We work with a smooth relative curve $X_U/U$ with nodal reduction over an excellent and locally factorial scheme $S$. We show that blowing up a nodal model of $X_U$ in the ideal sheaf of a section yields a new nodal model, and describe how these models relate to each other. We construct a Néron model for the Jacobian of $X_U$, and describe it locally on $S$ as a quotient of the Picard space of a well-chosen nodal model. We provide a combinatorial criterion for the Néron model to be separated.

Comment: 37 pages including bibliography. Comments are welcome. To appear in \'Epijournal de Géométrie Algébrique, Volume 6 (2022), Article No. 17

• 14H10 - Families, moduli of curves (algebraic)
• 14H40 - Jacobians, Prym varieties