Light variations of massive stars (alpha Cygni variables). XI. The behaviour of the S Doradus type stars AG Carinae and HR Carinae near minimum light.

VBLUW photometry of the microvariations of AG Car (1987/1988) and HR Car (1981/1982 and 1987/1988) and of the macrovariations of HR Car (1984/1987) is presented and discussed. Both objects, although at or close to minimum light, show small S Dor eruptions corresponding to an increase in the mass loss rate of about 20 percent. The time scale of these eruptions, presumably 0.5-1 yr, is thus much longer than the quasi-periods of the intrinsic variations. Therefore, independency between both phenomena is suggested. The reddening and luminosity of HR Car is discussed, as well as its temperature. A tentative estimation of T(eff) based on the fluctuation in the color indices, amounts to about 14,000 K + or - 2000 K. The absolute bolometric magnitude = -9.5 m.