We report the discovery of two new R Coronae Borealis (RCB) stars in the
Large Magellanic Cloud (LMC) using the MACHO project photometry database. The
identification of both stars has been confirmed ...spectroscopically. One is a
cool RCB star (T_eff about 5000 K) characterized by very strong Swan bands of
C_2 and violet bands of CN, and weak or absent Balmer lines, G-band and 12C-13C
bands. The second star is an example of a hot RCB star of which only 3 were
previously known to exist in the Galaxy 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 > 4 mag in brightness. The new stars are significantly
fainter at maximum light than the three previously known LMC RCB stars. The
amount of reddening toward these stars is somewhat uncertain but both seem to
have absolute magnitudes, M_V, about half a magnitude fainter than the other
three stars. Estimates of M_Bol find that the 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 number of known RCB stars in the LMC and demonstrates the utility of
the MACHO photometric database for the discovery of new RCB stars.
We report the discovery of eight new R Coronae Borealis (RCB) stars in the Large Magellanic Cloud (LMC) using the MACHO project photometry database. The 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 Galactic variable DY Per. These stars decline much more slowly and are cooler than the RCB stars. The absolute luminosities of the Galactic RCB stars are unknown since there is no direct measurement of the distance to any Galactic RCB star. Hence, the importance of the LMC RCB stars. We find a much larger range of absolute magnitudes (M(V) = -2.5 to -5 mag) than inferred from the small pre-MACHO sample of LMC RCB stars. It is likely that there is a temperature - M(V)relationship with the cooler stars being intrinsically fainter. Cool (~5000 K) RCB stars are much more common than previously thought based on the Galactic RCB star sample. Using the fairly complete sample of RCB stars discovered in the MACHO fields, we have estimated the likely number of RCB stars in the Galaxy to be ~3,200. The SMC MACHO fields were also searched for RCB stars but none were found.
We report the discovery of two new R Coronae Borealis (RCB) stars in the Large Magellanic Cloud (LMC) using the MACHO project photometry database. The identification of both stars has been confirmed ...spectroscopically. One is a cool RCB star (T_eff about 5000 K) characterized by very strong Swan bands of C_2 and violet bands of CN, and weak or absent Balmer lines, G-band and 12C-13C bands. The second star is an example of a hot RCB star of which only 3 were previously known to exist in the Galaxy 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 > 4 mag in brightness. The new stars are significantly fainter at maximum light than the three previously known LMC RCB stars. The amount of reddening toward these stars is somewhat uncertain but both seem to have absolute magnitudes, M_V, about half a magnitude fainter than the other three stars. Estimates of M_Bol find that the 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 number of known RCB stars in the LMC and demonstrates the utility of the MACHO photometric database for the discovery of new RCB stars.
