  We report new STAR measurements of the single-spin asymmetries $A_L$ for
$W^+$ and $W^-$ bosons produced in polarized proton--proton collisions at
$\sqrt{s}$ = 510 GeV as a function of the decay-positron and decay-electron
pseudorapidity. The data were obtained in 2013 and correspond to an integrated
luminosity of 250 pb$^{-1}$. The results are combined with previous results
obtained with 86 pb$^{-1}$. A comparison with theoretical expectations based on
polarized lepton-nucleon deep-inelastic scattering and prior polarized
proton--proton data suggests a difference between the $\bar{u}$ and $\bar{d}$
quark helicity distributions for $0.05 < x < 0.25$. In addition, we report new
results for the double-spin asymmetries $A_{LL}$ for $W^\pm$, as well as $A_L$
for $Z/\gamma^*$ production and subsequent decay into electron--positron pairs.
