Abundance analyses of helium-rich subluminous B stars

Abstract

The connection between helium-rich hot subdwarfs of spectral types O and B (He-sdB) has been relatively unexplored since the latter were found in significant numbers in the 1980's. In order to explore this connection further, we have analysed the surface composition of six He-sdB stars, including LB 1766, LB 3229, SB 21 (= Ton-S 137 = BPS 29503-0009), BPS 22940-0009, BPS 29496-0010, and BPS 22956-0094. Opacity-sampled line-blanketed model atmospheres have been used to derive atmospheric properties and elemental abundances. All the stars are moderately metal-poor compared with the Sun ([Fe/H] ~ -0.5). Four stars are nitrogen-rich, two of these are carbon-rich, and at least four appear to be neon-rich. The data are insufficient to rule out binarity in any of the sample. The surface composition and locus of the N-rich He-sdBs are currently best explained by the merger of two helium white dwarfs, or possibly by the merger of a helium white dwarf with a post-sdB white dwarf. C-rich He-sdBs require further investigation.

Accepted 2010 July 7

References in corpus (3)

• Hot subdwarfs from the ESO Supernova Ia Progenitor Survey: II. Atmospheric parameters of subdwarf O stars
• Modeling He-rich subdwarfs through the hot-flasher Scenario
• Mass-loss and diffusion in subdwarf B stars and hot white dwarfs: do weak winds exist?

Cited by in corpus (20)

• The fastest unbound star in our Galaxy ejected by a thermonuclear supernova
• The population of hot subdwarf stars studied with Gaia -- IV. Catalogues of hot subluminous stars based on Gaia EDR3
• The catalogue of radial velocity variable hot subluminous stars from the MUCHFUSS project
• Discovery of extremely lead-rich subdwarfs: does heavy metal signal the formation of subdwarf B stars?
• On helium-dominated stellar evolution: the mysterious role of the O(He)-type stars
• Discovery of a variable lead-rich hot subdwarf: UVO 0825+15
• Evolution models of helium white dwarf--main sequence star merger remnants
• Stellar wind models of subluminous hot stars
• The SALT survey of helium-rich hot subdwarfs: methods, classification, and coarse analysis
• GALEX J184559.8-413827: a new extreme helium star identified using SALT
• A search for heavy-metal stars: abundance analyses of hot subdwarfs with Subaru
• Spectroscopic Orbital Elements for the Helium-Rich Subdwarf Binary PG1544+488
• PHL 417: a zirconium-rich pulsating hot subdwarf (V366 Aquarid) discovered in K2 data
• Post-merger evolution of double helium white dwarfs and distribution of helium-rich hot subdwarfs
• Asteroseismic signatures of the helium-core flash
• EVR-CB-004: An Inflated Hot Subdwarf O star + Unseen WD Companion in a Compact Binary Discovered with the Evryscope
• Spectroscopic analysis of BPS CS 22940-0009: connecting evolved helium stars
• Observational Parameters of Blue Large-amplitude Pulsators
• NLTE spectral analysis of the intermediate helium-rich subdwarf B star CPD-20°1123
• Abundance analysis of a nitrogen-rich extreme-helium hot subdwarf from the SALT survey