Issue |
A&A
Volume 663, July 2022
|
|
---|---|---|
Article Number | A40 | |
Number of page(s) | 7 | |
Section | Stellar atmospheres | |
DOI | https://doi.org/10.1051/0004-6361/202142844 | |
Published online | 11 July 2022 |
Theoretical wind clumping predictions from 2D LDI models of O-star winds at different metallicities
Institute of Astronomy, KU Leuven,
Celestijnenlaan 200D,
3001
Leuven, Belgium
e-mail: florian.driessen@kuleuven.be
Received:
6
December
2021
Accepted:
4
April
2022
Context. Hot, massive (OB) stars experience strong line-driven stellar winds and mass loss. As the majority of efficient driving lines are metallic, the amount of wind driving and mass loss is dependent on the stellar metallicity Z. In addition, line-driven winds are intrinsically inhomogeneous and clumpy. However, to date, neither theoretical nor empirical studies of line-driven winds have investigated how such wind clumping may also depend on Z.
Aims. We theoretically investigated the degree of wind clumping due to the line-deshadowing instability (LDI) as a function of Z
Methods. We performed two-dimensional hydrodynamic simulations of the LDI with an assumed one-dimensional radiation line force for a grid of O-star wind models with fixed luminosity, but with different metal contents by varying the accumulative line strength Q̄ describing the total ensemble of driving lines.
Results. We find that, for this fixed luminosity, the amount of wind clumping decreases with metallicity. The decrease is clearly seen in the statistical properties of our simulations, but is nonetheless rather weak; a simple power-law fit for the dependence of the clumping factor fcl ≡ 〈ρ2〉 / 〈ρ〉2 on metallicity yields fcl ∝ Z0.15±0.01. This implies that empirically derived power-law dependencies of mass-loss rate Ṁ on metallicity – which were previously inferred from spectral diagnostics effectively depending on Ṁ √fcl but without having any constraints on fcl(Z) – should be only modestly altered by clumping. We expect that this prediction can be directly tested using new data from the Hubble Space Telescope Ultraviolet Legacy Library of Young Stars as Essential Standards (ULLYSES) project.
Key words: stars: early-type / stars: winds / outflows / stars: mass-loss / instabilities
© F. A. Driessen et al. 2022
Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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