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

Abstract

We present two-dimensional (axisymmetric) neutrino-hydrodynamic simulations of the long-time accretion phase of a 15 M progenitor star after core bounce and before the launch of a supernova explosion, when non-radial hydrodynamic instabilities like convection occur in different regions of the collapsing stellar core and the standing accretion shock instability (SASI) leads to large-amplitude oscillations of the stalled shock with a period of tens of milliseconds. Our simulations were performed with the Prometheus-Vertex code, which includes a multi-flavor, energy-dependent neutrino transport scheme and employs an effective relativistic gravitational potential. Testing the influence of a stiff and a soft equation of state for hot neutron star matter, we find that the non-radial mass motions in the supernova core impose a time variability on the neutrino and gravitational-wave signals with larger amplitudes, as well as higher frequencies in the case of a more compact nascent neutron star. After the prompt shock-breakout burst of electron neutrinos, a more compact accreting remnant produces higher neutrino luminosities and higher mean neutrino energies. The observable neutrino emission in the SASI sloshing direction exhibits a modulation of several ten percent in the luminosities and around 1 MeV in the mean energies with most power at typical SASI frequencies between roughly 20 and 100 Hz. The modulation is caused by quasi-periodic variations in the mass accretion rate of the neutron star in each hemisphere. At times later than ∼50-100 ms after bounce, the gravitational-wave amplitude is dominated by the growing low-frequency ( < ∼ 200 Hz) signal associated with anisotropic neutrino emission. A high-frequency wave signal results from nonradial gas flows in the outer layers of the anisotropically accreting neutron star. Right after bounce such nonradial mass motions occur due to prompt post-shock convection in both considered cases and contribute mostly to the early wave production around 100 Hz. Later they are instigated by the SASI and by convective overturn that vigorously stir the neutrino-heating and cooling layers, and also by convective activity developing below the neutrinosphere. The gravitational-wave power then peaks at about 300-800 Hz, connected to changes in the mass quadrupole moment on a timescale of milliseconds. Distinctively higher spectral frequencies originate from the more compact and more rapidly contracting neutron star. Both the neutrino and gravitational-wave emission therefore carry information that is characteristic of the properties of the nuclear equation of state in the hot remnant. The detectability of the SASI effects in the neutrino and gravitational-wave signals is briefly discussed.

The next-generation liquid-scintillator neutrino observatory LENA

“…Many existing and near-future detectors will pick up tens to hundreds of events [72,73], whereas statistics comparable to LENA is provided only by Super-Kamiokande. Moreover, the high-energy neutrino telescope IceCube at the South Pole will register roughly 10 6 uncorrelated Cherenkov photons in excess of background, providing superior sensitivity to fast signal variations that are suggested by recent multi-dimensional simulations [74][75][76].…”

“…16, middle) depends on the mass infall rate and thus on the progenitor-dependent structure of the stellar core, with more massive cores producing higher luminosities [108,109]. Luminosity variations during this phase [74][75][76], accompanied by sizable gravitational-wave emission at several hundred Hz [74,110] would confirm the presence of violent hydrodynamic instabilities stirring the accretion flow around the assembling neutron star. Such activity and a several hundred millisecond delay of the onset of the explosion are expected within the framework of the delayed neutrino-driven mechanism.…”

IceCube sensitivity for low-energy neutrinos from nearby supernovae

“…They are the only examples so far where one-dimensional simulations obtain neutrino-powered supernova explosions and two-dimensional simulations yield only minor dynamical and energetic modifcations. In Table 4 we also refer to a two-dimensional axisymmetric simulation by Marek et al (2009) of a 15 M progenitor star that covers 0.38 s following the collapse. Results with full multi-angle neutrino transport in two dimensions have been reported by Brandt et al (2011).…”

“…Reference Progenitor #ν's #ν's mass (M ) t < 380 ms all times "Livermore" (Totani et al 1997) 2 0 0 .174 × 10 6 0.79 × 10 6 "Garching LS-EOS 1d" (Kitaura et al 2006) 8 −10 0.069 × 10 6 -"Garching WH-EOS 1d" (Kitaura et al 2006) 8 −10 0.078 × 10 6 -"Garching SASI 2d" (Marek et al 2009) 1 5 0 .106 × 10 6 -"1987A at 10 kpc" (Pagliaroli et al 2009b) 15−20 (0.57 ± 0.18) × 10 6 "O-Ne-Mg 1d" (Hüdepohl et al 2010) 8 . 8 0 .054 × 10 6 0.17 × 10 6 "Quark Star (full opacities)" (Dasgupta et al 2010) 1 0 0 .067 × 10 6 -"Black Hole LS-EOS" (Sumiyoshi et al 2007) 4 0 0 .395 × 10 6 1.03 × 10 6 "Black Hole SH-EOS" (Sumiyoshi et al 2007) 4 0 0 .335 × 10 6 3.40 × 10 6…”

Correlated gravitational wave and neutrino signals from general-relativistic rapidly rotating iron core collapse

“…Both are emitted inside the core where the deciding dynamics occur and travel to observers on Earth essentially unimpeded by intervening material. Neutrinos carry primarily thermodynamic and structural information about their source (e.g., [24][25][26][27]) while gravitational waves (GWs), owing to their quadrupole nature, provide complementing information on the multidimensional dynamics of the core (e.g., [24,[28][29][30][31]). The combined observation of neutrinos and GWs from the next nearby core collapse event may place stringent constraints on rotation in the core in particular and on corecollapse supernova physics in general (see, e.g., [24,[32][33][34] and references therein).…”