Spectral Variability of QSOs in the Optical Band
  A new analysis of the variability of the spectral slope of PG QSOs has been performed, on the basis of recent literature data in the B and R photometric bands. Preliminary results confirm our previous findings concerning the increase of variability with the rest-frame observing frequency. We also find a correlation of the spectral slope with luminosity, consistent with temperature changes of an emitting black body. 
Dario Trevese (1), Fausto Vagnetti (2) ((1) Dipartimento di Fisica,   Universita` di Roma "La Sapienza"; (2) Dipartimento di...