Global hot-star wind models for stars from Magellanic Clouds

2017/12/09 by Jiřı́ Krtička, Jiri Krticka, J. Kubát +1 · 35 citations
Physics and Astronomy · #Astronomy #Astronomy and Astrophysical Research #Astrophysics #Astrophysics and Star Formation Studies #Hydrostatic equilibrium #Metallicity #O-type star #Physics #Radiative transfer #Stars #Stellar, planetary, and galactic studies #Supergiant #astro-ph.SR

paper · pdf · doi:10.1051/0004-6361/201731969

published in Astronomy and Astrophysics 612, A20 (EDP Sciences) · accepted for publication in A&A, 12 pages, 8 figures

arxiv created 2017/12/09 · openalex publication_date 2017/12/11 · arxiv updated 2018/04/25 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/06

Abstract

We provide mass-loss rate predictions for O stars from Large and Small Magellanic Clouds. We calculate global (unified, hydrodynamic) model atmospheres of main sequence, giant, and supergiant stars for chemical composition corresponding to Magellanic Clouds. The models solve radiative transfer equation in comoving frame, kinetic equilibrium equations (also known as NLTE equations), and hydrodynamical equations from (quasi-)hydrostatic atmosphere to expanding stellar wind. The models allow us to predict wind density, velocity, and temperature (consequently also the terminal wind velocity and the mass-loss rate) just from basic global stellar parameters. As a result of their lower metallicity, the line radiative driving is weaker leading to lower wind mass-loss rates with respect to the Galactic stars. We provide a formula that fits the mass-loss rate predicted by our models as a function of stellar luminosity and metallicity. On average, the mass-loss rate scales with metallicity as Ṁ ~ Z 0.59 . The predicted mass-loss rates are lower than mass-loss rates derived from H α diagnostics and can be reconciled with observational results assuming clumping factor C c = 9. On the other hand, the predicted mass-loss rates either agree or are slightly higher than the mass-loss rates derived from ultraviolet wind line profiles. The calculated P v ionization fractions also agree with values derived from observations for LMC stars with T eff ≤ 40 000 K. Taken together, our theoretical predictions provide reasonable models with consistent mass-loss rate determination, which can be used for quantitative study of stars from Magellanic Clouds.

Citations

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• The Chemical Composition of the Sun
• Mass loss from late-type WN stars and itsZ-dependence