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

Abstract

Context: The star cluster R136 inside the LMC 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: To observationally constrain the stellar and wind properties of the massive stars in R136, in particular the parameters related to wind clumping. Methods: We simultaneously analyse optical and UV spectroscopy of 53 O-type and 3 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 these 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 derive an initial stellar mass of $\ge 250{\mathrm{M}}_{\odot }$ for the most massive star in our sample, R136a1. The winds of our sample stars are highly clumped, with an average clumping factor of $f_{\mathrm{cl}}=29\pm 15$. We find tentative trends in the wind-structure parameters as a function of 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 reproduces both quantities. The prescription of Krtička & Kubát (2018) matches best the observed mass-loss rates.

Accepted for publication in A&A; Appendix I will not be included in the published version

References in corpus (44)

• Pre-Supernova Evolution of Massive Single and Binary Stars
• A distance to the Large Magellanic Cloud that is precise to one per cent
• Mass loss from hot massive stars
• The R136 star cluster hosts several stars whose individual masses greatly exceed the accepted 150 Msun stellar mass limit
• Primordial Star Formation under the Influence of Far Ultraviolet Radiation: 1540 Cosmological Halos and the Stellar Mass Distribution
• An excess of massive stars in the local 30 Doradus starburst
• Bright OB stars in the Galaxy - III. Constraints on the radial stratification of the clumping factor in hot star winds from a combined Halpha, IR and radio analysis
• Before the first supernova: combined effects of HII regions and winds on molecular clouds
• The VLT-FLAMES survey of massive stars: rotation and nitrogen enrichment as the key to understanding massive star evolution
• Neglecting the porosity of hot-star winds can lead to underestimating mass-loss rates
• BONNSAI: a Bayesian tool for comparing stars with stellar evolution models
• The VLT-FLAMES survey of massive stars: Mass loss and rotation of early-type stars in the SMC
• The evolution of rotating very massive stars with LMC composition
• The VLT-FLAMES survey of massive stars: Wind properties and evolution of hot massive stars in the LMC
• An XMM-Newton view of the young open cluster NGC 6231 -- II. The OB star population
• The VLT-FLAMES Tarantula Survey XVII. Physical and wind properties of massive stars at the top of the main sequence
• The IACOB project: III. New observational clues to understand macroturbulent broadening in massive O- and B-type stars
• 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
• Voigt Profile Fitting to Quasar Absorption Lines: An Analytic Approximation to the Voigt-Hjerting Function
• Testing massive star evolution, star-formation history and feedback at low metallicity : Spectroscopic analysis of OB stars in the SMC Wing
• Transition of the initial mass function in the metal-poor environments
• The R136 star cluster dissected with Hubble Space Telescope/STIS. II. Physical properties of the most massive stars in R136
• The MiMeS Survey of Magnetism in Massive Stars: CNO surface abundances of Galactic O stars
• Evolution of surface CNO abundances in massive stars
• Metallicity-dependent wind parameter predictions for OB stars
• New predictions for radiation-driven, steady-state mass-loss and wind-momentum from hot, massive stars. I. Method and first results
• Grids of stellar models with rotation VI: Models from 0.8 to 120 $M_{\odot }$ at a metallicity Z = 0.006
• Mass loss from inhomogeneous hot star winds III. An effective-opacity formalism for line radiative transfer in accelerating, clumped two-component media, and first results on theory and diagnostics
• The properties of ten O-type stars in the low-metallicity galaxies IC 1613, WLM and NGC 3109
• Mass loss and the Eddington parameter: a new mass-loss recipe for hot and massive stars
• Empirical mass-loss rates and clumping properties of Galactic early-type O supergiants
• On the Importance of the Interclump Medium for Superionization: O VI Formation in the Wind of Zeta Pup
• NLTE models of line-driven stellar winds III. Influence of X-ray radiation on wind structure of O stars
• Stochastic Low Frequency Variability in 3-Dimensional Radiation Hydrodynamical Models of Massive Star Envelopes
• Theoretical wind clumping predictions of OB supergiants from line-driven instability simulations across the bi-stability jump
• Forming clusters within clusters: How 30 Doradus recollapsed and gave birth again
• Atmospheric NLTE models for the spectroscopic analysis of blue stars with winds. V. Complete comoving frame transfer, and updated modeling of X-ray emission
• Constraining the Overcontact Phase in Massive Binary Evolution I. Mixing in V382 Cyg, VFTS 352, and OGLE SMC-SC10 108086
• Physics and evolution of the most massive stars in 30 Dor. Mass loss, envelope inflation, and a variable upper stellar mass limit
• Upper Mass-Loss Limits and Clumping in the Intermediate and Outer Wind Regions of OB stars
• Mass-loss rates of Very Massive Stars
• Mapping the core of the Tarantula Nebula with VLT-MUSE II. The spectroscopic Hertzsprung-Russell diagram of OB stars in NGC 2070
• High contrast and resolution near infrared photometry of the core of R136
• Giant Molecular Cloud Formation at the Interface of Colliding Supershells in the Large Magellanic Cloud