Early-type contact systems in the LMC MACHO database

Two sub-samples of blue, luminous contact systems from among 86 systems dis covered in the LMC by the MACHO project and classified as EB3 have been ana lyzed: a sub-sample of 29 extremely-blue systems (XB) with the observed col ors V - R-C < -0.1 and a sub-sample of 36 moderately-blue (MB) systems with -0.1 < V - R-C < 0. To be so blue, the XB systems must be intrinsically ve ry hot and almost unreddened so that lack of information on reddening is un important for them; their properties offer us a first-time insight into the absolute-magnitude calibration for massive contact binaries. It has been f ound that the LMC systems are apparently not limited by the blue, shea-peri od envelope in the color-period diagram which had been established on the b asis of systems observed in the solar neighborhood, in Galactic open cluste rs and in the sample of Old Disk systems in the direction of the Galactic b ulge. The period-magnitude correlation for the XB systems has a similar slo pe to those established in the absolute-magnitude, B - V and V - I-C based, calibrations for W UMa-type systems.