Super-Eddington stellar winds driven by near-surface energy deposition

Abstract

We develop analytic and numerical models of the properties of super-Eddington stellar winds, motivated by phases in stellar evolution when super-Eddington energy deposition (via, e.g., unstable fusion, wave heating, or a binary companion) heats a region near the stellar surface. This appears to occur in luminous blue variables (LBVs), Type IIn supernovae progenitors, classical novae, and X-ray bursts. We show that when the wind kinetic power exceeds Eddington, the photons are trapped and behave like a fluid. Convection does not play a significant role in the wind energy transport. The wind properties depend on the ratio of a characteristic speed in the problem v crit ∼ (ĖG) 1/5 (whereĖ is the heating rate) to the stellar escape speed near the heating region v esc (r h ). For v crit v esc (r h ) the wind kinetic power at large radiiĖ w ∼Ė. For v crit v esc (r h ), most of the energy is used to unbind the wind material and thusĖ w Ė . Multidimensional hydrodynamic simulations without radiation diffusion using FLASH and one-dimensional hydrodynamic simulations with radiation diffusion using MESA are in good agreement with the analytic predictions. The photon luminosity from the wind is itself superEddington but in many cases the photon luminosity is likely dominated by 'internal shocks' in the wind. We discuss the application of our models to eruptive mass loss from massive stars and argue that the wind models described here can account for the broad properties of LBV outflows and the enhanced mass loss in the years prior to Type IIn core-collapse supernovae.

Unifying Type II Supernova Light Curves with Dense Circumstellar Material

“…A better measurement of the extent of the CSM along with its velocity may help to better connect its properties with various stages of stellar burning. This will assist in identifying its physical origin (see discussions in Smith & Arnett 2014;Woosley & Heger 2015;Quataert et al 2016, and references therein).…”

Dawes Review 6: The Impact of Companions on Stellar Evolution

“…Multidimensional simulations able to model accurately both the stars and the interaction are currently impossible because of the challenge in modelling simultaneously a large range of space and timescales. However, great progress over recent years has been made in 3D hydrodynamics with 3D models of individual stars (e.g., Chiavassa et al 2011, where important relevant physics is captured) and numerical techniques being refined and developed to be adopted for binary modelling (e.g., Ohlmann et al, 2016a;Quataert et al, 2016). These studies are part of a revival in the field of stellar astrophysics, the start of which may be observed in the increase by over a factor of 10 in citations to seminal binary interaction papers such as that of Webbink (1984, Figure 1), well above the factor of 2.3 increase in the overall volume of astrophysics papers that has been witnessed between 1985 and 2015. This review is arranged as follows.…”

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

“…Once our initial models are constructed, we turn on MESA's hydrodynamic capabilities. We also make use of recently implemented outer boundary conditions that were developed for modeling super-Eddington stellar winds (Quataert et al 2016). These allow us to set the optical depth at the outer boundary to be τ = 10 −4 × 2/3, so that we can follow the wind out to arbi-trarily large distances.…”