The role of an accretion disk in AGN variability：（的角色在AGN可变性的一个吸积盘）.pdfVIP

The role of an accretion disk in AGN variability B. Czerny Copernicus Astronomical Center, Bartycka 18, 00-716 Warsaw, Poland 4 associated to Observatoire de Paris, LUTH, 92195 Meudon, France 0 0 Abstract. Optically thick accretion disks are considered to be important 2 ingredients of luminous AGN. The claim of their existence is well supported by p observations and recent years brought some progress in understanding of their e dynamics. However, the role of accretion disks in optical/UV/X-ray variability S of AGN is not quite clear. Most probably, in short timescales the disk repro- 0 cesses the variable X-ray flux but at longer timescales the variations of the disk 1 structure lead directly to optical/UV variations as well as affect, or even create, the X-ray variability pattern. We urgently need a considerable progress in time- 1 dependent disk models to close the gap between the theory and the stream of v data coming from the AGN monitoring. 4 5 2 9 0 1. Introduction 4 0 The broad band spectra of bright AGN clearly show the presence of both hot / h optically thin plasma, responsible for hard X-ray emission, and the relatively p cold plasma, presumably an optically thick accretion disk, dominating the op- - o tical/UV emission. The two components interact radiatively, as proved by the r presence of the so called X-ray reflection component detected for the first tim