  Broad-lined type Ic supernovae (SNe Ic-BL) are of great importance because
their association with long-duration gamma-ray bursts (LGRBs) holds the key to
deciphering the central engine of LGRBs, which refrains from being unveiled
despite decades of investigation. Among the two popularly hypothesized types of
central engine, i.e., black holes and strongly magnetized neutron stars
(magnetars), there is mounting evidence that the central engine of
GRB-associated SNe (GRB-SNe) is rapidly rotating magnetars. Theoretical
analysis also suggests that magnetars could be the central engine of SNe Ic-BL.
What puzzled the researchers is the fact that light curve modeling indicates
that as much as 0.2-0.5 solar mass of 56Ni was synthesized during the explosion
of the SNe Ic-BL, which is unfortunately in direct conflict with current
state-of-the-art understanding of magnetar-powered 56Ni synthesis. Here we
propose a dynamic model of magnetar-powered SNe to take into account the
acceleration of the ejecta by the magnetar, as well as the thermalization of
the injected energy. Assuming that the SN kinetic energy comes exclusively from
the magnetar acceleration, we find that although a major fraction of the
rotational energy of the magnetar is to accelerate the SNe ejecta, a tiny
fraction of this energy deposited as thermal energy of the ejecta is enough to
reduce the needed 56Ni to 0.06 solar mass for both SN 1997ef and SN 2007ru. We
therefore suggest that magnetars could power SNe Ic-BL both in aspects of
energetics and of 56Ni synthesis.
