Spectra and Variability of X-ray emission from accreting black holes

研究X射线光谱和黑洞吸积时的辐射时间。当物质福尔斯落在黑洞上时，它会变热并发出高能辐射。研究这种辐射的确切性质可以推断黑洞周围结构的性质。据了解，吸积盘的形成通常会在星系中心的超大质量黑洞中发出紫外线，而在恒星质量黑洞中发出软X射线。然后，这些辐射的一部分被称为日冕的热电子群散射到X射线波长，新的高能天文台，特别是努斯塔，能够拍摄日冕发射到高能截止点的光谱，提供有关电子温度等重要性质的信息。吸积盘还提供了一个表面，光子可以散射，形成原子反射特征。中心黑洞附近的原子线如何被广义相对论效应移动，可以提供有关内部吸积盘及其所在时空的信息。当辐射离开黑洞到达我们时，它穿过热气体云，这些特征可以用来确定黑洞周围气体云的结构。发射也是强烈可变的，不同波段之间的相互变化可以提供它们之间的关系和几何形状的信息。当日冕发射从盘反射时，反射分量的变化预计会显示出相对于直接日冕发射的滞后。这个滞后的大小设定了到圆盘反射区的距离的上限，即光在这段时间内可以传播的距离。结合这些不同的信息来源将允许进一步阐明黑洞周围吸积的细节。

Studying X-Ray spectra and timing of emission from accreting black holes.As matter falls onto black holes, it heats up and emits high energy radiation. Studying the precise nature of this radiation allows inferences to be made about the nature of the structure around the black hole.It has been learnt that an accretion disc forms which typically emits in UV for the supermassive black holes at the centre of galaxies and in soft X-rays for stellar mass black holes.Some of this emission is then scattered to X-ray wavelengths by a population of hot electrons, known as a corona, whose exact nature is unknown.New high-energy observatories, in particular NuSTAR, are able to take spectra of the emission from this corona up to its high-energy cut-off, providing information about important properties such as the temperature of the electrons.The accretion disc also provides a surface off of which photons can scatter, forming atomic reflection features. How atomic lines are shifted by general relativistic effects near the central black hole can provide information about the inner accretion disc and the spacetime in which it resides.As the emission leaves the black hole to reach us, it passes through clouds of hot gas, which imprint absorption features which may be used to determine the structure of the gas clouds around the black hole.The emission is also strongly variable and studying how different bands vary with respect to each other can provide information on their relationship and geometry.When coronal emission is reflected from the disc, changes in the reflected components are expected to show a lag relative to the direct coronal emission. The size of this lag sets an upper bound on the distance to the reflecting region of the disc, given by the distance light can travel in this time.Combining these various sources of information will allow further details of accretion around black holes to be elucidated.