Absolute dimensions of the close binary systems V453 Monocerotis and V523 Cassiopeiae

We present multi-colour CCD observations of the low-temperature contact binaries, V453 Mon and V523 Cas. Their light curves are modelled to determine a new set of stellar and orbital parameters. Analysis of mid-eclipse times yields a new linear ephemeris for both systems. A period decrease (dP/dt=2.3x10(-7) days/yr) in V453 Mon is discovered. V523 Cas, however, is detected to show a period increase (dP/dt=9.8x10(-8) days/yr) because of the mass transfer of a rate of 1.1x10(-7) M-aS (TM) yr(-1), from a less massive donor. Using these findings we can determine the physical parameters of the components of V523 Cas to be M (1)=0.76 (3)M (aS (TM)), M (2)=0.39 (2)M (aS (TM)), R (1)=0.74 (2)R (aS (TM)), R (2)=0.55 (2)R (aS (TM)), L (1)=0.19 (3)L (aS (TM)), L (2)=0.14 (3)L (aS (TM)), and the distance of system as 46(9) pc.