  In this work, we present new data on the $^{89}$Y($\gamma$,n) cross section
studied with a quasi-monochromatic photon beam produced at the NewSUBARU
synchrotron radiation facility in Japan contributing torwards resolving a long
standing discrepancy between existing measurements of this cross section.
Results for $\gamma$-ray strength function below threshold obtained by applying
the Oslo method to $^{89}$Y($p,p'\gamma$)$^{89}$Y coincidences combined with
the $^{89}$Y($\gamma$,n) data this providing experimental data for the
$\gamma$-ray strength function of $^{89}$Y for $\gamma$ energies in the range
of $\approx 1.6$ Mev to $\approx$ 20 MeV. A low-energy enhancement is seen for
$\gamma$-rays below $\approx 2.5$ MeV. Shell-model calculations indicate that
this feature is caused by strong, low-energy $M1$ transitions at high
excitation energies. The nuclear level density and $\gamma$-ray strength
function have been extracted from $^{89}$Y($d,p \gamma$)$^{90}$Y coincidences
using the Oslo method. Using the ($\gamma,n$) and ($d,p\gamma$) data as
experimental constraints, we have calculated the $^{89}$Y($n,\gamma$)$^{90}$Y
cross section with the TALYS reaction code. Our results have been compared with
directly measured (n,$\gamma$) cross sections and evaluations. The $N=50$
isotope $^{89}$Y is an important bottleneck in the s-process and the magnitude
of the $^{89}$Y(n,$\gamma)$ cross section is key to understanding how s-process
stars produce heavy isotopes.
