Gravitational Radiation from Standing Accretion Shock Instability in Core‐Collapse Supernovae

Abstract

We present the results of numerical experiments, in which we study how the asphericities induced by the growth of the standing accretion shock instability (SASI) produce the gravitational waveforms in the postbounce phase of corecollapse supernovae. To obtain the neutrino-driven explosions, we parameterize the neutrino fluxes emitted from the central protoneutron star and approximate the neutrino transfer by a light-bulb scheme. We find that the waveforms due to the anisotropic neutrino emissions show the monotonic increase with time, whose amplitudes are up to two order-of-magnitudes larger than the ones from the convective matter motions outside the protoneutron stars. We point out that the amplitudes begin to become larger when the growth of the SASI enters the nonlinear phase, in which the deformation of the shocks and the neutrino anisotropy become large. From the spectrum analysis of the waveforms, we find that the amplitudes from the neutrinos are dominant over the ones from the matter motions at the frequency below ∼ 100 Hz, which are suggested to be within the detection limits of the detectors in the next generation such as LCGT and the advanced LIGO for a supernova at 10 kpc. As a contribution to the gravitational wave background, we show that the amplitudes from this source could be larger at the frequency above ∼ 1 Hz than the primordial gravitational wave backgrounds, but unfortunately, invisible to the proposed space-based detectors.

Equation-of-state dependent features in shock-oscillation modulated neutrino and gravitational-wave signals from supernovae

“…This function becomes negative in the equatorial belt between 60 • and 120 • , see Fig. 1 of Kotake et al (2007).…”

“…(27) of Müller & Janka (1997). For the case of an axially symmetric source, Kotake et al (2007) derived a compact expression (see their Eq. (8) and note that our Ψ, following the notation of Müller & Janka 1997, is their Φ), which is visualized as a function of the polar angle θ in their Fig.…”

“…They explained their finding by the particular properties of the SASI and the corresponding post-shock accretion flow in models that are constrained by the assumption of axial symmetry. In this case the SASI oscillations must occur along the polar grid axis, and Kotake et al (2007) argued that the influence of this on the accretion flow makes the neutrino emission biased towards the regions around the symmetry axis (see also Sect. 3.2), thus leading to positive and growing wave amplitudes.…”

“…Why do we come to different conclusions about the neutrino emission asymmetry than Kotake et al (2007) ν e production in the accretion layer? In the first place one must note that the modeling approach taken by Kotake et al (2007) is fundamentally different from ours.…”

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). …”