Coupling hydrodynamics with comoving frame radiative transfer
- Aims. To gain a realistic picture of the donor star in Vela X-1, we constructed a hydrodynamically consistent atmosphere model describing the wind stratification while properly reproducing the observed donor spectrum. To investigate how X-ray illumination affects the stellar wind, we calculated additional models for different X-ray luminosity regimes. Methods. We used the recently updated version of the Potsdam Wolf-Rayet code to consistently solve the hydrodynamic equation together with the statistical equations and the radiative transfer. Results. The wind flow in Vela X-1 is driven by ions from various elements, with Fe III and S III leading in the outer wind. The model-predicted mass-loss rate is in line with earlier empirical studies. The mass-loss rate is almost unaffected by the presence of the accreting NS in the wind. The terminal wind velocity is confirmed at u(infinity) approximate to 600 km s(-1). On the other hand, the wind velocity in the inner region where the NS is located is only approximate to 100 km s(-1), which isAims. To gain a realistic picture of the donor star in Vela X-1, we constructed a hydrodynamically consistent atmosphere model describing the wind stratification while properly reproducing the observed donor spectrum. To investigate how X-ray illumination affects the stellar wind, we calculated additional models for different X-ray luminosity regimes. Methods. We used the recently updated version of the Potsdam Wolf-Rayet code to consistently solve the hydrodynamic equation together with the statistical equations and the radiative transfer. Results. The wind flow in Vela X-1 is driven by ions from various elements, with Fe III and S III leading in the outer wind. The model-predicted mass-loss rate is in line with earlier empirical studies. The mass-loss rate is almost unaffected by the presence of the accreting NS in the wind. The terminal wind velocity is confirmed at u(infinity) approximate to 600 km s(-1). On the other hand, the wind velocity in the inner region where the NS is located is only approximate to 100 km s(-1), which is not expected on the basis of a standard beta-velocity law. In models with an enhanced level of X-rays, the velocity field in the outer wind can be altered. If the X-ray flux is too high, the acceleration breaks down because the ionization increases. Conclusions. Accounting for radiation hydrodynamics, our Vela X-1 donor atmosphere model reveals a low wind speed at the NS location, and it provides quantitative information on wind driving in this important HMXB.…
Author details: | Andreas Alexander Christoph SanderORCiDGND, F. Fürst, P. Kretschmar, Lidia M. OskinovaORCiDGND, Helge Tobias TodtORCiD, Rainer HainichGND, Tomer ShenarORCiDGND, Wolf-Rainer HamannORCiDGND |
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DOI: | https://doi.org/10.1051/0004-6361/201731575 |
ISSN: | 1432-0746 |
Title of parent work (English): | Astronomy and astrophysics : an international weekly journal |
Subtitle (English): | Stellar wind stratification in the high-mass X-ray binary Vela X-1 |
Publisher: | EDP Sciences |
Place of publishing: | Les Ulis |
Publication type: | Article |
Language: | English |
Date of first publication: | 2018/02/28 |
Publication year: | 2018 |
Release date: | 2022/01/19 |
Tag: | X-rays: binaries; stars: atmospheres; stars: early-type; stars: mass-loss; stars: massive; stars: winds, outflows |
Volume: | 610 |
Number of pages: | 19 |
Funding institution: | Deutsche Forschungsgemeinschaft (DFG)German Research Foundation (DFG) [HA 1455/26]; German "Verbundforschung" (DLR) [50 OR 1612]; International Space Science Institute at Bern, Switzerland; Faculty of the European Space Astronomy Centre (ESAC) |
Organizational units: | Mathematisch-Naturwissenschaftliche Fakultät / Institut für Physik und Astronomie |
DDC classification: | 5 Naturwissenschaften und Mathematik / 52 Astronomie / 520 Astronomie und zugeordnete Wissenschaften |
5 Naturwissenschaften und Mathematik / 53 Physik / 530 Physik | |
Peer review: | Referiert |
Publishing method: | Open Access / Bronze Open-Access |