The empirical metallicity dependence of the mass-loss rate of O- and early B-type stars

By M. R. Mokiem, A. D. Koter, J. Vink, J. Puls, Christopher H. Evans, S. Smartt, P. Crowther, A. Herrero, N. Langer, D. Lennon and 2 more. 2007

246 citations recorded by the source corpus.

We present a comprehensive study of the observational dependence of the mass-loss rate in stationary stellar winds of hot massive stars on the metal content of their atmospheres. The metal content of stars in the Magellanic Clouds is discussed, and a critical assessment is given of state-of-the-art mass-loss determinations of OB stars in these two satellite systems and the Milky-Way. Assuming a powerlaw dependence of mass loss on metal content, u M ∝ Z m , and adopting a theoretical relation between the terminal flow velocity and metal content, v∞ ∝ Z 0.13 (Leitherer et al. 1992, ApJ, 401, 596), we find m = 0.83 ± 0.16 for non-clumped outflows from an analysis of the wind momentum luminosity relation (WLR) for stars more luminous than 10 5.2 L� . Within the errors, this result is in agreement with the prediction m = 0.69 ± 0.10 by Vink et al. (2001, A&A, 369, 574). Absolute empirical values for the mass loss, based on Hα and ultraviolet (UV) wind lines, are found to be a factor of two higher than predictions in this high luminosity regime. If this difference is attributed to inhomogeneities in the wind, and this clumping does not impact the predictions, this would imply that luminous O and early-B stars have clumping factors in their Hα and UV line forming regions of about a factor of four. For lower luminosity stars, the winds are so weak that their strengths can generally no longer be derived from optical spectral lines (essentially Hα) and one must currently rely on the analysis of UV lines. We confirm that in this low-luminosity domain the observed Galactic WLR is found to be much steeper than expected from theory (although the specific sample is rather small), leading to a discrepancy between UV mass-loss rates and the predictions by a factor 100 at luminosities of L ∼ 10 4.75 L� , the origin of which is unknown. We emphasize that even if the current mass-loss rates of hot luminous stars would turn out to be overestimated as a result of wind clumping, but the degree of clumping would be rather independent of metallicity, the scalings derived in this study are expected to remain correct.

Subfields: Astronomy and Astrophysics, Education, Instrumentation

View Paper: https://www.semanticscholar.org/paper/d05301ee43b1279a7539b807deca34374a1d9959

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Citations in the corpus

Mass Loss: Its Effect on the Evolution and Fate of High-Mass Stars (2014, background): “Thus, the rate at which mass is lifted from the star by this 6 Smith mechanism depends on the UV luminosity of the star, the temperature (and ionization), and the metallicity, Z (Mokiem et al. 2007, Puls et al. 2008).”
THE ROTATION RATES OF MASSIVE STARS: THE ROLE OF BINARY INTERACTION THROUGH TIDES, MASS TRANSFER, AND MERGERS (2012, background): “The winds of massive main-sequence stars, which are fairly well understood (Kudritzki & Puls 2000; Mokiem et al. 2007), are stronger at higher mass and metallicity (Vink et al. 2001) and for more rapid rotation (Friend & Abbott 1986).”
Mass loss from hot massive stars (2008, methodology): “From the analysis of the SMC/LMC objects by Mokiem et al (2006) and Mokiem et al (2007a), respectively, and in combination with data from previous investiga ions, Mokiem et al (2007b) derived the WLRs for Galactic, LMC and SMC objects, with rather narrow 1-σ confidence intervals, and showed that…”
The SILCC project - III. Regulation of star formation and outflows by stellar winds and supernovae (2016, background): “…metallicity stars have, during most of their evolution, winds with lower mass-loss rates (e.g. Kudritzki, Pauldrach & Puls 1987; Vink, de Koter & Lamers 2001; Krtička 2006; Mokiem et al. 2007; Gräfener & Hamann 2008) and somewhat lower terminal velocities (Leitherer et al. 1992; Krtička 2006).”
Scaled solar tracks and isochrones in a large region of the Z-Y plane. II. From 2.5 to 20 solar masses (2009, background): “A comparison between mass loss prescriptions and observed mass loss rates, and the observational dependence of the rate on the metal content of massive stars atmospheres was presented by Mokiem et al. (2007).”
A new route towards merging massive black holes (2016, background): “Because the winds are metallicity dependent (Mokiem et al. 2007; Vink & de Koter 2005), metal-rich systems are found to widen strongly, which limits the tidal interaction so that the homogeneous evolution may end.”
The chemically homogeneous evolutionary channel for binary black hole mergers: rates and properties of gravitational-wave events detectable by advanced LIGO (2016, background): “The reduction of stellar wind mass loss at low metallicity (Vink et al. 2001; Mokiem et al. 2007) leads to a preference for the progenitors to form at higher redshift or in dwarf galaxies.”
The SEDs and host galaxies of the dustiest GRB afterglows (2011, background): “…to explode as a GRB (Woosley 1993; MacFadyen & Woosley 1999), as they would in principle be able to retain a larger amount of angular momentum at the time of stellar collapse because of the lower wind pressures and losses throughout their evolution (e.g., Yoon & Langer 2005; Mokiem et al. 2007).”
The VLT-FLAMES Tarantula Survey XXVII. Physical parameters of B-type main-sequence binary systems in the Tarantula nebula (2017, unknown): “Additionally, mass loss can be signiﬁcant, particularly for more luminous stars and in metal-rich environments (Puls et al. 2008; Mokiem et al. 2007) and this can e ﬀ ect their evolution (Chiosi & Maeder 1986).”
PARSEC evolutionary tracks of massive stars up to 350 M ☉ at metallicities 0.0001 ≤ Z ≤ 0.04 (2015, background): “…of massive stars in near solar environments, it is used independently from the metallicity of the galaxy, in spite of the fact that the mass-loss rates themselves do depend on the abundance of heavy elements (Kudritzki & Puls 2000; Puls, Springmann & Lennon 2000; Mokiem et al. 2007; Smith 2014).”
Classical Be stars (2013, background): “Indeed, the radiatively driven stellar winds in OB stars are found to be weaker in the SMC (Bouret et al. 2003), and a comparative study of the MW, LMC, and SMC has found a gradient of mass loss with metallicity (Mokiem et al. 2007).”
A LIBRARY OF THEORETICAL ULTRAVIOLET SPECTRA OF MASSIVE, HOT STARS FOR EVOLUTIONARY SYNTHESIS (2010, background): “Lines from CNO elements take over only if Teff ≈ 40,000 K (Mokiem et al. 2007).”
Merging binary black holes formed through chemically homogeneous evolution in short-period stellar binaries (2015, background): “0.004, the radiatively driven winds are strongly reduced as predicted by Vink et al. (2000, 2001) and empirically verified by Mokiem et al. (2007).”
Supernova remnants: the X-ray perspective (2011, unknown): “For example, a massive O-star will spend ∼ 90% of its life on the main sequence, during which it blows a fast, tenuous wind with velocity vw ≈ 1500− 3000 km s−1, with Ṁ ≈ 5×10−7−10−5 M⊙ yr−1 (e.g. Mokiem et al., 2007).”
Formation of Double Neutron Star Systems (2017, unknown): “2006; Mokiem et al. 2007; Markova & Puls 2008; Langer 2012; Šurlan et al. 2013; Chaty 2013; Falanga et al. 2015).”