  We present the results of a spectral and timing analysis of PSR 0656+14 based
on the complete set of ROSAT observations carried out with the PSPC instrument
in 1991 and 1992. The present analysis confirms the thermal origin of the bulk
of the emission in the soft X-ray band (Finley et al. 1992). In addition, we
find strong evidence of a harder component, described equally well with a
blackbody at T about 2x10^6 K, or with a steep power law with photon index
Gamma about 4.5. This bimodal emission is also supported by an analysis of the
light curve shape as a function of the energy. The 0.1--2.4 keV light curve of
PSR 0656+14, with a pulsed fraction of about 9%, is interpreted with a simple
model for the temperature distribution on the neutron star surface, coupled
with the geometrical information derived from radio data. In this model, which
includes the effects of relativistic light bending and gravitational redshift,
the X--rays originate from two thermal components resulting from neutron star
cooling and blackbody emission released in the hotter polar cap regions. The
observed modulation can be reproduced only if PSR 0656+14 has a relatively high
dipole inclination (about 30 deg) and (1+z) is less than about 1.15. The
overall pulsed fraction cannot be significantly increased by including the
polar cap contribution, if its temperature and intensity are to be consistent
with the observed spectra.
