Issue |
A&A
Volume 642, October 2020
|
|
---|---|---|
Article Number | A172 | |
Number of page(s) | 29 | |
Section | Stellar atmospheres | |
DOI | https://doi.org/10.1051/0004-6361/202038464 | |
Published online | 19 October 2020 |
Atmospheric NLTE models for the spectroscopic analysis of blue stars with winds
V. Complete comoving frame transfer, and updated modeling of X-ray emission
1
LMU München, Universitätssternwarte,
Scheinerstr. 1,
81679
München,
Germany
e-mail: uh101aw@usm.uni-muenchen.de
2
Departamento de Astrofísica, Centro de Astrobiología (CSIC-INTA),
Ctra. Torrejón a Ajalvir km 4,
28850
Torreón de Ardoz,
Spain
3
KU Leuven, Instituut voor Sterrenkunde,
Celestijnenlaan 200D,
3001
Leuven,
Belgium
4
Argelander Institut für Astronomie der Universität Bonn,
Auf dem Hügel 71,
53121
Bonn,
Germany
Received:
22
May
2020
Accepted:
3
August
2020
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 ultraviolet (UV) to optical range, we improve our high-performance, unified, NLTE atmosphere and spectrum synthesis code FASTWIND. Moreover, we aim to obtain an advanced description of X-ray emission from wind-embedded shocks, consistent with alternative modeling approaches.
Methods. We include a detailed comoving frame radiative transfer for the essential frequency range, but still apply methods that enable low turnaround times. We compare the results of our updated computations with those from the alternative code CMFGEN, and our previous FASTWIND version, for a representative model grid.
Results. In most cases, our new results agree excellently with those from CMFGEN, both regarding the total radiative acceleration, strategic optical lines, and the UV-range. Moderate differences concern He II λλ4200-4541 and N V λλ4603-4619. The agreement regarding N III λλ4634−4640−4642 has improved, though there are still certain discrepancies, mostly related to line overlap effects in the extreme ultraviolet, depending on abundances and micro-turbulence. In the UV range of our coolest models, we find differences in the predicted depression of the pseudo-continuum, which is most pronounced around Lyα. This depression is larger in CMFGEN, and related to different Fe IV atomic data. The comparison between our new and previous FASTWIND version reveals an almost perfect agreement, except again for N V λλ4603-4619. 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 O VI can, in principle, be used to constrain the distribution of wind-embedded shocks. The new FASTWIND version v11 is now ready to be used.
Key words: methods: numerical / stars: atmospheres / stars: early-type / stars: massive / X-rays: stars
© ESO 2020
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.