Picard Groups of Stacky Curves

Abstract: We describe the Picard group of a tame stacky curve as an extension of two groups, which depend on the gerbe class of the curve over its rigidification, a stacky curve with trivial generic stabilizer, and the residual gerbes of the rigidification. After presenting the general formulation, we compute some specific examples. In particular, we provide an example highlighting the fact that the extension of the groups truly depends on the class of the gerbe.