blazar是活动星系核的一个子类，包括BL Lac天体和平谱射电类星体，这类天体最显著的特征是快速而强烈的光变，这种光变一般用喷流内的激波模型来解释，激波模型预言了blazar在不同波段的光变之间存在时间延迟现象，实际观测中也在X射线、紫外、红外和射电波段的光变中发现了一些时延现象，但在光学波段，只观测到时延的上限。最近，我们在BL Lac天体S5 0716+714的光变中发现了置信度很高的光学波段间的时延现象。我们现在申请的课题，是对一些blazar天体进行多波段的监测，并通过相关性分析搜寻不同波段光变间的时延现象，同时结合光变的时标、光变时的谱变化等，来约束blazar的光变机制和辐射模型，约束辐射区的位置、不同能量的粒子的加速、逃逸和冷却机制，为了解blazar的整体模型提供线索。

Blazar is a subset of active galactic nuclei (AGNs) and can be classified into BL Lac object and flat-spectrum radio quasar (FSRQ). The most prominent property of blazar is its rapid and strong variability, which is generally explained with the shock-in-jet model. The shock model predicted the time delay between the variability at different wavelengths. The time delay has been observed in the X-ray, UV, infrared, and radio wavelengths, but only upper limits have been claimed in the optical domain in the past. Recently, we have detected the time delay in the BL Lac object S5 0716+714 with a high confidence level. Now we propose to carry out multi-wavelength monitoring of some blazars and to search for the inter-band time delay with cross-correlation analyses. The results will be combined with the variability timescale and the spectral change during variation, so as to constrain the variation mechanism and the emission model of blazars, to constrain the spatial location of the emission region and the mechanisms of acceleration, escape, and cooling of the electrons with different energy. These will help us to understand the overall model of blazar.