Microlensing variability in time-delay quasars

This is the authors' abstract. We don't add key points for this paper.

We have searched for microlensing variability in the light curves of five gravitationally lensed quasars with well-determined time delays: SBS 1520+530, FBQ 0951+2635, RX J0911+0551, B1600+434 and HE 2149-2745. By comparing the light curve of the leading image with a suitably time offset light curve of a trailing image we find that two (SBS 1520+530 and FBQ 0951+2635) out of the five quasars have significant long-term (~years) and short-term (~100 days) brightness variations that may be attributed to microlensing. The short-term variations may be due to nanolenses 10⁻⁴-10⁻³~M_, relativistic hot or cold spots in the quasar accretion disks, or coherent microlensing at large optical depth.