Optical variability of PKS 0736+017
  We present BVR photometric observations of the blazar PKS 0736+017. These observations were carried out with three telescopes in Mexico and two in Spain between December 1998 and April 2003. PKS 0736+017 shows remarkable variation at different timescales and amplitudes. Maximum brightness was detected on December 19, 2001 (B=14.90+/-0.01, V=14.34+/-0.01, and R=13.79+/-0.01). A peculiar tendency to redden with increased brightness was detected throughout our observations. Moreover, in one season a good correlation between flux level and spectral slope is shown. This "anomalous" behaviour cannot be described by common flare models of blazars. The flux vs. spectral slope correlation observed in this and other blazars is worth further study. 
A. Ramirez (1), J.A. de Diego (1), D. Dultzin-Hacyan (1), J.N.   Gonzalez-Perez (2,3) ((1)IA-UNAM, Mexico (2)Universitat Ham...