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

Abstract

Recent results strongly challenge the canonical picture of massive star winds: various evidence indicates that currently accepted mass-loss rates, Mdot, may need to be revised downwards significantly. This is because the most commonly used mass-loss diagnostics are affected by ``clumping'' (small-scale density inhomogeneities), influencing our interpretation of observed spectra and fluxes. Such downward revisions would have dramatic consequences for the evolution of, and feedback from, massive stars, and thus robust determinations of the clumping properties and mass-loss rates are urgently needed. Here, we present a first attempt to constrain the radial stratification of the so-called clumping factor. To this end, we have analyzed a sample of 19 Galactic O-type supergiants/giants, by combining data for Halpha, IR, mm and radio fluxes, and using appropriate analysis methods. Clumping has been included into our analysis in the ``conventional'' way, by assuming the inter-clump matter to be void. Because (almost) all our diagnostics depends on the square of density, we cannot derive absolute clumping factors, but only factors normalized to a certain minimum. This minimum was usually found to be located in the outermost, radio-emitting region, i.e., the radio mass-loss rates are the lowest ones, compared to Mdot derived from Halpha and the IR. The radio rates agree well with those predicted by theory, but are only upper limits, due to unknown clumping in the outer wind. Our most important result concerns a (physical) difference between denser and thinner winds: for denser winds, the innermost region is more strongly clumped than the outermost one (with a normalized clumping factor of 4.1+/-1.4), whereas thinner winds have similar clumping properties in the inner and outer regions.

40 pages, 17 figures, accepted by A&A

Cited by in corpus (108)

