Mon. Not. R. Astron. Soc., 474, 2129-2141 (2018/February-3)
Three new barium dwarfs with white dwarf companions: BD+68°1027, RE J0702+129 and BD+80°670.
KONG X.M., BHARAT KUMAR Y., ZHAO G., ZHAO J.K., FANG X.S., SHI J.R., WANG L., ZHANG J.B. and YAN H.L.
Abstract (from CDS):
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.
© 2017 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society
stars: abundances - binaries: general - stars: chemically peculiar - stars: fundamental parameters - white dwarfs
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