Recent literature on core-collapse supernovae suggests that a black hole (BH) can form within ∼1 s of shock revival, while still culminating in a successful supernova. We refer to these as BH supernovae, as they are distinct from other BH formation channels in both timescale and impact on the explosion. We simulate these events self-consistently from core collapse until 20–50 days after collapse using three axisymmetric models of a 60 M_⊙ zero-age main-sequence progenitor star and investigate how the composition of the ejecta is impacted by the BH formation. We employ Skyrme-type equations of state (EOSs) and vary the uncertain nucleonic effective mass, which affects the pressure inside the proto–neutron star through the thermal part of the EOS. This results in different BH formation times and explosion energies at BH formation, yielding final explosion energies between 0.06 and 0.72 × 10⁵¹ erg with 21.8–23.3 M_⊙ of ejecta, of which 0–0.018 M_⊙ is ⁵⁶Ni. Compared to expectations from 1D simulations, we find more nuanced EOS dependences of the explosion dynamics, the mass of the BH remnant, and the elemental composition of the ejecta. We investigate why the explosions survive despite the massive overburden and link the shape of the diagnostic energy curve and character of the ejecta evolution to the progenitor structure.

We discuss the low-frequency gravitational wave signals from three state-of-the-art three-dimensional core-collapse supernova models produced with the chimera supernova code. We provide a detailed derivation of the gravitational wave signal sourced from the anisotropic emission of neutrinos and provide the total (fluid-sourced and neutrino-sourced) gravitational waves signal generated in our models. We discuss the templatability of this low-frequency signal, which is useful for future work involving matched filtering for signal detection and parameter estimation.

We present an approach to detecting (linear) gravitational wave memory in a Galactic core-collapse supernova using current interferometers. Gravitational wave memory is an important prediction of general relativity that has yet to be confirmed. Our approach uses a combination of linear prediction filtering and matched filtering. We present the results of our approach on data from core-collapse supernova simulations that span a range of progenitor mass and metallicity. We are able to detect gravitational wave memory out to 10 kpc. We also present the false alarm probabilities assuming an on-source window compatible with the presence of a neutrino detection.

Aims. In this work we extended an energy-integrated neutrino transport method to facilitate efficient, yet precise, modeling of compact astrophysical objects. We particularly focus on core-collapse supernovae.

Methods. We implemented a gray neutrino-transport framework from the literature into FLASH and performed a detailed evaluation of its accuracy in core-collapse supernova simulations. Based on comparisons with results from simulations using energy-dependent neutrino transport, we incorporated several improvements to the original scheme.

Results. Our analysis shows that our gray neutrino transport method successfully reproduces key aspects from more complex energy-dependent transport across a variety of progenitors and equations of state. We find both qualitative and reasonable quantitative agreement with multi-group M1 transport simulations. However, the gray scheme tends to slightly favor shock revival. In terms of gravitational wave and neutrino signals, there is a good alignment with the energy-dependent transport, although we find 15–30% discrepancies in the average energy and luminosity of heavy-lepton neutrinos. Simulations using the gray transport are around four times faster than those using energy-dependent transport.

The gravitational wave (GW) and neutrino signals from core-collapse supernovae (CCSNe) are expected to carry pronounced imprints of the standing accretion shock instability (SASI). We investigate whether the correlation between the SASI signatures in the GW and neutrino signals could be exploited to enhance the detection efficiency of GWs. We rely on a benchmark full-scale three-dimensional CCSN simulation with zero-age main sequence mass of 27M⊙. Two search strategies are explored: 1. the inference of the SASI frequency range and/or time window from the neutrino event rate detectable at the IceCube Neutrino Observatory; 2. the use of the neutrino event rate to build a matched filter template. We find that incorporating information from the SASI modulations of the IceCube neutrino event rate can increase the detection efficiency compared to standard GW excess energy searches up to 30% for nearby CCSNe. However, we do not find significant improvements in the overall GW detection efficiency for CCSNe more distant than 1.5 kpc. We demonstrate that the matched filter approach performs better than the unmodeled search method, which relies on a frequency bandpass inferred from the neutrino signal. The improved detection efficiency provided by our matched filter method calls for additional work to outline the best strategy for the first GW detection from CCSNe.

We study the properties of the gravitational-wave (GW) emission between 10−5 and 50 Hz (which we refer to as low-frequency emission) from core-collapse supernovae, in the context of studying such signals in laser interferometric data as well as performing multimessenger astronomy. We pay particular attention to the GW linear memory, which is when the signal amplitude does not return to zero after the GW burst. Based on the long-term simulation of a core-collapse supernova of a solar-metallicity star with a zero-age main sequence mass of 15 solar masses, we discuss the spectral properties, the memory’s dependence on observer position, and the polarization of low-frequency GWs from non- (or slowly) rotating core-collapse supernovae. We make recommendations on the angular spacing of the orientations needed to properly produce results that are averaged over multiple observer locations by investigating the angular dependence of the GW emission. We propose semianalytical models that quantify the relationship between the bulk motion of the supernova shock wave and the GW memory amplitude. We discuss how to extend neutrino-generated GW signals from numerical simulations that are terminated before the neutrino emission has subsided. We discuss how the premature halt of simulations and the nonzero amplitude of the GW memory can induce artifacts during the data analysis process. Lastly, we also investigate potential solutions and issues in the use of taperings for both ground- and space-based interferometers.

We estimate the stochastic gravitational-wave background arising from all stellar core-collapse events in the universe based on the gravitational-wave signal predictions of recent numerical simulations. We focus on waveforms from slowly or nonrotating stars and include rapidly rotating, highly massive progenitors as extreme case limits. Our most realistic estimates are more than one hundred times below the sensitivity of third-generation terrestrial gravitational-wave detectors and likely weaker than cosmological contributions to the stochastic gravitational-wave background.