X-RAY MONITORING OF GRAVITATIONAL LENSES WITH CHANDRA
We present Chandra monitoring data for six gravitationally lensed quasars: QJ 0158−4325, HE 0435−1223, SDSS 0924+0219, SDSS 1004+4112, HE 1104−1805, and Q 2237+0305. X-ray microlensing variability is detected in all six lenses with high confidence. We furthermore detect energy-dependent microlensing in HE 0435−1223, SDSS 0924+0219, SDSS 1004+4112, and Q 2237+0305. Through a detailed spectral analysis for each lens we find that simple power-law models plus Gaussian emission lines give good fits to the spectra. We detect intrinsic spectral variability in two epochs of Q 2237+0305, and differential absorption between images in QJ 0158−4325 and Q2237+0305. We also detect the Fe Kα emission line in all six lenses, and the Ni xxvii Kα line in two images of Q 2237+0305. The rest-frame equivalent widths of the Fe Kα lines are measured to be 0.4–1.2 keV, significantly higher than those measured in typical active galactic nuclei of similar X-ray luminosities. This suggests that the Fe Kα emission region is more compact or centrally concentrated than the continuum emission region.