To clump or not to clump The impact of wind inhomogeneities on the optical and NIR spectroscopic analysis of massive OB stars

Abstract

Winds of massive stars have density inhomogeneities (clumping) that may affect the formation of spectral lines in different ways, depending on their formation region. Most of previous and current spectroscopic analyses have been performed in the optical or ultraviolet domain. However, massive stars are often hidden behind dense clouds rendering near-infrared observations necessary. Our objective is to investigate whether a spectroscopic analysis using either optical or infrared observations results in the same stellar parameters with comparable accuracy, and whether clumping affects them in different ways. We analyzed optical and near-infrared observations of a set of massive O stars with spectral types O4-O9.5 and all luminosity classes. We obtain similar stellar parameters in the optical and the infrared, although with larger uncertainties in the near-infrared, both with and without clumping, albeit with some individual deviating cases. We find that the inclusion of clumping improves the fit to H${}_{\alpha }$ or HeII 4686 in the optical for supergiants, as well as that of Br${}_{\gamma }$ in the near-infrared, but it sometimes worsens the fit to HeII 2.18$\mu$m. Globally, there are no significant differences when using the clumping laws tested in this work. The infrared can be used for spectroscopic analyses, giving similar parameters as from the optical, though with larger uncertainties. The best fits to different lines are obtained with different (linear) clumping laws, indicating that the wind structure may be more complex than adopted in the present work. No clumping law results in a better global fit, or improves the consistency between optical and infrared stellar parameters. Our work shows that the optical and infrared lines are not sufficient to break the dichotomy between the mass-loss rate and clumping factor.

References in corpus (45)

• The chemical composition of the Sun
• Binary interaction dominates the evolution of massive stars
• Grids of stellar models with rotation - I. Models from 0.8 to 120 Msun at solar metallicity (Z = 0.014)
• Pre-Supernova Evolution of Massive Single and Binary Stars
• Mass loss from hot massive stars
• The rotation rates of massive stars: the role of binary interaction through tides, mass transfer and mergers
• Atmospheric NLTE-Models for the Spectroscopic Analysis of Blue Stars with Winds. II. Line-Blanketed Models
• The Discordance of Mass-Loss Estimates for Galactic O-Type Stars
• Quantitative Spectroscopy of O Stars at Low Metallicity. O Dwarfs in NGC 346
• Sub-surface convection zones in hot massive stars and their observable consequences
• The IACOB project: I. Rotational velocities in Northern Galactic O and early B-type stars revisited. The impact of other sources of line-broadening
• 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
• Massive runaways and walkaway stars
• The VLT-FLAMES Tarantula Survey XII. Rotational velocities of the single O-type stars
• A Porosity-Length Formalism for Photon-Tiring-Limited Mass Loss from Stars Above the Eddington Limit
• Revised Stellar Temperatures for Magellanic Cloud O Supergiants from FUSE and VLT-UVES Spectroscopy
• Neglecting the porosity of hot-star winds can lead to underestimating mass-loss rates
• Spectral models for binary products: Unifying Subdwarfs and Wolf-Rayet stars as a sequence of stripped-envelope stars
• A Medium Resolution Near-Infrared Spectral Atlas of O and Early B Stars
• Bright OB stars in the Galaxy IV. Stellar and wind parameters of early to late B supergiants
• Properties of Galactic early-type O-supergiants: A combined FUV-UV and optical analysis
• The VLT-FLAMES Tarantula Survey XVII. Physical and wind properties of massive stars at the top of the main sequence
• L-band spectroscopy of Galactic OB-stars
• Mass loss from inhomogeneous hot star winds II. Constraints from a combined optical/UV study
• Metallicity in the Galactic Center: The Quintuplet cluster
• Non-LTE line-formation for hydrogen revisited
• Mass loss from inhomogeneous hot star winds I. Resonance line formation in 2D models
• Properties of OB star-black hole systems derived from detailed binary evolution models
• Clumping in the inner winds of hot, massive stars from hydrodynamical line-driven instability simulations
• Macroclumping as solution of the discrepancy between Hα and P v mass loss diagnostics for O-type stars
• The IACOB project. V. Spectroscopic parameters of the O-type stars in the modern grid of standards for spectral classification
• Effects of close binary evolution on the main-sequence morphology of young star clusters
• Atmospheric NLTE-models for the spectroscopic analysis of blue stars with winds. IV. Porosity in physical and velocity space
• Quantitative H and K band spectroscopy of Galactic OB-stars at medium resolution
• The IACOB project: A grid-based automatic tool for the quantitative spectroscopic analysis of O-stars
• Bright OB stars in the Galaxy.II. Wind variability in O supergiants as traced by H-alpha
• 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 VLT-FLAMES Tarantula Survey XXVI: Properties of the O-dwarf population in 30 Doradus
• The IACOB project. VII. The rotational properties of Galactic massive O-type stars revisited
• The VLT-FLAMES Tarantula Survey. XIII: On the nature of O Vz stars in 30 Doradus
• A pseudo-planar, periodic-box formalism for modelling the outer evolution of structure in spherically expanding stellar winds
• Empirical mass-loss rates and clumping properties of Galactic early-type O supergiants
• The temperature dependency of Wolf-Rayet-type mass loss: An exploratory study for winds launched by the hot iron bump
• Upper Mass-Loss Limits and Clumping in the Intermediate and Outer Wind Regions of OB stars
• Atmospheres and Winds of PN Central Stars

Cited by in corpus (2)

• X-Shooting ULLYSES: Massive stars at low metallicity. IV. Spectral analysis methods and exemplary results for O stars
• Improving 1D stellar atmosphere models with insights from multi-dimensional simulations I. 1D vs 2D stratifications and spectral comparison for O stars