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Context. Obtaining precise stellar and wind properties and abundance patternsof massive stars is crucial to understanding their nature and interactions withtheir environments, as well as to constrain their evolutionary paths andend-products.  Aims. To enable higher versatility and precision of the complete UV tooptical range, we improve our NLTE atmosphere and spectrum synthesis codeFASTWIND. We also aim to obtain an advanced description of X-ray emission fromwind-embedded shocks.  Methods. We include a detailed comoving frame radiative transfer for theessential frequency range, but still apply methods that enable low turnaroundtimes.  Results. In most cases, our new results agree excellently with those from thealternative code CMFGEN, both regarding the total radiative acceleration,strategic optical lines, and the UV-range. The agreement regardingNIII4634-4640-4642 has improved, though there are still certain discrepancies,mostly related to line overlap effects in the extreme ultraviolet. In the UVrange of our coolest models, we find differences in the predicted depression ofthe pseudo-continuum, most pronounced around Ly_alpha. The comparison betweenour new and previous FASTWIND version reveals an almost perfect agreement,except for NV 4603-4619. Using an improved, depth-dependent description for thefilling factors of hot, X-ray emitting material, we confirm previous analyticscaling relations with our numerical models.  Conclusions. We warn against uncritically relying on transitions, which arestrongly affected by direct or indirect line-overlap effects. The predictedUV-continuum depression for the coolest grid-models needs to be checked, bothobservationally, and regarding the underlying atomic data. Wind lines from"super-ionized" ions such as OVI can, in principle, be used to constrain thedistribution of wind-embedded shocks.

astronomy and astrophysics

Atmospheric NLTE models for the spectroscopic analysis of blue stars  with winds. V. Complete comoving frame transfer, and updated modeling of  X-ray emission