TY - JOUR
T1 - The R136 star cluster dissected with Hubble Space Telescope/STIS
T2 - III. The most massive stars and their clumped winds
AU - Brands, Sarah A.
AU - De Koter, Alex
AU - Bestenlehner, Joachim M.
AU - Crowther, Paul A.
AU - Sundqvist, Jon O.
AU - Puls, Joachim
AU - Caballero-Nieves, Saida M.
AU - Abdul-Masih, Michael
AU - Driessen, Florian A.
AU - García, Miriam
AU - Geen, Sam
AU - Gräfener, Götz
AU - Hawcroft, Calum
AU - Kaper, Lex
AU - Keszthelyi, Zsolt
AU - Langer, Norbert
AU - Sana, Hugues
AU - Schneider, Fabian R.N.
AU - Shenar, Tomer
AU - Vink, Jorick S.
N1 - Publisher Copyright: © Copyright 2022, Mary Ann Liebert, Inc., publishers 2022.
PY - 2022/7/1
Y1 - 2022/7/1
N2 - Context. The star cluster R136 inside the Large Magellanic Cloud hosts a rich population of massive stars, including the most massive stars known. The strong stellar winds of these very luminous stars impact their evolution and the surrounding environment. We currently lack detailed knowledge of the wind structure that is needed to quantify this impact. Aims. Our goal is to observationally constrain the stellar and wind properties of the massive stars in R136, in particular the wind-structure parameters related to wind clumping. 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 Ma 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 Krticka & Kubát (2018) matches the observed mass-loss rates best.
AB - Context. The star cluster R136 inside the Large Magellanic Cloud hosts a rich population of massive stars, including the most massive stars known. The strong stellar winds of these very luminous stars impact their evolution and the surrounding environment. We currently lack detailed knowledge of the wind structure that is needed to quantify this impact. Aims. Our goal is to observationally constrain the stellar and wind properties of the massive stars in R136, in particular the wind-structure parameters related to wind clumping. 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 Ma 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 Krticka & Kubát (2018) matches the observed mass-loss rates best.
KW - Galaxies: star clusters: individual: R136
KW - Magellanic Clouds
KW - Outflows
KW - Stars: fundamental parameters
KW - Stars: mass-loss
KW - Stars: massive
KW - Stars: winds
UR - http://www.scopus.com/inward/record.url?scp=85134465655&partnerID=8YFLogxK
U2 - 10.1051/0004-6361/202142742
DO - 10.1051/0004-6361/202142742
M3 - مقالة
SN - 0004-6361
VL - 663
JO - Astronomy and Astrophysics
JF - Astronomy and Astrophysics
M1 - A36
ER -