The Nature of the Companion to the Eclipsing Overtone Cepheid MACHO 81.8997.87

The lightcurve of the Large Magellanic Cloud (LMC) variable star MACHO 81.8997.87 shows evidence for photometric variations due to both stellar pulsation, with a 2.035 day period, and eclipsing behavior, with an 800.4 day period. The primary star of the system has been identified as a first-overtone Cepheid but the nature of the secondary star has not been determined. Here we present multicolor BVI photometry of a primary eclipse of the system and fit a model to the complete lightcurve to produce an updated set of elements. These results are combined with 2MASS JHK photometry to give further insight into the identity of the companion star. We find that the companion is most consistent with a late-K or an early-M giant but also that there are a number of problems with this interpretation. The prospects for future observations of this system are also discussed.