研究了162个射电源,其中包括了47个BL Lacs ,21个galaxies ,94个平谱射电类星体( FSRQs ) ,这些源是通过Michigan大学的26m的射电望远镜观测的。大多数源都包含了3个波段的观测数据:4 .8GHz ,8GHz和14 .5GHz。文中计算了3个子类的平均的流量密度,并且得到了相应的谱指数(αwei) ,αBL=0 .08±0 .28 ,αGAL=-0 .91±0 .32 ,αFSRQ=-0 .14±0 .4。同时也讨论了这些源的射电性质,其中包含了谱指数,流量密度和红移之间的关系,流量密度和谱指数之间的关系。  相似文献