V Coronae Australis Explained

V Coronae Australis (V CrA) is a R Coronae Borealis variable (RCB) 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.^[1] V Coronae Australis dimmed in brightness from 1994 to 1998.^[2]

The visual apparent magnitude of V CrA has been observed to vary between magnitudes 9.4 and 17.9. A maximum magnitude of 8.3 has been estimated from photographic plates.^[3] It has around 60% the mass of the Sun and an effective (surface) temperature of around 6250 K.^[4]

The spectral class of R0 is typical of a carbon star, but the RCB stars are considered to a separate class of hydrogen-deficient stars, not normal asymptotic giant branch giants.^[5]

Notes and References

1. Tisserand. Clayton. Welch. Pilecki. Wyrzykowski. Kilkenny. The Ongoing Pursuit of R Coronae Borealis Stars: ASAS-3 Survey Strikes Again . 2012 . 2013A&A...551A..77T . Astronomy & Astrophysics . 551 . A77 . 22. 1211.2475 . 10.1051/0004-6361/201220713 . 59060842.
2. Skuljan, L. . Cottrell, P. L. . 2002. Recent declines of RS Telescopii, UW Centauri, and V Coronae Australis. The Observatory. 122. 322–29. 2002Obs...122..322S.
3. 1975IBVS..989....1M . A Note on V CrA and W Men . Milone . L. A. . Information Bulletin on Variable Stars . 1975 . 989 . 1 .
4. 2006A&A...450..701S. Post-AGB stars as testbeds of nucleosynthesis in AGB stars. Astronomy and Astrophysics. 450. 2. 701. Stasińska. G.. Szczerba. R.. Schmidt. M.. Siódmiak. N.. 2006. 10.1051/0004-6361:20053553. astro-ph/0601504 . 12040452.
5. 2021ApJ...921...52P . Revised Surface Abundances of R Coronae Borealis Stars . Pandey . Gajendra . Hema . B. P. . Reddy . Arumalla B. S. . The Astrophysical Journal . 2021 . 921 . 1 . 52 . 10.3847/1538-4357/ac1ad1 . 2108.02736 . 236924306 . free .