Refinement of third body parameters and new photometric results for the early-type multiple system IU Aurigae

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 continuation 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 $m_3=14.2$ $M_{\odot}$ 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 ${\chi^2}$ value at $q=0.67 \pm 0.02$, which confirms previous photometric and spectroscopic solutions.