Let $\Sigma$ be a compact connected oriented 2-manifold of genus $g\geq 2$, and let $p$ be a point on $\Sigma$. We define a space $S_g(t)$ consisting of certain irreducible representations of the fundamental group of $\Sigma \setminus p$, modulo conjugation by a compact Lie group $G$.
When $G=SU(2)$, Weitsman considered a tautological line bundle on $S_g(t)$, and proved that the $2g$^{th} power of its first Chern class vanishes, as conjectured by Newstead. In this talk I will describe my extension of his work to $G=SO(2n+1)$.