The MACHO project LMC variable star inventory. X. The R Coronae Borealisstars

We report the discovery of eight new R Coronae Borealis (RCB) stars in the Large Magellanic Cloud (LMC) using the MACHO project photometry database. T he discovery of these new stars increases the number of known RCB stars in the LMC to thirteen. We have also discovered four stars similar to the Gala ctic variable DY Per. These stars decline much more slowly and are cooler t han the RCB stars. The absolute luminosities of the Galactic RCB stars are unknown since there is no direct measurement of the distance to any Galacti c RCB star. Hence, the importance of the LMC RCB stars. We find a much larg er range of absolute magnitudes (M-V = -2.5 to -5 mag) than inferred from t he small pre-MACHO sample of LMC RCB stars. It is likely that there is a te mperature-M, relationship with the cooler stars being intrinsically fainter . Cool (similar to 5000 K) RCB stars are much more common than previously t hought based on the Galactic RCB star sample. Using the fairly complete sam ple of RCB stars discovered in the MACHO fields, we have estimated the like ly number of RCB stars in the Galaxy to be similar to 3200. The SMC MACHO f ields were also searched for RCB stars, but none were found.