There is now strong evidence that some stars have been born with He mass fractions as high as Y \approx 0.40 ( e.g. , in \omega Centauri ) .
However , the advanced evolution , chemical yields , and final fates of He-rich stars are largely unexplored .
We investigate the consequences of He-enhancement on the evolution and nucleosynthesis of intermediate-mass asymptotic giant branch ( AGB ) models of 3 , 4 , 5 , and 6 \mathrm { M } _ { \sun } with a metallicity of Z = 0.0006 ( [ Fe/H ] \approx - 1.4 ) .
We compare models with He-enhanced compositions ( Y = 0.30 , 0.35 , 0.40 ) to those with primordial He ( Y = 0.24 ) .
We find that the minimum initial mass for C burning and super-AGB stars with CO ( Ne ) or ONe cores decreases from above our highest mass of 6 \mathrm { M } _ { \sun } to \sim 4 – 5 \mathrm { M } _ { \sun } with Y = 0.40 .
We also model the production of trans-Fe elements via the slow neutron-capture process ( s -process ) .
He-enhancement substantially reduces the third dredge-up efficiency and the stellar yields of s -process elements ( e.g. , 90 % less Ba for 6 \mathrm { M } _ { \sun } , Y = 0.40 ) .
An exception occurs for 3 \mathrm { M } _ { \sun } , where the near-doubling in the number of thermal pulses with Y = 0.40 leads to \sim 50 \% higher yields of Ba-peak elements and Pb if the ^ { 13 } { \text { C } } neutron source is included .
However , the thinner intershell and increased temperatures at the base of the convective envelope with Y = 0.40 probably inhibit the ^ { 13 } { \text { C } } neutron source at this mass .
Future chemical evolution models with our yields might explain the evolution of s -process elements among He-rich stars in \omega Centauri .