2011/04/26 by Drew Clausen, R. A. Wade, Richard A. Wade
Physics and Astronomy · #Astronomy #Astronomy and Astrophysical Research #Astrophysics #Common envelope #Gamma-ray bursts and supernovae #Globular cluster #Horizontal branch #Merge (version control) #Physics #Roche lobe #Singleton #Star formation #Stars #Stellar, planetary, and galactic studies #Subdwarf #White dwarf #astro-ph.SR
paper · pdf · doi:10.1088/2041-8205/733/2/l42
5 pages, 3 figures, accepted for publication ApJL
arxiv created 2011/04/26 · openalex publication_date 2011/05/11 · arxiv updated 2015/05/28 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
Many hot subdwarf B stars (sdBs) are in close binaries, and the favored formation channels for subdwarfs rely on mass transfer in a binary system to strip a core He-burning star of its envelope. However, these channels cannot account for sdBs that have been observed in long-period binaries nor the narrow mass distribution of isolated (or "singleton") sdBs. We propose a new formation channel involving the merger of a helium white dwarf and a low-mass, hydrogen-burning star, which addresses these issues. Hierarchical triples whose inner binaries merge and form sdBs by this process could explain the observed long-period subdwarf+main-sequence binaries. This process would also naturally explain the observed slow rotational speeds of singleton sdBs. We also briefly discuss the implications of this formation channel for extreme horizontal branch morphology in globular clusters and the UV upturn in elliptical galaxies.