D1D5 systems and AdS/CFT correspondences with 16 supercharges
  We study the spectra of BPS excitations of D1D5 bound states in a class of free orbifolds/orientifolds of type IIB theory and its dual descriptions in terms of chiral primaries of the corresponding $AdS_3$ supergravities. 
Edi Gava, Amine B. Hammou, Jose F. Morales and Kumar S. Narain