Recurrence of the blue wing enhancements in the high ionization lines of SDSS 1004+4112 A

摘要

We present integral field spectroscopic observations of the quadruple-lensedQSO SDSS 1004+4112 taken with the fiber system INTEGRAL at the William HerschelTelescope on 2004 January 19. In May 2003 a blueward enhancement in the highionization lines of SDSS 1004+4112A was detected and then faded. Ourobservations are the first to note a second event of similar characteristicsless than one year after. Although initially attributed to microlensing, theresemblance among the spectra of both events and the absence ofmicrolensing-induced changes in the continuum of component A are puzzling. Thelack of a convincing explanation under the microlensing or intrinsicvariability hypotheses makes the observed enhancements particularly relevant,calling for close monitoring of this object.