  Mass loss of massive helium stars is not well understood even though it plays
an essential role in determining their remnant neutron-star or black-hole
masses as well as ejecta mass of Type Ibc supernovae. Radio emission from Type
Ibc supernovae is strongly affected by circumstellar matter properties formed
by mass loss of their massive helium star progenitors. In this study, we
estimate the rise time and peak luminosity distributions of Type Ibc supernovae
in radio based on a few massive helium star mass-loss prescriptions and compare
them with the observed distribution to constrain the uncertain massive helium
star mass-loss rates. We find that massive helium stars in the luminosity range
expected for ordinary Type Ibc supernova progenitors (4.6 ~< log L/Lsun ~< 5.2)
should generally have large mass-loss rates (> ~ 1e-6 Msun/yr) in order to
account for the observed rise time and peak luminosity distribution. Therefore,
mass-loss prescriptions that predict significantly low mass-loss rates for
helium stars in this luminosity range is inconsistent with the supernova radio
observations. It is also possible that massive helium stars shortly before
their explosion generally undergo mass-loss enhancement in a different way from
the standard radiation-driven wind mechanism.
