  We present new X-ray and radio observations of the WR star EZ CMa (HD 50896)
obtained with XMM-Newton and the VLA. This WN4 star shows optical/UV
variability at a period of 3.76 d whose cause is unknown. VLA flux measurements
at five frequencies show the radio spectral energy distribution is
well-described by a power law with spectral index +0.69 (+-0.05), as expected
for free-free wind emission. The derived ionized mass loss rate allowing for
distance uncertainties is M(dot) = 3.8 (+-2.6)e-5 M_sun/yr. The CCD X-ray
spectra show prominent Si XIII and S XV emission lines and can be acceptably
modeled as an absorbed multi-temperature optically thin plasma. Nonsolar
abundances are inferred with Fe notably deficient. The X-ray emission is
dominated by cool plasma at kT_cool = 0.6 keV, but a harder component is also
detected with a derived temperature kT_hot = 3.0 - 4.2 keV if the emission is
thermal. This is too high to be explained by radiative wind shock models and
the luminosity of the hard component is 3 orders of magnitude lower than
expected for accretion onto a neutron star companion. We argue that the hard
emission could be produced by the WR wind shocking onto a normal
(nondegenerate) stellar companion at close separation. Using comparable data
sets, we show that the X-ray and radio properties of EZ CMa are strikingly
similar to those of the WN5-6 star WR110. This similarity points to common
X-ray and radio emission processes in WN stars and discredits the idea that EZ
CMa is anomalous within its class.
