Observational and Theoretical Studies of Variability in Compact Extragalactic Sources

致密河外源变异性的观测和理论研究

• 批准号: 8815848
• 负责人: Alan Marscher
• 金额: --
• 依托单位: Trustees of Boston University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 1989
• 资助国家: 美国
• 起止时间: 1989-02-01 至 1992-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=8815848&HistoricalAwards=false
• 关键词: Observational; Theoretical; Studies; Variability; Compact

The variations observed in compact extragalactic radio sources will be investigated both observationally and theoretically. These variations manifest themselves as changes both in the structure as revealed by very-long baseline interferometry (VLBI)studies and in the total flux density. The VLBI technique will be used to monitor two quasars, 4C39.25 and NRAO 140, which are under going particularly interesting variations which may also lead to new understandings of phenomena previously observed. Investigations of theoretical explanations for the observed variability in quasars and similar sources will be carried out. Models involving shock waves propagating through turbulent regions in relativistic jets appear capable of explaining the general characteristics of the observed variations, especially the frequency dependence of the variability timescales. Numerical calculations of emission patterns and spectra of shocks in turbulent jets will be performed and compared with the observational data. The ultimate goal of the proposed project is to better understand the nature and origin of high-speed compact jets in quasars, and through this the nature of the "central engine" in these objects.

将从观测和理论上对紧凑型河外射电源中观测到的变化进行研究。这些变化表现为超长基线干涉测量 (VLBI) 研究揭示的结构变化和总通量密度变化。 VLBI 技术将用于监测两个类星体 4C39.25 和 NRAO 140，它们正在发生特别有趣的变化，这也可能导致对先前观察到的现象有新的理解。将对观测到的类星体和类似来源的变化进行理论解释研究。涉及通过相对论射流中的湍流区域传播的冲击波的模型似乎能够解释所观察到的变化的一般特征，特别是变化时间尺度的频率依赖性。将对湍流射流中的冲击波谱和发射模式进行数值计算，并与观测数据进行比较。该项目的最终目标是更好地了解类星体中高速紧凑射流的性质和起源，并通过此了解这些物体中“中央引擎”的性质。