The slow ( s ) and intermediate ( i ) neutron ( n ) capture processes occur both in asymptotic giant branch ( AGB ) stars , and in massive stars .
To study the build-up of the s - and i -products at low metallicity , we investigate the abundances of Y , Ba , La , Nd , and Eu in 98 stars , at -2.4 < \text { [ Fe / H ] } < -0.9 , in the Sculptor dwarf spheroidal galaxy .
The chemical enrichment from AGB stars becomes apparent at \text { [ Fe / H ] } \approx - 2 in Sculptor , and causes [ Y/Ba ] , [ La/Ba ] , [ Nd/Ba ] and [ Eu/Ba ] to decrease with metallicity , reaching subsolar values at the highest \text { [ Fe / H ] } \approx - 1 .
To investigate individual nucleosynthetic sites , we compared three n -rich Sculptor stars with theoretical yields .
One carbon-enhanced metal-poor ( CEMP-no ) star with high \text { [ Sr,Y,Zr ] } > +0.7 is best fit with a model of a rapidly-rotating massive star , the second ( likely CH star ) with the i -process , while the third has no satisfactory fit .
For a more general understanding of the build-up of the heavy elements , we calculate for the first time the cumulative contribution of the s - and i -processes to the chemical enrichment in Sculptor , and compare with theoretical predictions .
By correcting for the r -process , we derive \text { [ Y / Ba ] } _ { s / i } = -0.85 \pm 0.16 , \text { [ La / Ba ] } _ { s / i } = -0.49 \pm 0.17 , and \text { [ Nd / Ba ] } _ { s / i } = -0.48 \pm 0.12 , in the overall s - and/or i -process in Sculptor .
These abundance ratios are within the range of those of CEMP stars in the Milky Way , which have either s - or i -process signatures .
The low \text { [ Y / Ba ] } _ { s / i } and \text { [ La / Ba ] } _ { s / i } that we measure in Sculptor are inconsistent with them arising from the s -process only , but are more compatible with models of the i -process .
Thus we conclude that both the s - and i -processes were important for the build-up of n -capture elements in the Sculptor dwarf spheroidal galaxy .