Optical photometry of the eclipsing Large Magellanic Cloud supersoft source CAL 87

Abstract

We present optical photometry of the eclipsing supersoft source CAL 87. These observations comprise long-term data accumulated as a by-product of the MACHO Project, and high-speed, white-light photometry of a single eclipse. We (i) derive an improved ephemeris of T0=HJD 245 0111.5144(3) + 0.44267714(6)E for the time of minimum light, (ii) find the eclipse structure to be stable over a period of ∼4 yr, and (iii) investigate the colour variation as a function of orbital phase. The resolution afforded by the high-speed nature of the white-light observations enables us to see new structure in the light-curve morphology. © 1997 RAS.