2019MNRAS.485..988O

Motivated by the eruptive mass-loss inferred from Luminous Blue Variable (LBV) stars, we present 1D hydrodynamical simulations of the response from sudden energy injection into the interior of a very massive (100 M_☉) star. For a fiducial case with total energy addition set to a factor f = 0.5 of the net stellar binding energy, and applied within the stellar envelope, we detail the dynamical response that leads to ejection of the outermost 7.2 M_☉. We find that the ejecta's variations in time t and radius r for the velocity v, density ρ, and temperature T are quite well fit by similarity forms in the variable r/t ≃ v. Specifically the scaled density follows a simple exponential decline ρt³ ∼ exp (- r/v_ot). This 'exponential similarity' leads to analytic scaling relations for total ejecta mass ΔM and kinetic energy ΔK that agree well with the hydrodynamical simulations, with the specific-energy-averaged speed related to the exponential scale speed v_o through {bar}v ≡sqrt(2)ΔK/ΔM = sqrt(12) v_ o_, and a value comparable to the star's surface escape speed, v_esc. Models with energy added in the core develop a surface shock breakout that propels an initial, higher speed ejecta (>5000 km s^–1), but the bulk of the ejected material still follows the same exponential similarity scalings with {bar}v ~v_ esc_. A broader parameter study examines how the ejected mass and energy depends on the energy-addition factor f, for three distinct model series that locate the added energy in either the core, envelope, or near-surface. We conclude by discussing the relevance of these results for understanding LBV outbursts and other eruptive phenomena, such as failed supernovae and pulsational pair instability events.