On the Launching and Structure of Radiatively Driven Winds in Wolf–rayet Stars

Ro, Stephen; Matzner, Christopher D.

doi:10.3847/0004-637x/821/2/109

Cited by 21 publications

(45 citation statements)

References 38 publications

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“…At this location, the energy generation rate reaches a maximum (third panel, dashed line), which is also seen in the density-temperature profiles in Figure 2. As expected from steady-state super-Eddington wind solutions (Nugis & Lamers 2002;Ro & Matzner 2016), the location where the luminosity surpasses the local Eddington rate (second panel) is nearly coincident with the sonic point with respect to the isothermal gas sound speed, k B T /µm p , where µ is the mean molecular weight (top panel).…”

Section: Results and Comparisons To Observationssupporting

confidence: 55%

Wait for It: Post-Supernova Winds Driven by Delayed Radioactive Decays

Shen

Schwab

2017

ApJ

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In most astrophysical situations, the radioactive decay of 56 Ni to 56 Co occurs via electron capture with a fixed half-life of 6.1 days. However, this decay rate is significantly slowed when the nuclei are fully ionized because K-shell electrons are unavailable for capture. In this paper, we explore the effect of these delayed decays on white dwarfs (WDs) that may survive Type Ia and Type Iax supernovae (SNe Ia and SNe Iax). The energy released by the delayed radioactive decays of 56 Ni and 56 Co drives a persistent wind from the surviving WD's surface that contributes to the late-time appearance of these SNe after emission from the bulk of the SN ejecta has faded. We use the stellar evolution code MESA to calculate the hydrodynamical evolution and resulting light curves of these winds. Our post-SN Ia models conflict with late-time observations of SN 2011fe, but uncertainties in our initial conditions prevent us from ruling out the existence of surviving WD donors. Much better agreement with observations is achieved with our post-SN Iax bound remnant models, providing evidence that these explosions are due to deflagrations in accreting WDs that fail to completely unbind the WDs. Future radiative transfer calculations and wind models utilizing explosion simulations for more accurate initial conditions will extend our study of radioactively-powered winds from post-SN surviving WDs and enable their use as powerful discriminants among the various SN Ia and SN Iax progenitor scenarios.

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Section: Results and Comparisons To Observationssupporting

confidence: 55%

Wait for It: Post-Supernova Winds Driven by Delayed Radioactive Decays

Shen

Schwab

2017

ApJ

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“…Cantiello et al 2009;Grassitelli et al 2015;Jiang et al 2015), which would likely be incompatible with a wind launching mechanism at the hot iron bump (e.g. Ro & Matzner 2016). However, the value of 30 km s −1 chosen in this work has only a very limited influence on the location of the critical point.…”

Section: Stellar Atmosphere Modelsmentioning

confidence: 95%

“…that is for example used in stellar structure calculations or wind driving studies based on the grey OPAL opacity tables (e.g. Nugis & Lamers 2002;Ro & Matzner 2016;Gräfener et al 2017;Sanyal et al 2017;Grassitelli et al 2018;Ro 2019). In the deeper layers of the atmosphere where the diffusion approximation is valid, κ F ≈ κ Ross holds as illustrated in Fig.…”

Section: The Radiative Accelerationmentioning

confidence: 99%

Driving classical Wolf-Rayet winds: A Γ- and Z-dependent mass-loss

Sander

Vink

Hamann

2019

Monthly Notices of the Royal Astronomical Society

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Classical Wolf-Rayet (WR) stars are at a crucial evolutionary stage for constraining the fates of massive stars. The feedback of these hot, hydrogen-depleted stars dominates their surrounding by tremendous injections of ionizing radiation and kinetic energy. The strength of a WR wind decides the eventual mass of its remnant, likely a massive black hole. However, despite their major influence and importance for gravitational wave detection statistics, WR winds are particularly poorly understood. In this paper, we introduce the first set of hydrodynamically consistent stellar atmosphere models for classical WR stars of both the carbon (C) and nitrogen (N) sequence, i.e. WC and WN stars, as a function of stellar luminosity-to-mass ratio (or Eddington Gamma), and metallicity. We demonstrate the inapplicability of the CAK wind theory for classical WR stars and confirm earlier findings that their winds are launched at the (hot) iron (Fe) opacity peak. For log Z/Z > −2, Fe is also the main accelerator throughout the wind. Contrasting previous claims of a sharp lower mass-loss limit for WR stars, we obtain a smooth transition to optically thin winds. Furthermore, we find a strong dependence of the mass-loss rates on Eddington Γ, both at solar and sub-solar metallicity. Increases in WC carbon and oxygen abundances turn out to slightly reduce the predicted mass-loss rates. Calculations at subsolar metallicities indicate that below the metallicity of the SMC, WR mass-loss rates decrease much faster than previously assumed, potentially allowing for high black hole masses even in the local universe.

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“…The interplay between these different dynamogenerated magnetic fields could be extremely important for angular momentum transport and internal mixing across massive star envelopes. These local calculations also do not include the possibility of mass loss, which may also change the structures in the iron opacity region (Ro & Matzner 2016). The interplay between convection in this region and winds will be the focus of future global calculations of massive star envelopes.…”

Section: Future Studiesmentioning

confidence: 99%

The Effects of Magnetic Fields on the Dynamics of Radiation Pressure–dominated Massive Star Envelopes

Jiang

Cantiello

Bildsten

et al. 2017

ApJ

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We use three-dimensional radiation magnetohydrodynamic simulations to study the effects of magnetic fields on the energy transport and structure of radiation pressure-dominated main sequence massive star envelopes at the region of the iron opacity peak. We focus on the regime where the local thermal timescale is shorter than the dynamical timescale, corresponding to inefficient convective energy transport. We begin with initially weak magnetic fields relative to the thermal pressure, from 100 to 1000 G in differing geometries. The unstable density inversion amplifies the magnetic field, increasing the magnetic energy density to values close to equipartition with the turbulent kinetic energy density. By providing pressure support, the magnetic field's presence significantly increases the density fluctuations in the turbulent envelope, thereby enhancing the radiative energy transport by allowing photons to diffuse out through low-density regions. Magnetic buoyancy brings small-scale magnetic fields to the photosphere and increases the vertical energy transport, with the energy advection velocity proportional to the Alfvén velocity, although in all cases we study, photon diffusion still dominates the energy transport. The increased radiative and advective energy transport causes the stellar envelope to shrink by several scale heights. We also find larger turbulent velocity fluctuations compared with the purely hydrodynamic case, reaching 100 km s 1 » -at the stellar photosphere. The photosphere also shows vertical oscillations with similar averaged velocities and periods of a few hours. The increased turbulent velocity and oscillations will have strong impacts on the line broadening and periodic signals in massive stars.

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On the Launching and Structure of Radiatively Driven Winds in Wolf–rayet Stars

Cited by 21 publications

References 38 publications

Wait for It: Post-Supernova Winds Driven by Delayed Radioactive Decays

Wait for It: Post-Supernova Winds Driven by Delayed Radioactive Decays

Driving classical Wolf-Rayet winds: A Γ- and Z-dependent mass-loss

The Effects of Magnetic Fields on the Dynamics of Radiation Pressure–dominated Massive Star Envelopes

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