R Coronae Borealis variables


 * R Coronae Borealis variables
 * A R Coronae Borealis variable (abbreviated RCB) is an eruptive variable star that varies in luminosity in two modes, one low amplitude pulsation (a few tenths of a magnitude), and one irregular unpredictably sudden fading by 1 to 9 magnitudes.


 * Wikipedia
 * AAVSO Description
 * Discovery of Bright Galactic R Coronae Borealis and DY Persei Variables: Rare Gems Mined from ACVS