Microlensing signatures in spectra of quasars:X-ray radiation

摘要

Gravitational microlensing is a very useful tool for investigating the innermost part ofquasars, especially for studying a relativistic accretion disk around a massive black hole (BH)supposed to exist in the center of every quasar. Here we present a short overview of our recentinvestigations of the gravitational microlensing influence on detected X-ray radiation from accretiondisks of quasars. We set our focus to the analysis of the Fe Ka spectral line and the X-ray continuumvariations due to gravitational microlensing. The disk emission was analyzed by numerical simulations, based on a ray-tracing method in aKerr metric, taking into account only photon trajectories reaching the observer's sky plane. The in-fluence of microlensing on a standard accretion disk was studied using three types of a microlensingmodel: point-like microlens, straight-fold caustic and quadruple microlens (microlensing pattern). Our results show that gravitational microlensing can produce significant variations and amplifi-cations of the Fe Ka line and X-ray continuum flux and that even very small mass objects couldproduce such changes. These deformations of the X-ray radiation depend on both the disk and mi-crolens parameters and they are significantly larger than the corresponding effects on the opticaland UV emission lines and continua, due to the smaller dimensions of the X-ray emitting region.Although gravitational microlensing is an achromatic effect, it can induce wavelength dependentvariations of the X-ray continuum.