Mass-loss predictions for O and B stars as a function of metallicity

Abstract

Abstract.We have calculated a grid of massive star wind models and mass-loss rates for a wide range of metal abundances between 1/100 ≤ Z/Z ≤ 10. The calculation of this grid completes the Vink et al. (2000) for stars with T eff > ∼ 25 000 K, andṀ ∝ Z 0.64 for B supergiants with T eff < ∼ 25 000 K. Although it is derived that the exponent of the mass loss vs. metallicity dependence is constant over a large range in Z, one should be aware of the presence of bi-stability jumps at specific temperatures. Here the character of the line driving changes drastically due to recombinations of dominant metal species resulting in jumps in the mass loss. We have investigated the physical origins of these jumps and have derived formulae that combine mass loss recipes for both sides of such jumps. As observations of different galaxies show that the ratio Fe/O varies with metallicity, we make a distinction between the metal abundance Z derived on the basis of iron or oxygen lines. Our mass-loss predictions are successful in explaining the observed mass-loss rates for Galactic and Small Magellanic Cloud Otype stars, as well as in predicting the observed Galactic bi-stability jump. Hence, we believe that our predictions are reliable and suggest that our mass-loss recipe be used in future evolutionary calculations of massive stars at different metal abundance. A computer routine to calculate mass loss is publicly available.

Supernovae from Massive Stars

“…In the more massive solar metallicity models it ranges typically between 10 −6 and 10 −5 M ⊙ /yr [14,15]. This value is high enough to induce a substantial reduction of the total mass of the star and hence to expose to the surface the zones partially modified by the core H burning.…”

On the formation of galactic black hole low-mass X-ray binaries

“…Here, we adopt two prescriptions for the wind loss rate. The first one is taken from Hurley et al (2000) and Vink (2001) for O and B stars in different stages, denoted as Wind1 hereafter, while the other one, denoted as Wind2, adopts the maximum value of the prescriptions above in all the evolutionary stages, to be consistent with Xu & Li (2010a,b), and to set an upper limit for the influence of the stellar wind. The effect of stellar rotation is ignored, because in our calculation for LMXB formation, CE evolution usually occurs during Case C mass transfer when the primary star has evolved to be a supergiant star with very slow rotation due to stellar evolution and/or tidal synchronization.…”

Nonthermal particles and photons in starburst regions and superbubbles

“…The models of stellar evolution by Chiosi and Maeder (1986), Maeder and Meynet (1988), Lamers and Cassinelli (1999) predict that such a star would eject into the interstellar medium about 29 M of hydrogen, ∼ 8 M of He, and ∼ 1 M of C and O (almost 38 M of gas in total). A very useful recipe to estimate the mass-loss rate as a function of the stellar mass and luminosity, effective temperature and terminal velocity of the wind for different metal abundances can be found in Vink et al (2000Vink et al ( , 2001. Magnetic fields in OBstars are thought to be at the level of ∼ 100 G. They play a role in the structure and evolution of young massive stars maintaining a rotation law to be close to uniformity (see, e.g., Maeder et al 2009).…”