Correlated Gravitational Wave and Neutrino Signals from General-Relativistic Rapidly Rotating Iron Core Collapse (1204.0512v2)

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-solar-mass and 40-solar-mass 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, joint GW + neutrino observations of a core collapse event could deliver strong evidence for or against rapid core rotation. [abridged]

• The paper demonstrates that rapid rotation in core collapse produces discernible gravitational wave amplitudes (up to 400 cm) that correlate with neutrino oscillations at ~700-800 Hz.
• The study employs advanced general-relativistic 3D hydrodynamic models with a finite-temperature nuclear equation of state and electron capture schemes to capture deleptonization dynamics.
• These findings indicate that rotational dynamics, rather than progenitor structure, primarily govern the signal correlation, offering new insights into hyper-energetic supernova mechanisms.

Correlated Gravitational Wave and Neutrino Signals from Rotating Core Collapse

The paper presents a comprehensive paper on the gravitational wave (GW) and neutrino signals generated from core collapse supernovae with rotating cores. The authors performed a new set of three-dimensional, general-relativistic hydrodynamic simulations, focusing on rapidly rotating iron core collapse in a supernova context. By exploring both the GW and neutrino signatures, they seek to shed light on the highly dynamic processes involved in such astrophysical events and the implications of rapid core rotation.

Methodological Overview

The paper employed state-of-the-art computational models, utilizing octant symmetry in a three-dimensional setting to simulate the axisymmetric collapse, bounce, and early postbounce evolution. With the inclusion of a microphysical finite-temperature nuclear equation of state and a parameterized scheme for electron capture, the simulations focused on capturing the critical aspects of deleptonization and neutrino interactions. The simulation set included progenitors with 12 and 40 solar masses and investigated a range of initial rotation rates to systematically paper the effects of rotation, progenitor structure, and neutrino processes on the core-collapse dynamics and the resulting signals.

Key Findings

1. Gravitational Waves: The paper finds that GW signals from rapidly rotating core collapse are primarily determined by the inner core's mass and angular momentum at bounce. For rapidly rotating models, the early postbounce GW signals are dominated by inner-core dynamics, which show little sensitivity to postbounce neutrino leakage. The maximum GW amplitudes reach up to 400 cm (equivalent to h+ ~ 1.3e-20 at 10 kpc).
2. Neutrino Signals: The analysis reveals a strong correlation between the GW signal and neutrino emissions, specifically the electron antineutrino and heavy-lepton neutrino luminosities. In the presence of rapid rotation, the fundamental quadrupole pulsation mode of the protoneutron star is excited, leading to global oscillations manifested in both GW and neutrino signals at frequencies of ~700-800 Hz.
3. Dependence on Rotation: The paper underscores the significance of rapid rotation in producing observable oscillations in both GW and neutrino signals. Models with a bounce ratio of rotational to gravitational energy (T/|W|) exceeding 5% excite observable oscillations.
4. Progenitor Independence: The simulation results suggest that the GW and neutrino signals are largely independent of the progenitor's structure and thermodynamics if the models have comparable inner core mass and angular momentum distributions at bounce. This implies that signals are primarily influenced by the rotational dynamics rather than initial core conditions.

Implications and Future Directions

The simultaneous observation of GWs and neutrinos from a galactic core-collapse supernova could provide compelling evidence for rapid core rotation, which could be critical in understanding the mechanisms behind hyper-energetic supernovae and potentially gamma-ray bursts. The paper's techniques and findings also contribute to refining our models of core-collapse supernovae in terms of their neutrino transport and gravitational wave modeling.

While the research takes significant steps forward in understanding correlated GW and neutrino signals, future work should focus on incorporating more advanced neutrino transport methods and full 3D simulations including magnetic fields, to capture non-axisymmetric dynamics without symmetry constraints. This could aid in assessing the true detectability of signals associated with non-axisymmetric instabilities in the core-collapse process. Additionally, exploring a wider parameter space with different nuclear EOS and rotational profiles can further enhance the robustness of the predictions.