We present updated calculations of stellar evolutionary sequences and detailed nucleosynthesis predictions for the brightest asymptotic giant branch ( AGB ) stars in the Galaxy with masses between 5 { M } _ { \sun } to 9 { M } _ { \sun } , with an initial metallicity of Z = 0.02 ( [ Fe/H ] = 0.14 ) .
In our previous studies we used the Vassiliadis & Wood ( 66 ) mass-loss rate , which stays low until the pulsation period reaches 500 days after which point a superwind begins . Vassiliadis & Wood ( 66 ) noted that for stars over 2.5 { M } _ { \sun } the superwind should be delayed until P \approx 750 days at 5 { M } _ { \sun } .
We calculate evolutionary sequences where we delay the onset of the superwind to pulsation periods of P \approx 700 - 800 days in models of M = 5 , 6 , and 7 { M } _ { \sun } .
Post-processing nucleosynthesis calculations show that the 6 and 7 { M } _ { \sun } models produce the most Rb , with [ Rb/Fe ] \approx 1 Â dex , close to the average of most of the Galactic Rb-rich stars ( [ Rb/Fe ] \approx 1.4 \pm 0.8 Â dex ) .
Changing the rate of the ^ { 22 } { N } e + \alpha reactions results in variations of [ Rb/Fe ] as large as 0.5Â dex in models with a delayed superwind .
The largest enrichment in heavy elements is found for models that adopt the NACRE rate of the ^ { 22 } { N } e ( \alpha , n ) ^ { 25 } { M } g reaction .
Using this rate allows us to best match the composition of most of the Rb-rich stars .
A synthetic evolution algorithm is then used to remove the remaining envelope resulting in final [ Rb/Fe ] of \approx 1.4 Â dex although with C/O ratios > 1 .
We conclude that delaying the superwind may account for the large Rb overabundances observed in the brightest metal-rich AGB stars .