Context : HD 54662 is an O-type binary star belonging to the CMa OB1 association .
Because of its long-period orbit , this system is an interesting target to test the adiabatic wind shock model .

Aims : The goal of this study is to improve our knowledge of the orbital and stellar parameters of HD 54662 and to analyze its X-ray emission to test the theoretical scaling of X-ray emission with orbital separation for adiabatic wind shocks .

Methods : We applied a spectral disentangling code to a set of optical spectra to determine the radial velocities and the individual spectra of the primary and secondary stars .
The orbital solution of the system was established and the reconstructed individual spectra were analyzed by means of the CMFGEN model atmosphere code .
We fitted two X-ray spectra using a Markov Chain Monte Carlo algorithm and compared these spectra to the emission expected from adiabatic shocks .

Results : We determine an orbital period of 2103.4 days , a surprisingly low orbital eccentricity of 0.11 , and a mass ratio m _ { 2 } / m _ { 1 } of 0.84 .
Combined with the orbital inclination inferred in a previous astrometric study , we obtain surprisingly low masses of 9.7 and 8.2 M _ { \odot } { } .
From the disentangled primary and secondary spectra , we infer O6.5 spectral types for both stars , of which the primary is about two times brighter than the secondary .
The softness of the X-ray spectra for the two observations , the very small variation of best-fitting spectral parameters , and the comparison of the X-ray-to-bolometric luminosity ratio with the canonical value for O-type stars allow us to conclude that X-ray emission from the wind interaction region is quite low and that the observed emission is rather dominated by the intrinsic emission from the stars .
We can not confirm the runaway status previously attributed to HD 54662 by computing the peculiar radial and tangential velocities .
We find no X-ray emission associated with the bow shock detected in the infrared .

Conclusions : The lack of hard X-ray emission from the wind-shock region suggests that the mass-loss rates are lower than expected and/or that the pre-shock wind velocities are much lower than the terminal wind velocities .
The bow shock associated with HD 54662 possibly corresponds to a wind-blown arc created by the interaction of the stellar winds with the ionized gas of the CMa OB1 association rather than by a large differential velocity between the binary and the surrounding interstellar medium .