1994A&AS..103...33S

According to models of gravitational microlensing, the brightness of a quasar image will vary depending on the size of the quasar among other quantities. When observing a quasar through different filters this can lead to the determination of the quasar size in the different wavelengths relative to each other. Observations of the quadruple quasar Q2237+031 indicate that at least one of the images is affected by microlensing. Furthermore, the brightness variation of the continuum in this image is found to be larger than the emission line variability. This result agrees with standard quasar models predicting that the emission line region is much larger than the central engine coupled with microlensing models predicting that a larger source size produces smaller brightness variations. Comparing the results with models of microlensing, shows that the emission line region most likely is at least eight times as large as the continuum region.