Amplification and variability of the AGN X‐ray emission due to microlensing

Abstract

We consider the contribution of microlensing to the AGN Fe Kα line and X-ray continuum amplification and variation. To investigate the variability of the line and X-ray continuum, we studied the effects of microlensing on quasar X-ray spectra produced by crossing of a microlensing pattern across a standard relativistic accretion disk. To describe the disk emission we used a ray tracing method considering both metrics, Schwarzschild and Kerr. We found that the Fe Kα and continuum may experience significant amplification by a microlensing event (even for microlenses of very small mass). Also, we investigate a contribution of microlensing to the X-ray variability of high-redshifted QSOs, finding that cosmologically distributed deflector may contribute significantly to the X-ray variability of high-redshifted QSOs (z > 2).

Microlensing of the X-ray, UV and optical emission regions of quasars: simulations of the time-scales and amplitude variations of microlensing events

“…Microlensing can result in flux anomalies in the sense that different image flux ratios are observed in different spectral bands (Popović & Chartas 2005; Popović et al 2006b). As shown in Figs 2–6, the amplification in the X‐ray band is larger and lasts shorter than it does in the UV and optical bands.…”

“…Recent observational and theoretical studies suggest that gravitational microlensing can induce variability not only in optical light, but also in the X‐ray emission of lensed QSOs (Popović et al 2001; Chartas et al 2002; Dai et al 2003; Chartas et al 2004; Dai et al 2004; Jovanović 2006; Popović et al 2003a, 2003b, 2006a,b). Variability studies of QSOs indicate that the size of the X‐ray emitting region is significantly smaller (∼ several light‐hours), than the optical and ultraviolet (UV) emitting regions (∼ several light‐days).…”

Influence of gravitational microlensing on broad absorption lines of QSOs: The case of the Fe Kα line

“…For some specific microlensing event one can model the corresponding magnification map using numerical simulations based on ray-shooting techniques (see e.g. Popović et al, 2006b;Jovanović et al, 2008;Jovanović and Popović, 2009, and references therein), in which the rays are shot from the observer to the source, through a randomly generated star field in the lens plane. These light rays are then collected in pixels in the source plane, and the number of rays in one pixel is proportional to the magnification due to microlensing at this point in the source plane.…”

Fast simulations of extragalactic microlensing

“…Wambsganss (1990) combined the microlenses in groups with larger sizes for more distant stars in a hierarchical tree code. Finally, Shalyapin (1995) proposed the solution of the twodimensional Poisson equation and explored models with high star density (Popovic et al 2006).…”