Photometric monitoring of the doubly imaged quasar UM673: possible   evidence for chromatic microlensing
  We present the results of two-band CCD photometric monitoring of the gravitationally lensed quasar Q 0142-100 (UM 673).The data, obtained at ESO-La Silla with the 1.54 m Danish telescope in the Gunn i-band (October 1998 - September 1999) and in the Johnson V-band (October 1998 to December 2001), were analyzed using three different photometric methods. The light-curves obtained with all methods show variations, with a peak-to-peak amplitude of 0.14 magnitude in $V$. Although it was not possible to measure the time delay between the two lensed QSO images, the brighter component displays possible evidence for microlensing: it becomes bluer as it gets brighter, as expected under the assumption of differential magnification of a quasar accretion disk 
Th. Nakos, F. Courbin, J. Poels, C. Libbrecht, P. Magain, J. Surdej,   J. Manfroid, I. Burud, J. Hjorth, L. Germany, C. Lidm...