[en] We present the analysis of single epoch long slit spectra of the three brightest images of the gravitationally lensed system J1131-1231. These spectra provide one of the clearest observational evidence for differential micro-lensing of broad emission lines (BELs) in a gravitationally lensed quasar. The micro-lensing effect enables us: (1) to confirm that the width of the emission lines is anti-correlated to the size of the emitting region; (2) to show that the bulk of Fe II is emitted in the outer parts of the Broad Line Region (BLR) while another fraction of Fe II is produced in a compact region; (3) to derive interesting informations on the origin of the narrow intrinsic Mg II absorption doublet observed in that system.
The authors thank Revista Mexicana de Astronomía y Astrofísica : Universidad Nacional Autónoma de México. Instituto de Astronomía for their deposit authorization. The original publication is available at http://www.astroscu.unam.mx/~rmaa/