We report three new barium ( Ba ) dwarfs lying in Sirius-like systems , which provides direct evidence that Ba dwarfs are companions to white dwarfs ( WDs ) .
Atmospheric parameters , stellar masses , and chemical abundances of 25 elements , including light , \alpha , Fe-peak and s-process elements , are derived from high resolution and high S/N spectra .
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 , 0.13 ) of BD+68 ^ { \circ } 1027 , RE J0702+129 and BD+80 ^ { \circ } 670 are in the range of known Ba dwarfs and giants .
As expected , observed indices of [ hs/ls ] , [ s/Fe ] and [ C/Fe ] show anticorrelation with metallicity .
AGB progenitor masses are estimated for the WD companions of RE J0702+129 ( 1.47 M _ { \odot } ) and BD+80 ^ { \circ } 670 ( 3.59 M _ { \odot } ) , which confirms the predicted range of progenitor AGB masses ( 1.5 \sim 4 M _ { \odot } ) for unseen WDs around Ba dwarfs .
Surface abundances of s-process elements in RE J0702+129 and BD+80 ^ { \circ } 670 are compared with AGB models and they are in close agreement , within 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 Ba giants via McClure hypothesis in which Ba stars accumulate s-process elements through mass transfer from their host companions during AGB phase .