The X-ray emission of O-type stars was first discovered in the early days of the Einstein satellite .
Since then many different surveys have confirmed that the ratio of X-ray to bolometric luminosity in O-type stars is roughly constant , but there is a paucity of studies that account for detailed information on spectral and wind properties of O-stars .
Recently a significant sample of O stars within our Galaxy was spectroscopically identified and presented in the Galactic O-Star Spectroscopic Survey ( GOSS ) .
At the same time , a large high-fidelity catalog of X-ray sources detected by the XMM-Newton X-ray telescope was released .
Here we present the X-ray catalog of O stars with known spectral types and investigate the dependence of their X-ray properties on spectral type as well as stellar and wind parameters .
We find that , among the GOSS sample , 127 O-stars have a unique XMM-Newton source counterpart and a Gaia data release 2 ( DR2 ) association .
Terminal velocities are known for a subsample of 35 of these stars .
We confirm that the X-ray luminosities of dwarf and giant O stars correlate with their bolometric luminosity .
For the subsample of O stars with measure terminal velocities we find that the X-ray luminosities of dwarf and giant O stars also correlate with wind parameters .
However , we find that these correlations break down for supergiant stars .
Moreover , we show that supergiant stars are systematically harder in X-rays compared to giant and dwarf O-type stars .
We find that the X-ray luminosity depends on spectral type , but seems to be independent of whether the stars are single or in a binary system .
Finally , we show that the distribution of \log ( { L _ { X } } / { L _ { bol } } ) in our sample stars is non-Gaussian , with the peak of the distribution at \mbox { $ \log ( { L _ { X } } / { L _ { bol } } ) $ } \approx - 6.6 .