We determined chemical abundances of the Extremely Metal-Poor ( EMP ) star S 15–19 ( [ Fe/H ] = -3.0 ) in the Sextans dwarf galaxy .
While heavy neutron-capture elements ( e.g. , Ba ) are generally deficient in EMP stars in dwarf galaxies , this object was shown to have an exceptional over-abundance of Ba ( [ Ba/Fe ] \sim + 0.5 ) by a previous study , which is similar to those of r-process-enhanced stars found in the field halo .
Our new high-resolution spectroscopy for this object for the blue region , however , reveals that no clear excess of r-process elements , like Eu , appears in this object .
Moreover , a significant excess of carbon ( [ C/Fe ] = +1.0 ) and a deficiency of Sr ( [ Sr/Fe ] = -1.4 ) are found for this object .
Taking the variation of radial velocities measured at the two different epochs into consideration , the origin of the excesses of heavy neutron-capture elements in S 15–19 is not the r-process , but is the s-process in an asymptotic giant branch ( AGB ) star that was the binary companion ( primary ) of this object .
Carbon- and s-process-enhanced material should have been transferred to the surface of S 15–19 across the binary system .
These results are compared with carbon-enhanced metal-poor stars in the field halo .