Recurrence of the blue wing enhancements in the high ionization lines of   SDSS 1004+4112 A
  We present integral field spectroscopic observations of the quadruple-lensed QSO SDSS 1004+4112 taken with the fiber system INTEGRAL at the William Herschel Telescope on 2004 January 19. In May 2003 a blueward enhancement in the high ionization lines of SDSS 1004+4112A was detected and then faded. Our observations are the first to note a second event of similar characteristics less than one year after. Although initially attributed to microlensing, the resemblance among the spectra of both events and the absence of microlensing-induced changes in the continuum of component A are puzzling. The lack of a convincing explanation under the microlensing or intrinsic variability hypotheses makes the observed enhancements particularly relevant, calling for close monitoring of this object. 
P. Gomez-Alvarez, E. Mediavilla, J. A. Munoz, S. Arribas, S.F.   Sanchez, A. Oscoz, F. Prada, M. Serra-Ricart