$N=4$ supersymmetric ${\mathrm{BMS}}_3$ algebras from asymptotic symmetry analysis

We consider three dimensional $N=4$ flat supergravity, with an Abelian R-symmetry enhancing the gravitational phase space. We obtain the field configuration whose asymptotic symmetries at null infinity coincide with the centrally extended $N=4$ super-Bondi-Metzner-Sachs (BMS) algebra. The killing spinors for this generic configuration are obtained together with the energy bounds imposed by supersymmetry. It is explicitly shown that the same algebra can be obtained as a flat (AdS radius $\to \infty$) limit of the combined (2,0) and (0,2) sectors of AdS supergravity.