Tau Functions of (n,1) curves and Soliton Solutions on Non-Zero Constant Backgrounds

We study the tau function of the KP-hierarchy associated with an (n,1) curve $y^n=x-\alpha$. If $\alpha =0$ the corresponding tau function is 1. On the other hand if $\alpha \mathrm{\ne }0$ the tau function becomes the exponential of a quadratic function of the time variables. By applying vertex opertaors to the latter we obtain soliton solutions on non-zero constant backgrounds.