Optical and infrared study of the three quasars OX 169, NRAO 140 and 3C 446.

Results are presented of photometric monitoring of three luminous quasars at optical and IR wavelengths. The observations were designed to sample different time scales from few days to 6 months. The quasars were OX 169, NRAO 140 and 3C 446. OX 169 showed variations of flux in the V and K bands of +40 percent and -20 percent respectively in 18 days. Faster variations were observed in the K flux of NRAO 140 (20 percent in 2 days) followed by smaller amplitude variability of opposite sign in the J and H bands. Only slow variations were observed in 3C 446, of the same sign in all observed bands. The observations imply the presence of several components in the spectra for which physical interpretations are suggested.