Microlensing in the Q0957 + 561 gravitational mirage

Analysis of the 10 yr record from monitoring the continuum brightness of Q0957 + 561 A, B shows a systematic increase of the B relative to the A component. The B brightness has leveled off in the last 2 yrs at a value 32% higher than would be predicted from the ratio of Mg II 2798 A emission line strengths. We take this to be the signature of microlensing by a star or stars in the lens galaxy. We also present new data on the emission line ratio seen in the two image components. Correctly phased data show this ratio to be 0.75 +/- 0.02 in good agreement with previously published estimates from unphased optical data. Comparison of the profiles of the correctly phased emission lines gives only marginally useful limits on the effects of microlensing on the QSO's broadline emission regions.

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