  The nature of an emerging class of rapidly fading supernovae
(RFSNe)--characterized by their short-lived light curve duration, but varying
widely in peak brightness--remains puzzling. Whether the RFSNe arise from
low-mass thermonuclear eruptions on white dwarfs or from the core collapse of
massive stars is still a matter of dispute. We explore the possibility that the
explosion of hydrogen-free massive stars could produce bright but rapidly
fading transients if the effective pre-supernova radii are large and if little
or no radioactive nickel is ejected. The source of radiation is then purely due
to shock cooling. We study this model of RFSNe using spherically symmetric
hydrodynamics and radiation transport calculations of the explosion of stripped
stars embedded in helium-dominated winds or shells of various masses and
extent. We present a parameter study showing how the properties of the
circumstellar envelopes affect the dynamics of the explosion and can lead to a
diversity of light curves. We also explore the dynamics of the fallback of the
innermost stellar layers, which might be able to remove radioactive nickel from
the ejecta, making the rapid decline in the late time light curve possible. We
provide scaling relations that describe how the duration and luminosity of
these events depend on the supernova kinetic energy and the mass and radius of
the circumstellar material.

High Energy Astrophysical Phenomena