X-ray/UV/optical Variability and Mapping the Inner Structures of Active Galactic Nuclei.

来自活动星系核（AGN）的紫外线和光学变异性的起源尚不清楚。这可能是由于非常接近中心超大质量黑洞（SMBH）的x射线辐射被周围的吸积盘和宽线区域（BLR）气体再处理所致。另一种可能是由于盘内吸积速率的波动引起的。这些可能性可以通过测量x射线发射与紫外和光学波段发射之间的时间滞后来测试。不同的物理场景导致不同的时间滞后模式。在再处理方案中，滞后量绘制出吸积盘的温度结构和周围气体的几何形状，这一过程被称为“混响映射”。这些结构太小，无法通过直接成像或任何其他方法来绘制。南安普顿是世界上主要的AGN变异性研究小组之一，我们领导了许多最大的x射线/紫外线/光学监测项目，例如使用雨燕多波段天文台和xmm -牛顿x射线/紫外线天文台。特别是，一个巨大的Swift观测项目将在2018年初完成，这对新学生来说是理想的时机。目前的项目包括观测和计算机建模。成功的学生将分析这些世界领先的数据集，绘制出AGN的内部结构，并建立一个吸积盘和BLR气体预期发射的计算机模型。通过观测与理论的比较，我们将确定AGN的内部几何形状，包括x射线源的几何形状和吸积盘内部的几何形状。

The origin of UV and optical variability from Active Galactic Nuclei (AGN) is not well understood. It may be caused by reprocessing of X-ray emission, coming from very near to the central supermassive black hole (SMBH), by the surrounding accretion disc and broad line region (BLR) gas. Alternatively it might be caused by accretion rate fluctuations in the disc. These possibilities can be tested by measuring the time lags between the X-ray emission and the emission in the UV and optical bands. Different physical scenarios result in different time lag patterns. In the reprocessing scenario, the lags map out the temperature structure of the accretion disc and the geometry of the surrounding gas, in a process known as 'reverberation mapping'. These structure are far too small to map by direct imaging or any other method.Southampton is one of the major world research groups in the study of AGN variability and we lead many of the largest X-ray/UV/optical monitoring programmes, eg using the Swift multiwaveband observatory and the XMM-Newton X-ray/UV observatory. In particular, a huge observational program with Swift will be complete by early 2018, ideally timed for a new student.The current project consists of both observation and computer modelling. The successful student will analyse these world-leading datasets to map out the inner structures of AGN and will also build a computer model of the expected emission from the accretion disc and BLR gas. By comparing observation with theory we will determine the inner geometry of AGN, including both the X-ray source geometry and that of the inner part of the accretion disc.