X-Ray and Optical Flux Anomalies in the Quadruply Lensed QSO 1RXS   J1131-1231
  Optical and X-ray observations of the quadruply imaged quasar 1RXS J1131-1231 show flux ratio anomalies among the images factors of ~2 in the optical and \~3-9 in X-rays. Temporal variability of the quasar seems an unlikely explanation for the discrepancies between the X-ray and optical flux ratio anomalies. The negative parity of the most affected image and the decreasing trend of the anomalies with wavelength suggest microlensing as a possible explanation; this would imply that the source of optical radiation in RXS J1131 is ~10^4 R_g in size for a black hole mass of ~10^8 M_sun. We also present evidence for different X-ray spectral hardness ratios among the four images. 
Jeffrey A. Blackburne (1), Dave Pooley (2) and Saul Rappaport (1) ((1)   MIT, (2) University of California at Berkeley)