Periodicity of the ejection of superluminal components in 3C345

作     者：Shan-Jie Qian A. Witzel J. A. Zensus T. R Krichbaum S. Britzen Xi-Zhen Zhang 

作者机构：National Astronomical Observatories Chinese Academy of Sciences Beijing 100012 China Max-Planck-Institut für Radioastronomie Auf dem Hügel 69 53121 Bonn Germany 

出 版 物：《Chinese Journal of Astronomy and Astrophysics》 (中国天文和天体物理学报（英文版）)

年 卷 期：2009年第9卷第2期

页      面：137-150页

核心收录：

学科分类：0709[理学-地质学] 07[理学] 0708[理学-地球物理学] 070401[理学-天体物理] 070201[理学-理论物理] 0704[理学-天文学] 0825[工学-航空宇航科学与技术] 0702[理学-物理学] 

基　　金：Max-Planck-Institut fur Radioastronomie (Germany) 

主　　题：radio continuum galaxies -- quasars individual 3C345 

摘      要：The search for periodic behavior in Blazars has been an important subject, which is helpful for providing significant clues to the structure and physical processes of their central energy engine. A binary black hole system has recently been suggested for causing precession of relativistic jets and rotation of the ejection position angle of VLBI knots in superluminal sources. It has been suggested that in QSO 3C345, the ejection direction of the superluminal knots rotates due to the precession of the central engine and thus the ejection position angle of the successive knots shows a periodic behavior. Some authors argue for a period of precession being ～5.6 yr （Abraham ＆ Caproni）, ～8-10 yr （Klare et al.） and ～9.5 yr （Lobanov ＆ Roland）. Applying the helical model proposed by Qian et al. and selecting appropriate parameters to fit the initial trajectories （within 0.3 mas） of all the components （C4 to C10）, we derive the relation between the ejection position angle of the components and their precession phase, and thus find a 6.9-year precession period （4.3 yr in the source frame）, which can fit the ejection position angle of all these superluminal knots well. Since the VLBI observations have covered more than two precession periods, confirmation in one or more future periods would be important. In addition, we emphasize that the initial parts of the trajectories of these knots can be fitted by a common helical pattern （channel） through a precessing of its initial phase. This scenario （or helical precessing model） is different from the usual ballistic precessing model in which the individual superluminal knots move along straight-lines after ejection （Tateyama ＆ Kingham）.