BL Lac天体CGRaBS J0141-0928的光变特性分析

Analysis of Optical Property of BL Lac Object CGRaBS J0141-0928

欧文斯谷射电天文台(Owens Valley Radio Observatory,OVRO)40 m望远镜的观测数据显示,BL Lac天体CGRaBS J0141-0928在15 GHz射电波段存在剧烈光变。利用LSP(Lomb-Scargle-Periodogram)方法、加权小波Z变换(Weighted Wavelet Z-transform,WWZ)方法和Jurkevich方法分析了CGRaBS J0141-0928的光变周期,结果显示该天体具有约为649天的准周期振荡(Quasi-Periodic OScillation,QPO),置信度为4.4σ,准周期振荡可能由喷流的螺旋运动产生。利用双指数函数拟合其中两个爆发的过程,得到光变时标,进而估算平均多普勒因子为3.8,这表明CGRaBS J0141-0928在射电波段存在显著的聚束效应。利用离散相关函数(Discrete Correlation Function,DCF)方法对射电波段分别与γ射线、光学R波段的光变相关性进行分析发现,光学光变与射电光变有强相关性,且光学光变超前于射电光变(66±40)天。

Observation data from the Owens Valley Radio Observatory(OVRO) 40-meter telescope showed multiple dramatic light variations in the 15 GHz radio band of the blazar CGRaBS J0141-0928. LSP(Lomb-Scargle-Periodogram) method, WWZ method(Weighted Wavelet Z-transform, WWZ) and Jurkevich method are used to analyze the light variable period of CGRaBS J0141-0928. The results show that the object has a light variable period of about 649 days(4.4σ significance level), and its Quasi-Periodic Oscillation(QPO) may be caused by the helical motion of the jet. The brightness temperature, time scale of light variability and Doppler factor are estimated by fitting the processes of two bursts with double exponential function. The Doppler factor estimated by the optical time scale of variability is 3.8, and the results show that CGRaBS J0141-0928 has a significant beaming effect in the radio radiation band. The DCF(Discrete Correlation Function) method is used to analyze the correlation between the radio band and Gamma-ray and optical R band. It is found that there is a strong correlation between optical light variability and radio light variability, and the optical light variability is 66 ± 40 days ahead of the radio variability.