BPS defects in AdS₃ supergravity

AdS supergravity admits supersymmetric solutions that describe BPS defects. Here, we investigate such solutions in AdS$_3$ supergravity, which is formulated as a Chern-Simons theory on $\mathrm{OSp}(2|1)\,\times\, \mathrm{OSp}(2|1)$. We compute the Killing spinor equation on the BTZ geometry in different ways, looking for BPS solutions on the entire space of parameters. We focus our attention on defects that represent geometries with integer angular excesses; these correspond to specific negative values of the BTZ mass. We compare our solutions with other results in the literature, finding exact agreement. We argue that, in the semiclassical limit, the BPS defects can be associated to degenerate representations of the Virasoro symmetry at the boundary. The case of non-diagonal representations, describing stationary, non-static defects, is also discussed.