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The R136 star cluster dissected with Hubble Space Telescope/STIS: III. The most massive stars and their clumped winds

Methods. We simultaneously analyse optical and ultraviolet spectroscopy of 53 O-type and three WNh-stars using the FASTWIND model atmosphere code and a genetic algorithm. The models account for optically thick clumps and effects related to porosity and velocity-porosity, as well as a non-void interc...

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Main Authors: Brands, Sarah A. (Author) , de Koter, Alex (Author) , Bestenlehner, Joachim M. (Author) , Crowther, Paul A. (Author) , Sundqvist, Jon O. (Author) , Puls, Joachim (Author) , Caballero-Nieves, Saida M. (Author) , Abdul-Masih, Michael (Author) , Driessen, Florian A. (Author) , García, Miriam (Author) , Geen, Sam (Author) , Gräfener, Götz (Author) , Hawcroft, Calum (Author) , Kaper, Lex (Author) , Keszthelyi, Zsolt (Author) , Langer, Norbert (Author) , Sana, Hugues (Author) , Schneider, Fabian (Author) , Shenar, Tomer (Author) , Vink, Jorick S. (Author)
Format: Article (Journal)
Language:English
Published: 19 July 2022
In: Astronomy and astrophysics
Year: 2022, Volume: 663, Pages: 1-44
ISSN:1432-0746
DOI:10.1051/0004-6361/202142742
Online Access:Verlag, kostenfrei, Volltext: https://doi.org/10.1051/0004-6361/202142742
Verlag, kostenfrei, Volltext: https://www.aanda.org/10.1051/0004-6361/202142742
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Author Notes:Sarah A. Brands, Alex de Koter, Joachim M. Bestenlehner, Paul A. Crowther, Jon O. Sundqvist, Joachim Puls, Saida M. Caballero-Nieves, Michael Abdul-Masih, Florian A. Driessen, Miriam García, Sam Geen, Götz Gräfener, Calum Hawcroft, Lex Kaper, Zsolt Keszthelyi, Norbert Langer, Hugues Sana, Fabian R. N. Schneider, Tomer Shenar, and Jorick S. Vink
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Summary:Methods. We simultaneously analyse optical and ultraviolet spectroscopy of 53 O-type and three WNh-stars using the FASTWIND model atmosphere code and a genetic algorithm. The models account for optically thick clumps and effects related to porosity and velocity-porosity, as well as a non-void interclump medium. - Results. We obtain stellar parameters, surface abundances, mass-loss rates, terminal velocities, and clumping characteristics and compare them to theoretical predictions and evolutionary models. The clumping properties include the density of the interclump medium and the velocity-porosity of the wind. For the first time, these characteristics are systematically measured for a wide range of effective temperatures and luminosities. - Conclusions. We confirm a cluster age of 1.0-2.5 Myr and derived an initial stellar mass of ≥250 M for the most massive star in our sample, R136a1. The winds of our sample stars are highly clumped, with an average clumping factor of fcl = 29 ± 15. We find tentative trends in the wind-structure parameters as a function of the mass-loss rate, suggesting that the winds of stars with higher mass-loss rates are less clumped. We compare several theoretical predictions to the observed mass-loss rates and terminal velocities and find that none satisfactorily reproduce both quantities. The prescription of Krticˇka & Kubát (2018) matches the observed mass-loss rates best.
Item Description:Gesehen am 20.9.2022
Physical Description:Online Resource
ISSN:1432-0746
DOI:10.1051/0004-6361/202142742

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