  Observations suggest that some massive stars experience violent and eruptive
mass loss associated with significant brightening that cannot be explained by
hydrostatic stellar models. This event seemingly forms dense circumstellar
matter (CSM). The mechanism of eruptive mass loss has not been fully explained.
We focus on the fact that the timescale of nuclear burning gets shorter than
the dynamical timescale of the envelope a few years before core collapse for
some massive stars. To reveal the properties of the eruptive mass loss, we
investigate its relation to the energy injection at the bottom of the envelope
supplied by nuclear burning taking place inside the core. In this study, we do
not specify the actual mechanism for transporting energy from the site of
nuclear burning to the bottom of the envelope. Instead, we parameterize the
amount of injected energy and the injection time and try to extract information
on these parameters from comparisons with observations. We carried out 1-D
radiation hydrodynamical simulations for progenitors of red, yellow, and blue
supergiants, and Wolf-Rayet stars. We calculated the evolution of the
progenitors with a public stellar evolution code. We obtain the light curve
associated with the eruption, the amount of ejected mass, and the CSM
distribution at the time of core-collapse. The energy injection at the bottom
of the envelope of a massive star within a period shorter than the dynamical
timescale of the envelope could reproduce some observed optical outbursts prior
to the core-collapse and form the CSM, which can power an interaction supernova
(SN) classified as type IIn.
