2 Photometry

An ephemeris for the eclipsing binary QZ Car valid at present was derived using the more recent minima (see Table 4), which will be used for the phasing of the eclipsing system B throughout this paper:

$${\rm Prim.\, Min. = hel.\, JD}\,\, 2448687.16 + 5\hbox{$.\!\!^{\rm d}$ }9991 \cdot E.$$ (1)

Due to the particular, near integer day period of the eclipsing binary, no well-covered light curve obtained with ground-based telescopes exists. There are only very few measurements published by Walker & Marino (1972) and Moffat (1977). The present authors measured the star in UBV with the 50 cm ESO telescope at La Silla in 1992 and 1993; the light curve, however, also appears to be not suitable for solution. Some data were added by Christie (1998). In Fig. 1 these data are shown. Since a possible variability of the comparison star HD 93131 could not be excluded, our data were calibrated in terms of an all-sky photometry. Intrinsic variability of QZ Car is supported by these data, the type of which is in general agreement with the measurements by Walker & Marino and Moffat.

Perhaps the best quality light curve by now was obtained by HIPPARCOS (ESA 1997), see Fig. 2. Even this curve is affected by a rather large scatter, which might be due to the close vicinity of similarly bright stars; also short-term intrinsic variability of the star itself could contribute to the photometric scattering. Note that the best fit between photometry in the V bandpass and photometry by HIPPARCOS is obtained for $H_{\rm p}~=~V+0.01$.

Figure 2: HIPPARCOS measurements phased according to ephemeris (1). Data of lower accuracy are plotted as opencircles