• Mass loss from hot massive stars
• The empirical metallicity dependence of the mass-loss rate of O- and early B-type stars
• Cygnus X-1 contains a 21-solar mass black hole -- implications for massive star winds
• The most massive stars in the Arches cluster
• Spitzer SAGE Infrared Photometry of Massive Stars in the Large Magellanic Cloud
• Neglecting the porosity of hot-star winds can lead to underestimating mass-loss rates
• Bright OB stars in the Galaxy IV. Stellar and wind parameters of early to late B supergiants
• The VLT-FLAMES survey of massive stars: Wind properties and evolution of hot massive stars in the LMC
• The VLT-FLAMES Tarantula Survey XVII. Physical and wind properties of massive stars at the top of the main sequence
• Towards a unified view of inhomogeneous stellar winds in isolated supergiant stars and supergiant high mass X-ray binaries
• The Effect of Porosity on X-ray Emission Line Profiles from Hot-Star Winds
• Statistical properties of a sample of periodically variable B-type supergiants - Evidence for opacity-driven gravity-mode oscillations
• High resolution X-ray spectroscopy of bright O type stars
• The R136 star cluster dissected with Hubble Space Telescope/STIS. III. The most massive stars and their clumped winds
• Theory and Diagnostics of Hot Star Mass Loss
• Why binary interaction does not necessarily dominate the formation of Wolf-Rayet stars at low metallicity
• On the role of the WNH phase in the evolution of very massive stars: Enabling the LBV instability with feedback
• Repeating fast radio burst 20201124A originates from a magnetar/Be star binary
• Modeling Ultraviolet Wind Line Variability in Massive Hot Stars
• Mass-loss and diffusion in subdwarf B stars and hot white dwarfs: do weak winds exist?
• Properties of WNh stars in the Small Magellanic Cloud: evidence for homogeneous evolution
• New predictions for radiation-driven, steady-state mass-loss and wind-momentum from hot, massive stars. I. Method and first results
• A new radio census of neutron star X-ray binaries
• 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
• A Clumping Independent Diagnostic of Stellar Mass-loss Rates: Rapid Clump Destruction in Adiabatic Colliding Winds
• No breakdown of the radiatively-driven wind theory in low-metallicity environments
• On the interaction of microquasar jets with stellar winds
• MOST detects corotating bright spots on the mid-O type giant ξ Persei
• Long term variability of Cygnus X-1: VII. Orbital variability of the focussed wind in Cyg X-1 / HDE 226868 system
• Stratified disc wind models for the AGN broad-line region: ultraviolet, optical and X-ray properties
• Modeling the early evolution of massive OB stars with an experimental wind routine
• Empirical mass-loss rates and clumping properties of Galactic early-type O supergiants
• Compact Binary Coalescences: Astrophysical Processes and Lessons Learned
• NLTE models of line-driven stellar winds III. Influence of X-ray radiation on wind structure of O stars
• Spectroscopic evolution of massive stars on the main sequence
• Non-thermal emission from secondary pairs in close TeV binary systems
• The Quintuplet Cluster II. Analysis of the WN stars
• Theoretical wind clumping predictions of OB supergiants from line-driven instability simulations across the bi-stability jump
• Testing the predicted mass-loss bi-stability jump at radio wavelengths
• Mass fluxes for O stars
• Atmospheric NLTE models for the spectroscopic analysis of blue stars with winds. V. Complete comoving frame transfer, and updated modeling of X-ray emission
• New mass-loss rates of B supergiants from global wind models
• Chandra X-ray spectroscopy of the focused wind in the Cygnus X-1 system III. Dipping in the low/hard state
• Rotation Measure Variations and Reversals of Repeating Fast Radio Bursts in Massive Binary Systems
• On the H$\alpha$ Behaviour of Blue Supergiants: Rise and Fall over the Bi-stability Jump
• Observational properties of massive black hole binary progenitors
• Upper Mass-Loss Limits and Clumping in the Intermediate and Outer Wind Regions of OB stars
• Correlation between the gas-phase metallicity and ionization parameter in extragalactic HII regions
• The Tarantula Massive Binary Monitoring V. R 144: a wind-eclipsing binary with a total mass > 140 Msun
• Clumping and X-Rays in cooler B supergiant stars
• Mass-loss rates of Very Massive Stars
• Central stars of planetary nebulae in the Galactic bulge
• New hydrodynamic solutions for line-driven winds of hot massive stars using Lambert $W$-function
• Self-consistent solutions for line-driven winds of hot massive stars. The m-CAK procedure
• X-Shooting ULLYSES: Massive Stars at low metallicity IX: Empirical constraints on mass-loss rates and clumping parameters for OB supergiants in the Large Magellanic Cloud
• Shock-heated radiation-driven outflows as a solution to the weak-wind problem of late O-type stars
• e-MERLIN 21cm constraints on the mass-loss rates of OB stars in Cyg OB2
• X-ray diagnostics of massive star winds
• The IACOB project XI. No increase of mass-loss rates over the bistability region
• The distance, rotation, and physical parameters of zeta Pup
• Stellar wind models of central stars of planetary nebulae
• Optical spectroscopy of the blue supergiant Sk-69 279 and its circumstellar shell with SALT
• ALMA observations of the supergiant B[e] star Wd1-9
• Empirical mass-loss rates and clumping properties of O-type stars in the LMC
• The Infrared Massive Stellar Content of M83
• Radio observations of candidate magnetic O stars
• Theoretical wind clumping predictions from 2D LDI models of O-star winds at different metallicities
• A Transparent Window into Early-Type Stellar Variability
• Using Shell Models to Investigate Clumping in the WN4 Star HD 50896
• Chandra grating spectroscopy of embedded wind shock X-ray emission from O stars shows low plasma temperatures and significant wind absorption
• Mid-infrared observations of O-type stars: spectral morphology
• Angular Sizes and Effective Temperatures of O-type Stars from Optical Interferometry with the CHARA Array
• A Deep Exposure in High Resolution X-Rays Reveals the Hottest Plasma in the $\zeta$Puppis Wind
• Expectations for Fast Radio Bursts in Neutron Star-Massive Star binaries
• A Radio Census of the Massive Stellar Cluster Westerlund 1
• Neon Abundances from a Spitzer/IRS Survey of Wolf-Rayet Stars
• Mass loss rates from mid-IR excesses in LMC and SMC O stars
• New self-consistent wind parameters fitting optical spectra of O-type stars observed with HERMES spectrograph
• The population synthesis of Wolf-Rayet stars involving binary merger channels
• Hot star wind models with new solar abundances
• Using Shell Models to Investigate Clumping in the Wind of the O7Iaf+ Supergiant AzV83
• Simulations of the line-driven instability in magnetic hot star winds
• Coordinated UV and X-ray spectroscopic observations of the O-type giant xi Per: the connection between X-rays and large-scale wind structure
• Towards early-type eclipsing binaries as extragalactic milestones: II. NLTE spectral analysis and stellar parameters of the detached O-type system OGLE-LMC-ECL-06782 in the LMC
• To clump or not to clump The impact of wind inhomogeneities on the optical and NIR spectroscopic analysis of massive OB stars
• Clumpy wind accretion in Cygnus X-1
• X-Shooting ULLYSES: massive stars at low metallicity: XII. The clumped winds of O-type (super)giants in the Large Magellanic Cloud
• The nature of the light variability of magnetic Of?p star HD 191612
• Moving inhomogeneous envelopes of stars
• X-ray irradiation of the stellar wind in HMXBs with B supergiants: Implications for ULXs
• How long can LBVs sleep? A long-term photometric vaiability and spectral study of the Galactic candidate luminous blue variable MN112
• Variable structures in the stellar wind of the HMXB Vela X-1
• Radio Variability from Co-Rotating Interaction Regions Threading Wolf-Rayet Winds
• On the importance of the wind emission to the optical continuum of OB supergiants
• Investigation of CygOB2 #11 (O5 Ifc) by modeling its atmosphere
• Ultraviolet Spectropolarimetry with Polstar: Clumping and Mass-loss Rate Corrections
• Structure formation in O-type stars and Wolf-Rayet stars
• COBRaS: The e-MERLIN 21 cm Legacy survey of Cygnus OB2
• Wray 15-906: a candidate luminous blue variable discovered with WISE, Herschel and SALT
• Observed epochal variations in X-ray lines from the O Supergiant $\zeta$ Puppis do not require substantial changes in the wind mass flux
• X-Shooting ULLYSES: Massive stars at low metallicity XV. On the metallicity dependence of B-supergiant mass-loss rates
• Low-frequency spectra of neutron star + OB supergiant binaries: Does wind density drive persistent and flaring modes of accretion?
• Wind structure of late B supergiants I. Multi-line analyses of near-surface and wind structure in HD 199 478 (B8 Iae)
• Stellar feedback and triggered star formation in the prototypical bubble RCW 120
• Fe XVII $2p$-$3s$ line ratio diagnostic of shock formation radius in O stars
• Radio Spectral Energy Distributions for Single Massive Star Winds with Free-Free and Synchrotron Emission
• Accretion in massive colliding wind binaries and the effect of wind momentum ratio
• ALMA measurements of mass loss and wind clumping in the massive stars of the Arches cluster