  We study the radio power of the core and its relation to the optical
properties of the host galaxy in samples of high excitation (HERG) and low
excitation (LERG) Fanaroff-Riley type II (FRII) radio galaxies. The radio
galaxy sample is divided into two groups of core/non-core FRII, based on the
existence of strong, weak or lack of single radio core component. We show that
FRII LERGs with radio emission of the core have significantly higher [O III]
line luminosities compared to the non-core LERG FRIIs. There is no significant
difference between the hosts of the core and non-core FRIIs of LERG type in
galaxy sizes, concentration indices, star formation rates, 4000-\AA\ break
strengths, colours, black hole masses and black hole to stellar masses. We show
that the results are not biased by the stellar masses, redshifts and angular
sizes of the radio galaxies. We argue that the detection of higher [O III]
luminosities in the core FRIIs may indicate the presence of higher amounts of
gas, very close to the AGN nucleus in the core FRIIs compared to the non-core
FRIIs or may result from the interaction of the radio jets with this gas. The
core and non-core FRIIs of the HERG type show no significant differences
perhaps due to our small sample size. The effect of relativistic beaming on the
radio luminosities and the contribution of restating AGN activity have also
been considered.
