The wind properties of O-type stars at sub-SMC metallicity

Abstract

Radiation-driven winds heavily influence the evolution and fate of massive stars. Feedback processes from these winds impact the properties of the interstellar medium of their host galaxies. The dependence of mass loss on stellar properties is poorly understood, particularly at low metallicity ($Z$). We aim to characterise stellar and wind properties of massive stars in Local Group dwarf galaxies with $Z$ below that of the Small Magellanic Cloud and confront our findings to theories of radiation-driven winds. We perform quantitative optical and UV spectroscopy on a sample of 11 O-type stars in nearby dwarf galaxies with $Z<0.2Z_{\odot }$. The stellar atmosphere code Fastwind and the genetic algorithm Kiwi-GA are used to determine stellar and wind parameters. Inhomogeneities in the wind are assumed to be optically thin. The winds of the sample stars are weak, with mass loss rates $\sim 10^{-9}-10^{-7}{M}_{\odot }{\mathrm{yr}}^{-1}$. Such feeble winds can only be constrained if UV spectra are available. The modified wind momentum as a function of luminosity ($L$) for stars in this $Z$ regime is in agreement with extrapolations to lower $Z$ of a recently established empirical relation for this quantity as a function of both $L$ and $Z$. However, theoretical prescriptions do not match our results or those of other recent analyses at low luminosity ($L\lesssim 10^{5.2}{L}_{\odot }$) and low $Z$; in this regime, they predict winds that are stronger by an order of magnitude or more. For our sample stars at $Z\sim 0.14Z_{\odot }$, with masses $\sim 30-50M_{\odot }$, stellar winds strip little mass during main-sequence evolution. However, if the steep dependence of mass loss on luminosity found here also holds for more massive stars at these metallicities, these may suffer as severely from main-sequence mass stripping as very massive stars in the Large Magellanic Cloud and Milky Way.

Accepted for publication in A&A, 26 pages, 16 figures, 16 tables, Appendices G and H online at Zenodo

References in corpus (36)

• Cosmic Star Formation History
• Binary interaction dominates the evolution of massive stars
• Mass loss from hot massive stars
• The ACS Nearby Galaxy Survey Treasury
• UBVJHK synthetic photometry of Galactic O stars
• The empirical metallicity dependence of the mass-loss rate of O- and early B-type stars
• The Supernova Channel of Super-AGB Stars
• The evolution of rotating very massive stars with LMC composition
• 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
• Million-Degree Plasma Pervading the Extended Orion Nebula
• A Detailed Study of Feedback from a Massive Star
• Testing massive star evolution, star-formation history and feedback at low metallicity : Spectroscopic analysis of OB stars in the SMC Wing
• Theory and Diagnostics of Hot Star Mass Loss
• VLT spectroscopy of blue supergiants in IC 1613
• Metallicity-dependent wind parameter predictions for OB stars
• The Araucaria Project. VLT spectra of blue supergiants in WLM: classification and first abundances
• A consistent solution for the velocity field and mass-loss rate of massive stars
• Winds of low-metallicity OB-type stars: HST-COS spectroscopy in IC1613
• No breakdown of the radiatively-driven wind theory in low-metallicity environments
• The Araucaria Project: Distance to the Local Group Galaxy NGC 3109 from Near-Infrared Photometry of Cepheids
• The properties of ten O-type stars in the low-metallicity galaxies IC 1613, WLM and NGC 3109
• Empirical mass-loss rates and clumping properties of Galactic early-type O supergiants
• Very Massive Stars and Pair-Instability Supernovae: Mass-loss Framework for low Metallicity
• X-Shooting ULLYSES: Massive stars at low metallicity. III. Terminal wind speeds of ULLYSES massive stars
• Stellar wind properties of the nearly complete sample of O stars in the low metallicity young star cluster NGC346 in the SMC galaxy
• X-ray properties of early-type stars in the Tarantula Nebula from T-ReX
• The earliest O-type eclipsing binary in the Small Magellanic Cloud, AzV 476: A comprehensive analysis reveals surprisingly low stellar masses
• The Ionizing Spectra of Extremely Metal-Poor O Stars: Constraints from the Only HII Region in Leo P
• X-Shooting ULLYSES: Massive Stars at low metallicity VIII. Stellar and wind parameters of newly revealed stripped stars in Be binaries
• A new reference catalogue for the very metal-poor Universe: +150 OB stars in Sextans A
• Wind properties of Milky Way and SMC massive stars: empirical Z dependence from CMFGEN models
• X-Shooting ULLYSES: Massive Stars at low metallicity II. DR1: Advanced optical data products for the Magellanic Clouds
• Empirical mass-loss rates and clumping properties of O-type stars in the LMC
• X-Shooting ULLYSES: massive stars at low metallicity: XII. The clumped winds of O-type (super)giants in the Large Magellanic Cloud
• Effect of rotational mixing and metallicity on the hot star wind mass-loss rates

Cited by in corpus (2)

• X-Shooting ULLYSES: massive stars at low metallicity: XII. The clumped winds of O-type (super)giants in the Large Magellanic Cloud
• The Treasury of Extremely Metal-Poor O Stars