We discuss the possibility to obtain an electromagnetic emission accompanying
the gravitational waves emitted in the coalescence of a compact binary system.
Motivated by the existence of black hole configurations with open magnetic
field lines along the rotation axis, we consider a magnetic dipole in the
system, the evolution of which leads to (i) electromagnetic radiation, and (ii)
a contribution to the gravitational radiation, the luminosity of both being
evaluated. Starting from the observations on magnetars, we impose upper limits
for both the electromagnetic emission and the contribution of the magnetic
dipole to the gravitational wave emission. Adopting this model for the
evolution of neutron star binaries leading to short gamma ray bursts, we
compare the correction originated by the electromagnetic field to the
gravitational waves emission, finding that they are comparable for particular
values of the magnetic field and of the orbital radius of the binary system.
Finally we calculate the electromagnetic and gravitational wave energy outputs
which result comparable for some values of magnetic field and radius.Comment: 9 pages, 3 figures, to appear in Astroph. Sp.Scienc
