Moduli spaces of SL(r)-bundles on singular irreducible curves

For a stable irreducible curve $X$ and a torsion free sheaf $L$ on $X$ of rank one and degree $d$, D.S. Nagaraj and C.S. Seshadri ([NS]) defined a closed subset $\text{Cal}{U}_X(r,L)$ in the moduli space of semistable torsion free sheaves of rank $r$ and degree $d$ on $X$. We prove that $\text{Cal}{U}_X(r,L)$ is irreducible, when a smooth curve $Y$ specializes to $X$ and a line bundle $\Cal L$on$Y$specializesto$L$, the specialization of moduli space of semistable rank $r$ vector bundles on $Y$ with fixed determinant $\text{Cal}L$ has underlying set $\text{Cal}{U}_X(r,L)$. For rank 2 and 3, we show that there is a Cohen-Macaulay closed subscheme in the Gieseker space which represents a suitable moduli functor and has good specialization property.