The Evolution of Supernovae in Circumstellar Wind Bubbles. II. Case of a Wolf‐Rayet Star

Abstract

Mass-loss from massive stars leads to the formation of circumstellar windblown bubbles surrounding the star, bordered by a dense shell. When the star ends its life in a supernova (SN) explosion, the resulting shock wave will interact with this modified medium. In a previous paper (Dwarkadas 2005) we discussed the basic parameters of this interaction with idealized models. In this paper we go a step further and study the evolution of SNe in the wind blown bubble formed by a 35 M ⊙ star that starts off as an O star, goes through a red supergiant phase, and ends its life as a Wolf-Rayet star. We model the evolution of the circumstellar medium throughout its lifetime, and then the expansion of the SN shock wave within this medium. Our simulations clearly reveal fluctuations in density and pressure within the surrounding medium, due to the changing massloss parameters over the star's evolution. The SN shock interacting with these fluctuations, and then with the dense shell surrounding the wind-blown cavity, gives rise to a variety of transmitted and reflected shocks in the wind bubble. The interactions between these various shocks and discontinuities is examined, and its effects on the emission from the remnant, especially in the X-ray regime, is noted. In this particular case the shock wave is trapped in the dense shell for a large number of doubling times, and the remnant size is restricted by the size of the surrounding circumstellar bubble. Our multi-dimensional simulations reveal the presence of several hydrodynamic instabilities. They show that the turbulent interior, coupled with the large fluctuations in density and pressure, gives rise to an extremely corrugated SN shock wave. The shock shows considerable wrinkles as it impacts the dense shell, and the impact occurs in a piecemeal fashion, with some parts of the shock wave interacting with the shell before the others. As each interaction is accompanied by an increase in the X-ray and optical emission, different parts of the shell will 'light-up' at different times. The reflected shock

THE COLLIMATION AND ENERGETICS OF THE BRIGHTESTSWIFTGAMMA-RAY BURSTS

“…A variety of recent results, ranging from the discovery of fast-moving (v ≈ 6000 km s −1 ) material ejected from η Car (Smith 2008), to the dense circumstellar material partially powering the luminous (M V ≈ −22 mag) SN 2006gy (Ofek et al 2007;Smith et al 2007), to detection of a pre-SN outburst from SN 2006jc (Pastorello et al 2007;Foley et al 2007) and SN 2005gl (Gal-Yam & Leonard 2009, suggest that massive stars undergo violent periods of episodic mass loss in the late stages of stellar evolution. Future theoretical progress to pin down the expected density profile surrounding massive stars in the latest stages of stellar evolution at distances relevant to GRB afterglows (∼1 pc) (e.g., Ramirez-Ruiz et al 2005;Dwarkadas 2007), or alternatively, to more reliably infer the density profile from afterglow observations (e.g., van Eerten & Wijers 2009), might help to resolve this discrepancy An additional concern, motivated by the double-jet models for GRB 030329 (Berger et al 2003b;van der Horst et al 2005) and GRB 080319B , is our assumption that the entire relativistic outflow is collimated into a uniform jet with a single opening angle (the so-called top-hat model). A variety of other models for structured jets have been proposed, typically with the Lorentz factor of the outflow varying as a function of angle from the jet axis (see, e.g., Granot 2007 for a review).…”

Acceleration of cosmic rays by young core-collapse supernova remnants

“…The mass-loss rates of WR stars are somewhat lower than those of RSG winds, but their wind velocities are more than two orders of magnitude higher, leading to wind densities that are more than two orders of magnitude lower. The high momentum of the winds pushes outward on the RSG shell, breaking it up in the process and mixing the RSG material into the WR wind (Dwarkadas 2007;Toalá & Arthur 2011;Dwarkadas & Rosenberg 2013). This mixed material approaches, and could bounce back from, the main-sequence shell.…”

Asymmetric supernova remnants generated by Galactic, massive runaway stars

“…They therefore exc 0000 RAS hibit a wide range of morphologies that can be used to constrain their progenitors and/or ambient medium properties. The distribution of circumstellar matter depends on the progenitor properties (Bedogni & D'Ercole 1988;Ciotti & D'Ercole 1989;Dwarkadas 2005Dwarkadas , 2007 and the presence of ISM structures, e.g. borders of neighbouring diffuse nebulae or filaments that affect the propagation of the supernova ejecta.…”