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Time Lags between the 22 and 37 GHz Bursts of 48 Radio-loud AGNs
Authors:Wen-Guo Deng  Jin-Ming Bai  Li Zhang  Xian Yang
Institution:[1]National Astronomical Observatories/Yunnan Observatory, Chinese Academy of Sciences, Kunming 650011; [2]Physics Department, Yunnan University, Kunming 650091
Abstract:Based on the light curves at 22 and 37 GHz from the Metsahovi monitoring pro-gram, we investigate the time lags between the two radio bands for 48 radio-loud AGNs. DCF and ZDCF analyses are applied to the data. Our results show that there is a strong correlation between the two radio frequencies for all the sources, with the variations in the light curvesat 37 GHz leading the ones at 22 GHz in general. There is no obvious differences between different sub-class AGNs as regards the time lag. In two sources, it was found that the bursts at the lower frequency lead the ones at the higher frequency. One possible explanation is that electron acceleration dominates the light curve until the radiation reaches the maximum. Some sources, such as 3C 273, 3C 279, 3C 345 and 3C 454.3, have good enough data, so we can calculate their lags burst-by-burst. Our calculations show that different outbursts have dif- ferent lags. Some bursts have positive lags, most of bursts have no clear lags, and a few have negative lags. This result means that different bursts are triggered by different mechanisms, and the interpretation for the result involves both an intrinsic and a geometric mechanism. The positive lags are well consistent with the shock model, and we use these lags to calculate the typical magnetic field strength of the radiating region.
Keywords:galaxies: active - galaxies: individual (3C 273  3C 279  3C 345  3C 454  3) -methods: data analysis
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