  We perform a series of two-dimensional, axisymmetric, magnetohydrodynamic
simulations of the rotational collapse of a supernova core. In order to
calculate the waveforms of the gravitational wave, we derive the quadrupole
formula including the contributions from the electromagnetic fields. Recent
stellar evolution calculations imply that the magnetic fields of the toroidal
components are much stronger than those of the poloidal ones at the
presupernova stage. Thus, we systematically investigate the effects of the
toroidal magnetic fields on the amplitudes and waveforms. Furthermore, we
employ the two kinds of the realistic equation of states, which are often used
in the supernova simulations. Then, we investigate the effects of the equation
of states on the gravitational wave signals. With these computations, we find
that the peak amplitudes are lowered by an order of 10% for the models with the
strongest toroidal magnetic fields. However, the peak amplitudes are mostly
within sensitivity range of laser interferometers such as TAMA and the first
LIGO for a source at a distance of 10 kpc. Furthermore, we point out that the
amplitudes of second peaks are still within the detection limit of the first
LIGO for the source, although the characteristics of second peaks are reduced
by the magnetic fields. We stress the importance of the detection, since it
will give us information about the angular momentum distribution of massive
evolved stars. When we compare the gravitational waves from the two realistic
equation of states, significant differences are not found, except that the
typical frequencies of the gravitational wave become slightly higher for the
softer equation of state.
