The massive eclipsing binary system IU Aurigae is re-analyzed in the context of new photometric observations and an improved treatment of its long-term period changes (O-C diagram) derived from new times of minima. The best-fit of the O-C curve reveals that the third component is orbiting around the system with a period of 293.3 days in a highly eccentric orbit (e = 0.62). A solution of the most recent UBV light curves obtained during 1997/1998 showed a third light contribution of ≈23% and

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... nuation of the orbital plane precession of IU Aurigae. Since the revised mass of the third component deduced from the analysis of the O-C curve of m 3 = 14.2 M would imply a larger fraction of third light than suggested by the value of 23% derived from the light curve analysis, the third body is possibly composed of two components. A q-search test applied to the UBV light curves yields a minimum χ 2 value at q = 0.67 ± 0.02, which confirms previous photometric and spectroscopic solutions. Article published by EDP Sciences and available at