How Many R Coronae Borealis Stars Are There Really?

摘要

The R Coronae Borealis (RCB) stars are rare hydrogen-deficient, carbon-rich supergiants. Two evolutionary scenarios have been suggested, a double degenerate merger of two white dwrfs (WDs), or a final helium shell flash in a planetary nebula central star. Only about 100 of the predicted 3,000 RCB stars in the Galaxy have been discovered. But the pace of discovery of new RCB stars in the Milky Way has been accelerating. We recently discovered over twenty new RCB stars by examining ASAS-e light curves. Using the recent release of the WISE All-Sky Catalog, a series of IR color-color cuts have produced a sample of candidates that may yield over 200 new RCB stars. We are trying to obtain spectra of these stars to confirm their identifications. The evidence pointing toward a WD merger or a final-flash origin for RCB stars is contradictory. Increasing the sample of known RCB stars, so that we can better study their spatial distribution in the Galaxy, can give us clues to their origins. Their number and distribution may be consistent with WD mergers. If so, this would be an exciting result since RCB stars may be low-mass analogs of Type la supernovae.