Metallicity-dependent wind parameter predictions for OB stars

Abstract

Mass-loss rates and terminal wind velocities are key parameters that determine the kinetic wind energy and momenta of massive stars. Furthermore, accurate mass-loss rates determine the mass and rotational velocity evolution of mass stars, and their fates as neutron stars and black holes in function of metallicity (Z). Here we update our Monte Carlo mass-loss Recipe with new dynamically-consistent computations of the terminal wind velocity -- as a function of Z. These predictions are particularly timely as the HST ULLYSES project will observe ultraviolet spectra with blue-shifted P Cygni lines of hundreds of massive stars in the low-Z Large and Small Magellanic Clouds, as well as sub-SMC metallicity hosts. Around 35 000 K, we uncover a weak-wind "dip" and we present diagnostics to investigate its physics with ULLYSES and X-Shooter data. We discuss how the dip may provide important information on wind-driving physics, and how this is of key relevance towards finding a new gold-standard for OB star mass-loss rates. For B supergiants below the Fe IV to III bi-stability jump, the terminal velocity is found to be independent of Z and M, while the mass-loss rate still varies as $\dot{M}\propto Z^{0.85}$. For O-type stars above the bi-stability jump we find a terminal-velocity dependence of $v_{\infty }\propto Z^{0.19}$ and the Z-dependence of the mass-loss rate is found to be as shallow as $\dot{M}\propto Z^{0.42}$, implying that to reproduce the `heavy' black holes from LIGO/VIRGO, the `low Z' requirement becomes even more stringent than was previously anticipated.

MNRAS Accepted. 12 pages, 13 figures. Notes on IDL/Python Mass-loss Recipe Usage added to the Appendix

References in corpus (24)

• GW190521: A Binary Black Hole Merger with a Total Mass of $150M_{\odot }$
• Pre-Supernova Evolution of Massive Single and Binary Stars
• Mass loss from hot massive stars
• The empirical metallicity dependence of the mass-loss rate of O- and early B-type stars
• 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 Tarantula Survey XVII. Physical and wind properties of massive stars at the top of the main sequence
• On the consistent treatment of the quasi-hydrostatic layers in hot star atmospheres
• Implications of the metallicity dependence of Wolf-Rayet winds
• VLT spectroscopy of blue supergiants in IC 1613
• A consistent solution for the velocity field and mass-loss rate of massive stars
• Very Massive Stars in the Local Universe
• Driving classical Wolf-Rayet winds: A Γ- and Z-dependent mass-loss
• 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
• Rotating massive O stars with non-spherical 2D winds
• Winds of low-metallicity OB-type stars: HST-COS spectroscopy in IC1613
• No breakdown of the radiatively-driven wind theory in low-metallicity environments
• Wind-envelope interaction as the origin of the slow cyclic brightness variations of luminous blue variables
• The properties of ten O-type stars in the low-metallicity galaxies IC 1613, WLM and NGC 3109
• Testing the predicted mass-loss bi-stability jump at radio wavelengths
• Instabilities in the Envelopes and Winds of Very Massive Stars
• On the H$\alpha$ Behaviour of Blue Supergiants: Rise and Fall over the Bi-stability Jump
• CMF models of hot star winds II. Reduction of O star wind mass-loss rates in global models
• Stellar population of the superbubble N206 in the LMC I. Analysis of the Of-type stars