Volume 648, April 2021
|Number of page(s)||16|
|Published online||08 April 2021|
New predictions for radiation-driven, steady-state mass-loss and wind-momentum from hot, massive stars
II. A grid of O-type stars in the Galaxy and the Magellanic Clouds
KU Leuven, Instituut voor Sterrenkunde,
Celestijnenlaan 200D, 3001 Leuven, Belgium
2 LMU München, Universitätssternwarte, Scheinerstr. 1, 81679 München, Germany
3 Centro de Astrobiologia, Instituto Nacional de Tecnica Aerospacial, 28850 Torrejon de Ardoz, Madrid, Spain
Accepted: 12 August 2020
Context. Reliable predictions of mass-loss rates are important for massive-star evolution computations.
Aims. We aim to provide predictions for mass-loss rates and wind-momentum rates of O-type stars, while carefully studying the behaviour of these winds as functions of stellar parameters, such as luminosity and metallicity.
Methods. We used newly developed steady-state models of radiation-driven winds to compute the global properties of a grid of O-stars. The self-consistent models were calculated by means of an iterative solution to the equation of motion using full non-local thermodynamic equilibrium radiative transfer in the co-moving frame to compute the radiative acceleration. In order to study winds in different galactic environments, the grid covers main-sequence stars, giants, and supergiants in the Galaxy and both Magellanic Clouds.
Results. We find a strong dependence of mass-loss on both luminosity and metallicity. Mean values across the grid are Ṁ~L*2.2 and Ṁ~L*0.95; however, we also find a somewhat stronger dependence on metallicity for lower luminosities. Similarly, the mass loss-luminosity relation is somewhat steeper for the Small Magellanic Cloud (SMC) than for the Galaxy. In addition, the computed rates are systematically lower (by a factor 2 and more) than those commonly used in stellar-evolution calculations. Overall, our results are in good agreement with observations in the Galaxy that properly account for wind-clumping, with empirical Ṁ versus Z* scaling relations and with observations of O-dwarfs in the SMC.
Conclusions. Our results provide simple fit relations for mass-loss rates and wind momenta of massive O-stars stars as functions of luminosity and metallicity, which are valid in the range Teff = 28 000–45 000 K. Due to the systematically lower values for Ṁ, our new models suggest that new rates might be needed in evolution simulations of massive stars.
Key words: stars: atmospheres / stars: early-type / stars: massive / stars: mass-loss / stars: winds, outflows / Magellanic Clouds
© ESO 2021
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