R Coronae Borealis [SEP] constellation
R Coronae Borealis
R Coronae Borealis is a peculiar low-mass yellow supergiant star in the constellation of Corona Borealis. It is the prototype of the rare RCB class of variable stars, which fade by several magnitudes at irregular intervals. R Coronae Borealis itself normally shines at approximately magnitude 6, just about visible to the naked eye, but at intervals of several months to many years fades to as faint as 15th magnitude. Over successive months it then gradually returns to its normal brightness, giving it the nickname "reverse nova
V Coronae Australis
V Coronae Australis (V CrA) is a R Coronae Borealis variable star in the constellation Corona Australis. These are extremely hydrogen-deficient supergiants thought to have arisen as the result of the merger of two white dwarfs; fewer than 100 have been discovered as of 2012. V Coronae Australis dimmed in brightness from 1994 to 1998.
It has around 60% the mass of the Sun and an effective (surface) temperature of around 6250 K.