2003A&A...412L..25V

UBV and BVR photometry of η Car during the 2003.5 low-excitation event - the considered periastron passage of a binary - is presented. The light and colour curves show a number of features, which were also seen at previous periastron passages: a light maximum of long duration with a superimposed flare-like event which is temporarily interrupted by an eclipse-like dip, and a steep decline in the U-B color index. The R brightness reached a minimum at the time of mid X-ray totality, probably implying that the Hα emission line reached a minimum. The source of the optical flare-like event is probably not the same as the one causing the the X-ray radiation. It is tempting to consider the epoch of the R minimum and the mid- X ray totality - which roughly coincides with the UBV minimum - as the central moment of the 2003.5 low-excitation event.