Three new barium dwarfs with white dwarf companions: BD+68°1027, RE J0702+129 and BD+80°670
Abstract
We report three new barium (Ba) dwarfs lying in Sirius-like systems. They provide direct evidence that Ba dwarfs are companions to white dwarfs (WDs). Atmospheric parameters, stellar masses and the chemical abundances of 25 elements, including light, α, Fe-peak and s-process elements, are derived from high-resolution and high S/N spectra. The enhancement of s-process elements with [s/Fe] ratios between 0.4 and 0.6 confirm them as mild barium stars. The estimated metallicities (-0.31, -0.06 and 0.13) of BD+68°1027, RE J0702+129 and BD+80°670 are in the range of known Ba dwarfs and giants. As expected, the observed indices [hs/ls], [s/Fe] and [C/Fe] show an anti-correlation with metallicity. Asymptotic giant branch (AGB) progenitor masses are estimated for the WD companions of RE J0702+129 (1.47 M⊙) and BD+80°670 (3.59 M⊙). These confirm the predicted range of progenitor AGB masses (1.5-4 M⊙) for unseen WDs around Ba dwarfs. The surface abundances of s-process elements in RE J0702+129 and BD+80°670 are compared with AGB models and they are in close agreement, within the predicted accretion efficiencies and pollution factors for Ba stars. These results support that the origin of s-process overabundances in Ba dwarfs is similar to those of Ba giants via the McClure hypothesis in which Ba stars accumulate s-process elements through mass transfer from their host companions during the AGB phase.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- February 2018
- DOI:
- 10.1093/mnras/stx2809
- arXiv:
- arXiv:1710.10750
- Bibcode:
- 2018MNRAS.474.2129K
- Keywords:
-
- stars: abundances;
- binaries: general;
- stars: chemically peculiar;
- stars: fundamental parameters;
- white dwarfs;
- Astrophysics - Solar and Stellar Astrophysics
- E-Print:
- 12 pages, 8 figures, 8 tables