Revised surface abundances of R Coronae Borealis stars
arXiv:2108.02736 · doi:10.3847/1538-4357/ac1ad1
Abstract
Surface abundances of 14 (11 majority class and 3 minority class) R Coronae Borealis stars (RCBs) along with the final flash object, V4334 Sgr (Sakurai's object) are revised based on their carbon abundances measured from the observed C2 bands; note that the earlier reported abundances were derived using an assumed carbon abundance due to the well known ``carbon problem''. The hot RCB MV Sgr is not subject to a carbon problem; it is remarkable to note that MV Sgr's carbon abundance lies in the range that is measured for the majority and minority class RCBs. The revised iron abundances for the RCBs are in the range log E(Fe)=3.8 to log E(Fe)=5.8 with the minority class RCB V854 Cen at lower end and the majority class RCB R CrB at the higher end of this range. Indications are that the revised RCBs' metallicity range is roughly consistent with the metal poor population contained within the bulge. The revised abundances of RCBs are then compared with extreme helium stars (EHes), the hotter relatives of RCBs. Clear differences are observed between RCBs and EHes in their metallicity distribution, carbon abundances, and the abundance trends observed for the key elements. These abundances are further discussed in the light of their formation scenarios.
Accepted for publication in the Astrophysical Journal (ApJ), 31 pages, 14 figures,
References in corpus (13)
- Gaia Data Release 1. Summary of the astrometric, photometric, and survey properties
- The orbits of open clusters in the Galaxy
- Post-merger evolution of carbon-oxygen + helium white dwarf binaries and the origin of R Coronae Borealis and extreme helium stars
- The evolution of the Milky Way: New insights from open clusters
- Fluorine in R Coronae Borealis Stars
- GALEX J184559.8-413827: a new extreme helium star identified using SALT
- Census of R Coronae Borealis stars I: Infrared light curves from Palomar Gattini IR
- R Coronae Borealis Star Evolution: Simulating 3D Merger Events to 1D Stellar Evolution Including Large Scale Nucleosynthesis
- Abundance analysis of cool extreme helium star: LSS 3378
- Non-Local Thermodynamic Equilibrium abundance analyses of the extreme helium stars: V652 Her and HD 144941
- SALT revisits DY Cen: a rapidly-evolving strontium-rich single helium star
- Abundance analyses of the new R Coronae Borealis stars: ASAS-RCB-8 and ASAS-RCB-10
- On the binary helium star DY Centauri: Chemical composition and evolutionary state