THE MACHO PROJECT LARGE MAGELLANIC CLOUD VARIABLE-STAR INVENTORY .4. NEW R-CORONAE-BOREALIS STARS

We report the discovery of two new R Coronae Borealis (RCB) stars in t he LMC using the MACHO project photometry database. The identification of both stars has been confirmed spectroscopically. One is a cool RCB star (T-eff similar to 5000 K), characterized by very strong Swan ban ds of C-2 and violet bands of CN, and weak. or absent Balmer lines, G band, and (CC)-C-12-C-13 bands. The second star is an example of a hot RCB star, of which only three were previously known to exist in the G alaxy and none in the LMC. Its spectrum is characterized by several C II lines in emission. Both stars have shown deep declines of Delta V g reater than or equal to 4 mag in brightness. The new stars are signifi cantly fainter at maximum light than the three previously known LMC RC B stars. The amount of reddening toward these stars is somewhat uncert ain, but both seem to have absolute magnitudes, M(v), similar to 0.5 m ag fainter than the other three stars. Estimates of M(bol) find that t he hot RCB star lies in the range of the other three stars, while the cool RCB star is fainter. The two cool LMC RCB stars are the faintest at M(bol). The discovery of these two new stars brings to five the num ber of known RCB stars in the LMC, and it demonstrates the utility of the MACHO photometric database for the discovery of new RCB stars.