A New Mechanism for Core‐Collapse Supernova Explosions

Abstract

In this paper, we present a new mechanism for core-collapse supernova explosions that relies upon acoustic power generated in the inner core as the driver. In our simulation using an 11-M ⊙ progenitor, an advective-acoustic oscillationà la Foglizzo with a period of ∼25−30 milliseconds (ms) arises ∼200 ms after bounce. Its growth saturates due to the generation of secondary shocks, and kinks in the resulting shock structure funnel and regulate subsequent accretion onto the inner core. However, this instability is not the primary agent of explosion. Rather, it is the acoustic power generated early on in the inner turbulent region stirred by the accretion plumes, and most importantly, but later on, by the excitation and sonic damping of core g-mode oscillations. An ℓ = 1 mode with a period of ∼3 ms grows at late times to be prominent around ∼500 ms after bounce. The accreting protoneutron star is a self-excited oscillator, "tuned" to the most easily excited core g-mode. The associated acoustic power seen in our 11-M ⊙ simulation is sufficient to drive the explosion >550 milliseconds after bounce. The angular distribution of the emitted sound is fundamentally aspherical. The sound pulses radiated from the core steepen into shock waves that merge as they propagate into the outer mantle and deposit their energy and momentum with high efficiency. The ultimate source of the acoustic power is the gravitational energy of infall and the core oscillation acts like a transducer to convert this accretion energy into sound. An advantage of the acoustic mechanism is that acoustic power does not abate until accretion subsides, so that it is available as long as it may be needed to explode the star. This suggests a natural means by which the supernova is self-regulating.

Stellar Forensics with the Supernova‐GRB Connection

“…This result that asphericites are an ubiquitous feature during core-collapse is in line with similar conclusions based on polarization studies of SN II, Ib and SN Ic e.g., (Leonard & Filippenko 2005;Maund et al 2009a), neutron-star kick velocities (Wang et al 2006), young SN remnant morphologies (Fesen et al 2006), and theoretical modeling efforts (Scheck et al 2006;Burrows et al 2006;Dessart et al 2008). Aspherical explosion geometry does not appear to be distinguishing feature of SN-GRBs, though SN-GRBs may have the highest degree of asphericity according to some models (Maeda et al 2008).…”

Crucial Physical Dependencies of the Core-Collapse Supernova Mechanism

“…A comprehensive set of neutrino-matter interactions are followed in FORNAX, and these are described in Burrows et al (2006aBurrows et al ( , 2006b. Inelastic neutrino-nucleon scattering is handled using a modified version of the Thompson et al (2003) approach (Sect.…”

“…The detailed theory of the structure functions and redistribution kernels for such inelastic scattering, including the effects of final-state blocking and the thermal spectrum of the targets, can be found in Burrows et al (2006aBurrows et al ( , 2006b), Reddy et al (1999), Thompson et al (2003), and Thompson et al (2000). Pioneering work on inelastic scattering off electrons in the core-collapse context can be found in Bruenn (1985) and Mezzacappa and Bruenn (1993).…”

“…The calculations of Burrows et al (2006aBurrows et al ( , 2006bBurrows et al ( , 2007a and Ott et al (2008), using the VULCAN/2D code, and Dolence et al (2015), using the CASTRO code (Zhang et al 2011(Zhang et al , 2013 employed multi-dimensional transport, and not ray-by-ray+, but in neither of these 2D studies did the authors see explosions by the neutrino mechanism. VULCAN/2D did not have all the terms to order v/c in the transport, but CASTRO did, and the results were similar (Dolence et al 2015).…”

Menus for Feeding Black Holes

“…The physical reason for this instability is the advective-acoustic cycle (Foglizzo 2002;Foglizzo et al 2005;Guilet and Foglizzo 2012): entropy/vorticity perturbations are generated at the shock and advected to the sonic point, where an acoustic wave is excited and propagated back to the shock, leading to the growth of the entropy/vorticity perturbation. SASI helps drive supernova explosions (Burrows et al 2006) and causes the emission of gravitational waves (Kotake et al 2007). …”