标题： 双频段对双重射电星系的研究 显示英文标题

标题： A Multifrequency Study of Double-Double Radio Galaxies

摘要： 活动星系核中周期性活动的一个显著例子是双双射电星系（DDRGs），它们具有两对方向相反的射电瓣，来自不同活动周期。 我们以DDRG J1453+3308为例进行说明，使用GMRT和VLA在宽频率范围内的观测可以用来确定内瓣和外瓣的光谱，估计它们的光谱年龄，估计周期性活动的时间尺度，并检查两个活动周期中注入光谱的任何差异。 低频GMRT观测还表明，DDRGs和三双射电星系相当罕见。 显示英文摘要

摘要： One of the striking examples of episodic activity in active galactic nuclei are the double-double radio galaxies (DDRGs) with two pairs of oppositely-directed radio lobes from two different cycles of activity. We illustrate, using the DDRG J1453+3308 as an example, that observations over a wide range of frequencies using both the GMRT and the VLA can be used to determine the spectra of the inner and outer lobes, estimate their spectral ages, estimate the time scales of episodic activity, and examine any difference in the injection spectra in the two cycles of activity. Low-frequency GMRT observations also suggest that DDRGs and triple-double radio galaxies are rather rare.