SIGNALS FROM THE EDGE OF THE ABYSS: QUASI-PERIODIC OSCILLATIONS IN ACTIVE GALACTIC NUCLEI

当物质螺旋进入黑洞时，它会升温并发出X射线。来自这个吸积盘的X射线编码了关于物质在高度弯曲的时空区域中如何行为的信息。辐射的可变性是由于一些噪声过程，除此之外，偶尔还有准周期振荡（QPO）。这些QPO的快速时间尺度表明它们必须与非常接近黑洞本身的动态或辐射有关。虽然QPO长期以来一直被观察到的X射线双星盘窝藏恒星质量黑洞，它只是在过去的10年左右的证据已经出现，QPO也存在于活动星系核（AGN），窝藏超大质量黑洞（SMBH）。最近的研究表明，QPO在活动星系核中的存在实际上可能比以前认为的要广泛得多。

As matter spirals onto a black hole, it heats up and emits X-rays. The X-rays from this accretion disc encode information about how matter behaves in the region of highly curved space-time. The variability of the radiation is due to a number of noise processes, in addition to which there are - occasionally - Quasi-periodic oscillations (QPOs). The rapid timescales of these QPOs indicate they must be associated with something dynamic or radiative occurring very close to the black hole itself. Whilst QPOs have long been observed from the discs of X-ray binaries harbouring stellar mass black holes, it is only in the last 10 years or so that evidence has emerged that QPOs are also present in active galactic nuclei (AGN), harbouring supermassive black holes (SMBHs). Recent studies have indicated that the presence of QPOs may in fact be much more widespread in AGN that previously thought.