  Janis-Newman-Winicour (JNW) spacetimes generalize the Schwarzschild solution
to include a massless scalar field. Although suffering from naked
singularities, they share the `frozen star' features of Schwarzschild black
holes. Cosmological versions of the JNW spacetimes were discovered some time
ago by Husain, Martinez and Nunez and by Fonarev. Unlike Schwarzschild-deSitter
black holes, these solutions are dynamical, and the scarcity of exact solutions
for dynamical black holes in cosmological backgrounds motivates their further
study. Here we show how the cosmological JNW spacetimes can be built, starting
from simpler, static, higher dimensional, vacuum `JNW brane' solutions via two
different generalized dimensional reduction schemes that together cover the
full range of JNW parameter space. Cosmological versions of a BPS limit of
charged dilaton black holes are also known. JNW spacetimes represent a
different limiting case of the charged, dilaton black hole family. We expect
that understanding this second data point may be key to finding cosmological
versions of general, non-BPS black holes.
