The Discordance of Mass-Loss Estimates for Galactic O-Type Stars

By A. Fullerton, D. Massa, R. Prinja. 2005

263 citations recorded by the source corpus.

We have determined accurate values of the product of the mass-loss rate and the ion fraction of P+4, Ṁq(P+4), for a sample of 40 Galactic O-type stars by fitting stellar wind profiles to observations of the P V resonance doublet obtained with FUSE, ORFEUS BEFS, and Copernicus. When P+4 is the dominant ion in the wind [i.e., 0.5 ≲ q(P+4) ≤ 1], Ṁq(P+4) approximates the mass-loss rate to within a factor of ≲2. Theory predicts that P+4 is the dominant ion in the winds of O7-O9.7 stars, although an empirical estimator suggests that the range O4-O7 may be more appropriate. However, we find that the mass-loss rates obtained from P V wind profiles are systematically smaller than those obtained from fits to Hα emission profiles or radio free-free emission by median factors of ~130 (if P+4 is dominant between O7 and O9.7) or ~20 (if P+4 is dominant between O4 and O7). These discordant measurements can be reconciled if the winds of O stars in the relevant temperature range are strongly clumped on small spatial scales. We use a simplified two-component model to investigate the volume filling factors of the denser regions. This clumping implies that mass-loss rates determined from "ρ2" diagnostics have been systematically overestimated by factors of 10 or more, at least for a subset of O stars. Reductions in the mass-loss rates of this size have important implications for the evolution of massive stars and quantitative estimates of the feedback that hot-star winds provide to their interstellar environments.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/486db957ddea4f495301d7d03c4baf4086667b43

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Citations in the corpus

THE TYPE IIb SUPERNOVA 2011dh FROM A SUPERGIANT PROGENITOR (2012, background): “The upper limit of the main-sequence mass may be even larger according to recent stellar wind massloss rates (see Bouret et al. 2005; Eldridge & Vink 2006; Fullerton et al. 2006).”
On the Role of Continuum-driven Eruptions in the Evolution of Very Massive Stars and Population III Stars (2006, background): “Recent efforts have thus focused on using diagnostics that scale linearly with density, such as UV resonance absorption lines; Fullerton et al. (2006) have suggested a reduction of 10–20 or more from traditional mass-loss rates, while Bouret et al. (2005) require reductions by factors of 3 or more…”
The empirical metallicity dependence of the mass-loss rate of O- and early B-type stars (2007, background): “…spectroscopy of He ii λ4686 in ζ Pup, and by Crowther et al. (2002); Hillier et al. (2003); Bouret et al. (2003); Massa et al. (2003); Martins et al. (2004, 2005); Bouret et al. (2005), and Fullerton et al. (2006) from analysis of UV (resonance) lines, partly in combination with optical lines.”
Mass Loss: Its Effect on the Evolution and Fate of High-Mass Stars (2014, background): “Using UV resonance absorption lines in O-type stars, Fullerton et al. (2006) have proposed a reduction by a factor of 10 or more from traditional mass-loss rates (fcl values of 100 or more), while Bouret et al. (2005) require reductions by factors of ∼3.”
High-mass X-ray binaries in the Milky Way (2013, background): “Besides multiple observational evidence (Bouret et al. 2005; Fullerton et al. 2006; Prinja & Howarth 1986; L’epine & Moffat 1999; Markova et al. 2005; Lupie & Nordsieck 1987; Davies et al. 2007; Cassinelli & Olson 1979; Oskinova et al. 2006), wind clumping is still poorly constrained.”
SN 2006gy: Discovery of the Most Luminous Supernova Ever Recorded, Powered by the Death of an Extremely Massive Star like η Carinae (2006, background): “…studies of line-drivenwinds from O-type stars andWR stars have shown that their winds are highly clumped, requiring that their mass-loss rates through line-driven winds on themain sequence could be an order ofmagnitude lower than previously believed (Fullerton et al. 2006; Bouret et al. 2005).”
Observed Fractions of Core-Collapse Supernova Types and Initial Masses of their Single and Binary Progenitor Stars (2010, background): “Recent work (Bouret et al. 2005; Fullerton et al. 2006; Puls et al. 2006) has demonstrated that O-star winds are clumped and that their mass-loss rates are too weak, so it appears likely that LBV giant eruptions must dominate this mass-loss if WR stars are to form via single-star evolution (Smith &…”
Neglecting the porosity of hot-star winds can lead to underestimating mass-loss rates (2007, methodology): “Considering the eff ct of clumping on UV resonance lines, Massa et al. (2003) and Fullerton et al. (2006) discuss how porosity can affect the formation of P Cygni lines and, in extreme cases, produce an apparently unsaturated profile for a line that would be extremely saturated if the wind material…”
Bright OB stars in the Galaxy. III. Constraints on the radial stratification of the clumping factor (2006, background): “It also agrees well with recent findings from Fullerton et al. (2006).”
The most massive stars in the Arches cluster (2007, background): “Values off as low as 0.01 have been derived by Bouret et al. (2005); Martins et al. (2005b); Fullerton et al. (2006).”
BLACK HOLE FORMATION IN FAILING CORE-COLLAPSE SUPERNOVAE (2010, background): “Recent observational results suggest that the rates used in current stellar evolution models may be too high by factors of 3− 10 if clumped winds are considered correctly (Bouret et al. 2005; Fullerton et al. 2006; Puls et al. 2006).”
Mass loss from late-type WN stars and its Z-dependence: very massive stars approaching the Eddington limit (2008, background): “Note that significant clumping factors in the range of D=10–100 have recently been proposed for OB star winds (Crowther et al. 2002; Hillier et al. 2003; Bouret et al. 2003, 2005; Fullerton et al. 2006).”
Probing clumpy stellar winds with a neutron star (2007, background): “There are multiple observational lines of evidence for wind clumping in massive stars from wind line profiles (Bouret et al. 2005; Fullerton et al. 2006), discrete absorption components (Prinja & Howarth 1986), variable line profiles (Lépine & Moffat 1999; Markova et al. 2005), polarimetry (Lupie…”
Mass loss from hot massive stars (2008, methodology): “Fullerton et al (2006) carefully selected a sample of 40 Galactic O-stars, for which also reliableρ2 Ṁ-estimates (Hα , radio) were available, and carried out a detailed comparison between both methods.”
Stellar and wind properties of massive stars in the central parsec of the Galaxy (2006, background): “To name a few, their effective temperatures are lower (Martins et al. 2002; Crowther et al. 2002; Repolust et al. 2004) and their winds are highly clumped (Hillier et al. 2003; Bouret et al. 2005; Fullerton et al. 2006).”
Wind modelling of very massive stars up to 300 solar masses (2011, background): “This has lead to a downward adjustment of empirical mass-loss rates, by factors of up to three (e.g. Mo ﬀ at et al. 1994, Hamann & Koesterke 1998, Mokiem et al. 2007, Puls et al. 2008), and possibly even more (Bouret et al. 2003; Fullerton et al. 2006).”