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arXiv · 2011.02310

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

J. Puls·F. Najarro·J. O. Sundqvist·K. Sen
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Abstract

Context. Obtaining precise stellar and wind properties and abundance patterns of massive stars is crucial to understanding their nature and interactions with their environments, as well as to constrain their evolutionary paths and end-products. Aims. To enable higher versatility and precision of the complete UV to optical range, we improve our NLTE atmosphere and spectrum synthesis code FASTWIND. We also aim to obtain an advanced description of X-ray emission from wind-embedded shocks. Methods. We include a detailed comoving frame radiative transfer for the essential frequency range, but still apply methods that enable low turnaround times. Results. In most cases, our new results agree excellently with those from the alternative code CMFGEN, both regarding the total radiative acceleration, strategic optical lines, and the UV-range. The agreement regarding NIII4634-4640-4642 has improved, though there are still certain discrepancies, mostly related to line overlap effects in the extreme ultraviolet. In the UV range of our coolest models, we find differences in the predicted depression of the pseudo-continuum, most pronounced around Ly_alpha. The comparison between our new and previous FASTWIND version reveals an almost perfect agreement, except for NV 4603-4619. Using an improved, depth-dependent description for the filling factors of hot, X-ray emitting material, we confirm previous analytic scaling relations with our numerical models. Conclusions. We warn against uncritically relying on transitions, which are strongly affected by direct or indirect line-overlap effects. The predicted UV-continuum depression for the coolest grid-models needs to be checked, both observationally, and regarding the underlying atomic data. Wind lines from "super-ionized" ions such as OVI can, in principle, be used to constrain the distribution of wind-embedded shocks.

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J. Puls, F. Najarro, J. O. Sundqvist, K. Sen. 2020-11-04. Atmospheric NLTE models for the spectroscopic analysis of blue stars with winds. V. Complete comoving frame transfer, and updated modeling of X-ray emission. https://doi.org/10.1051/0004-6361%2F202038464

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