Long-term optical-infrared color variability of blazars  

作　　者：Bing-Kai Zhang Xiao-Shan Zhou Xiao-Yun Zhao Ben-Zhong Dai 

机构地区：[1]Department of Physics, Fuyang Normal College [2]Department of Physics, Yunnan University

出　　处：《Research in Astronomy and Astrophysics》2015年第11期1784-1800,共17页天文和天体物理学研究（英文版）

基　　金：supported by the National Natural Science Foundation of China (Grant No. 11273008);partly by the Foundation for Young Talents in College of Anhui Province (Grant No. 2012SQRL116)

摘　　要：The long-term optical and infrared color variability of blazars has been investigated with monitoring data from the Small and Moderate Aperture Research Telescope System（SMARTS）. The sample in this study consists of 49 flat spectrum radio quasars（FSRQs） and 22 BL Lacertae objects（BL Lacs）. The fractional variability amplitudes of each source have been calculated in both optical R band and infrared J band. Overall, the variability amplitudes of FSRQs are larger than those of BL Lacs. The results also suggest that the variability amplitude of most FSRQs is larger at a lower energy band（J band） than at a higher one（R band）, but the variability amplitude of BL Lacs is larger at the higher energy band. Both types of blazars display color variation along with variability in brightness. However, they show different variation behaviors in general. In the whole data set, 35 FSRQs exhibit redder-whenbrighter trends, and 11 FSRQs exhibit opposite trends; 11 BL Lacs follow bluer-whenbrighter trends, and seven BL Lacs follow opposite trends. A detailed examination indicates that there are 10 blazars showing redder-when-brighter trends in their low state, and bluer-when-brighter or stable-when-brighter trends in their high state. Some more complicated color behaviors have also been detected in several blazars. The nonthermal jet emission and the thermal emission from the accretion disk are employed to explain the observed color behaviors.The long-term optical and infrared color variability of blazars has been investigated with monitoring data from the Small and Moderate Aperture Research Telescope System（SMARTS）. The sample in this study consists of 49 flat spectrum radio quasars（FSRQs） and 22 BL Lacertae objects（BL Lacs）. The fractional variability amplitudes of each source have been calculated in both optical R band and infrared J band. Overall, the variability amplitudes of FSRQs are larger than those of BL Lacs. The results also suggest that the variability amplitude of most FSRQs is larger at a lower energy band（J band） than at a higher one（R band）, but the variability amplitude of BL Lacs is larger at the higher energy band. Both types of blazars display color variation along with variability in brightness. However, they show different variation behaviors in general. In the whole data set, 35 FSRQs exhibit redder-whenbrighter trends, and 11 FSRQs exhibit opposite trends; 11 BL Lacs follow bluer-whenbrighter trends, and seven BL Lacs follow opposite trends. A detailed examination indicates that there are 10 blazars showing redder-when-brighter trends in their low state, and bluer-when-brighter or stable-when-brighter trends in their high state. Some more complicated color behaviors have also been detected in several blazars. The nonthermal jet emission and the thermal emission from the accretion disk are employed to explain the observed color behaviors.

关 键 词：opposite explain brightness fractional bands magnitude systematically hundreds clearly simultaneous 

分 类 号：P157.7[天文地球—天文学] O734[理学—晶体学]