Separating Intrinsic and Microlensing Variability using Parallax Measurements

In gravitational lens systems with 3 or more resolved images of a quasar, the intrinsic variability may be unambiguously separated from the microlensing variability through parallax measurements from 3 observers when there is no relative motion of the lens masses (Refsdal 1993). In systems with fewer than 3 resolved images, however, this separation is not straightforward. For the purpose of illustration, I make the following simplifications for the one-dimensional case: The observations consist of well-sampled time series of the observed flux F A (t i ) and F B (t i ) at two points in the observer plane. The separation vector of the two points is parallel to the direction of the transverse motion of the source-lens-observer system, and the distance D AB between the observers is known. Furthermore, the distance D AB small compared to the typical length scale of fluctuations in the magnification μ(x).