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

Abstract

We consider the influence of microlensing on different spectral bands of lensed QSOs. We assumed that the emitting X‐ray, ultraviolet (UV) and optical regions are different in size, but that the continuum emission in these spectral bands is originating from an accretion disc. Estimations of the time‐scales for microlensing and flux amplification in different bands are given. We found that the microlensing duration should be shorter in the X‐ray (several months) than in UV/optical emitting region (several years). This result indicates that monitoring of the X‐ray variations in lensed QSOs that show a ‘flux anomaly’ can clarify the source of this anomaly.

Lensing by exotic objects

“…3 The light curves for microlensing by a non-compact object for D = 4 and different sizes of a non-point source. The maximal values of the light curves decrease with increasing source radius, which is chosen as R s = 0.01, 0.03, 0.1, respectively source has a smoothening effect on the variations of amplifications near caustics, similarly to microlensing in gravitationally lensed systems and exoplanet searches [113,114,145,146,146]. One can see that the light curves in Fig.…”

“…The optical depth of microlensing for distant quasars was discussed for different locations of microlenses [109][110][111][112]. An influence of microlensing on spectral lines and spectra in different bands was analyzed in [113,114]. These investigations were inspired by discoveries of microlensing features in the X-ray band for gravitationally lensed systems [115][116][117][118].…”

Theoretical estimations of future polarization observations for exoplanery searches with gravitational microlensing

“…[19,78,79,80], and indeed an exoplanet might be already discovered in the PA-N2-99 event [19]. Since source stars for pixel-lensing towards M31 are basically red giants (and therefore, their typical diameters are comparable to Einstein diameters and the caustic sizes) one has to take into account the source finiteness effect, similarly to microlensing in quasars [12,81,82,83]. As it is well known the amplifications for a finite source and for a point-like source are different because there is a gradient of amplification in respect of a source area.…”

Exoplanetary searches with gravitational microlensing: Polarization issues

“…The extended source effects in gravitational microlensing enable studying the stellar atmospheres through their limb-darkening profiles and by modelling their microlensed spectra, see Loeb & Sasselov (1995); Sasselov (1996) Pixel-lensing towards M31 may provide an efficient tool to search for exoplanets in that galaxy (Chung et al, 2006;Kim et al, 2007;Ingrosso et al, 2009), and indeed an exoplanet might be already discovered in the PA-N2-99 event (Ingrosso et al, 2009). Since source stars for pixel-lensing towards M31 are basically red giants (and therefore, their typical diameters are comparable to Einstein diameters and the caustic sizes) one has to take into account the source finiteness effect, similarly to microlensing in quasars (Agol & Krolik, 1999;Popović et al, 2006;Jovanović et al, 2008;Zakharov, 2009). As it is well known the amplifications for a finite source and for a point-like source are different because there is a gradient of amplification in respect of a source area.…”