New bulk cone singularities in Vaidya-like spacetimes from large $c$ conformal blocks

Bulk cone singularities are singularities in boundary two-point functions at points separated by a null geodesic in the bulk, but not in the boundary. In this work, we describe a new type of bulk cone singularities in a family of Vaidya-like spacetimes that are labeled by the radius $r_{+}$ of the resulting black hole. We find a sharp transition in the causal structure within this family of spacetimes at $r_{+}=l$, the AdS length. In particular, there are bulk cone singularities that do not exist in the $r_{+}>l$ case, but appear for $r_{+}<l$. In the case of $r_{+}<l$ where such singularities exist, we are able to reproduce the singularities in a CFT${}_2$ calculation using large $c$ conformal blocks.