Global hotstar wind models for stars from Magellanic Clouds
Abstract
We provide massloss 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 massloss rate) just from basic global stellar parameters. As a result of their lower metallicity, the line radiative driving is weaker leading to lower wind massloss rates with respect to the Galactic stars. We provide a formula that fits the massloss rate predicted by our models as a function of stellar luminosity and metallicity. On average, the massloss rate scales with metallicity as Ṁ Z^{0.59}. The predicted massloss rates are lower than massloss rates derived from Hα diagnostics and can be reconciled with observational results assuming clumping factor C_{c} = 9. On the other hand, the predicted massloss rates either agree or are slightly higher than the massloss 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 massloss rate determination, which can be used for quantitative study of stars from Magellanic Clouds.
 Publication:

Astronomy and Astrophysics
 Pub Date:
 April 2018
 DOI:
 10.1051/00046361/201731969
 arXiv:
 arXiv:1712.03321
 Bibcode:
 2018A&A...612A..20K
 Keywords:

 stars: winds;
 outflows;
 stars: massloss;
 stars: earlytype;
 Magellanic Clouds;
 hydrodynamics;
 radiative transfer;
 Astrophysics  Solar and Stellar Astrophysics
 EPrint:
 accepted for publication in A&