  We study ensembles of 1/2-BPS bound states of fundamental strings and
NS-fivebranes (NS5-F1 states) in the AdS decoupling limit. We revisit a
solution corresponding to an ensemble average of these bound states, and find
that the appropriate duality frame for describing the near-source structure is
the T-dual NS5-P frame, where the bound state is a collection of momentum waves
on the fivebranes. We find that the fivebranes are generically well-separated;
this property results in the applicability of perturbative string theory. The
geometry sourced by the typical microstate is not close to that of an extremal
non-rotating black hole; instead the fivebranes occupy a ball whose radius is
parametrically much larger than the "stretched horizon" scale of the
corresponding black hole. These microstates are thus better characterized as
BPS fivebrane stars than as small black holes.
  When members of the ensemble spin with two fixed angular potentials about two
orthogonal planes, we find that the spherical ball of the non-rotating ensemble
average geometry deforms into an ellipsoid. This contrasts with ring structures
obtained when fixing the angular momenta instead of the angular potentials; we
trace this difference of ensembles to large fluctuations of the angular
momentum in the ensemble of fixed angular potential.
