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

Abstract

We present results from a new set of 3D general-relativistic hydrodynamic simulations of rotating iron core collapse. We assume octant symmetry and focus on axisymmetric collapse, bounce, the early postbounce evolution, and the associated gravitational wave (GW) and neutrino signals. We employ a finite-temperature nuclear equation of state, parameterized electron capture in the collapse phase, and a multi-species neutrino leakage scheme after bounce. The latter captures the important effects of deleptonization, neutrino cooling and heating and enables approximate predictions for the neutrino luminosities in the early evolution after core bounce. We consider 12-M and 40-M presupernova models and systematically study the effects of (i) rotation, (ii) progenitor structure, and (iii) postbounce neutrino leakage on dynamics, GW, and, neutrino signals. We demonstrate, that the GW signal of rapidly rotating core collapse is practically independent of progenitor mass and precollapse structure. Moreover, we show that the effects of neutrino leakage on the GW signal are strong only in nonrotating or slowly rotating models in which GW emission is not dominated by inner core dynamics. In rapidly rotating cores, core bounce of the centrifugally-deformed inner core excites the fundamental quadrupole pulsation mode of the nascent protoneutron star. The ensuing global oscillations (f ∼ 700 − 800 Hz) lead to pronounced oscillations in the GW signal and correlated strong variations in the rising luminosities of antineutrino and heavy-lepton neutrinos. We find these features in cores that collapse to protoneutron stars with spin periods 2.5 ms and rotational energies sufficient to drive hyper-energetic core-collapse supernova explosions. Hence, GW or neutrino observations of a core collapse event could deliver strong evidence for or against rapid core rotation. Joint GW + neutrino observations would allow to make statements with high confidence. Our estimates suggest that the GW signal should be detectable throughout the Milky Way by advanced laser-interferometer GW observatories, but a water-Cherenkov neutrino detector would have to be of near-megaton size to observe the variations in the early neutrino luminosities from a core collapse event at 1 kpc.

General-Relativistic Three-Dimensional Multi-Group Neutrino Radiation-Hydrodynamics Simulations of Core-Collapse Supernovae

“…Additionally, we carry out lower-resolution simulations in full 3D and octant 3D, which we denote as "s27FL" and "s27OL," respectively. Note that our octant simulations differ from the rotational octant symmetry employed, e.g., in Ott et al (2012), where periodic boundary conditions are enforced on the x−z and y−z planes. This prevents us from following any net rotation and likely changes the character of flows near the boundaries.…”

“…We employ the GR Zelmani CCSN simulation package described in Ott et al (2012Ott et al ( , 2013 and Reisswig et al (2013). Zelmani is based on the open-source Einstein Toolkit (Löffler et al 2012;Mösta et al 2014a) and implements GR hydrodynamics and spacetime evolution with adaptive mesh refinement (AMR).…”

“…Both hydrodynamics and neutrino radiation are evolved and coupled on the same 3D grid. Our simulations are performed with the Zelmani core-collapse simulation package (Ott et al 2012Reisswig et al 2013), which includes GR hydrodynamics and GR spacetime evolution. For the first time, we use a new 3D implementation of the GR spectral two-moment M1 approximation to neutrino transport introduced by Shibata et al (2011).…”

Observing gravitational waves from core-collapse supernovae in the advanced detector era

“…These include, but are not necessarily limited to, turbulent convection driven by negative entropy or lepton gradients and the SASI (e.g., [12][13][14]21,37]), rapidly rotating collapse and bounce (e.g., [17,39,75]), postbounce nonaxisymmetric rotational instabilities (e.g., [38,44,139,140]), rotating collapse to a black hole (e.g., [40]), asymmetric neutrino emission and outflows [12][13][14], and, potentially, rather extreme fragmentation-type instabilities occuring in accretion torii around nascent neutron stars or black holes [43]. A more extensive discussion of GW emission from CCSNe can be found in recent reviews on the subject in Refs.…”

“…The magnitude and time variation of deviations from spherical symmetry, and thus the strength of the emitted GW signal, are uncertain and likely vary from event to event [1,13]. State-of-the-art models, building upon an extensive body of theoretical work on the GW signature of CCSNe, predict GW strains-relative displacements of test masses in a detector on Earth-h of order 10 −23 -10 −20 for a core collapse event at 10 kpc, signal durations of 1 ms − few s, frequencies of ∼1 − few 1000 Hz, and total emitted energies E GW of 10 41 -10 47 erg (corresponding to 10 −12 − 10 −7 M ⊙ c 2 ) [1,13,14,17,27,29,[37][38][39][40]. More extreme phenomenological models, such as long-lasting rotational instabilities of the proto-neutron star and accretion disk fragmentation instabilities, associated with hypernovae and collapsars, suggest much larger strains and more energetic emission, with E GW perhaps up to 10 52 erg (∼0.01M ⊙ c 2 ) [41][42][43][44].…”