arXiv subjects

Haakon Andresen

Publications and source records attributed to Haakon Andresen.

15 recordsLinked to original sources

arXiv2026

Three-dimensional Core-Collapse Supernova Simulations: From shell burning to shock revival

The outcome of core-collapse supernova simulations depends sensitively on the multi-dimensional structure of the progenitor star at the onset of collapse. We perform three-dimensional simulations of the final ~10-15 minutes of stellar evolution for five non-rotating solar-metallicity progenitors with zero-age main-sequence masses of 20, 21.5, 24.5, 26, and 29 solar masses, mapped from one-dimensional MESA models into the FLASH hydrodynamics code. Convection develops in the oxygen-rich layers of all five models, with convective velocities reaching several hundred km/s, and in some models strong convection also develops in the inner silicon- and oxygen-burning shells. For the 24.5 solar mass progenitor, we carry out three core-collapse simulations: one initialised from the fully three-dimensional model, one from its angle-averaged counterpart, and one from the original one-dimensional MESA progenitor. We find that the multi-dimensional progenitor leads to 35 to 50% higher non-radial kinetic energy in the post-shock region and an average shock radius 5 to 10% larger than in the angle-averaged model, and shows the earliest shock revival of the three. The gravitational-wave emission is similar in all three models and strengthens after shock revival, driven by a change in the downflows reaching the protoneutron star rather than by progenitor asymmetries.

astro-ph.HE↗

arXiv2026

Assessing a Template-Based Approach for Core-Collapse Supernova Gravitational-Wave Detection

Gravitational waves from core-collapse supernovae are a promising yet challenging target for detection due to the stochastic and complex nature of these signals. Conventional detection methods for core-collapse supernovae rely on excess energy searches because matched filtering has been hindered by the lack of well-defined waveform templates. However, numerical simulations of core-collapse supernovae have improved our understanding of the gravitational wave signals they emit, which enables us, for the first time, to construct a set of templates that closely resemble predictions from numerical simulations. In this study, we investigate the possibility of detecting gravitational waves from core-collapse supernovae using template-based methods. We construct a theoretically-informed template bank and use it to recover core-collapse supernova signals injected into real LIGO-Virgo-KAGRA detector data. We consider the signals from three state-of-the-art numerical models, simulated with three different codes. We evaluate the detection efficiency of the template-filtering approach and how well the injected signal is reconstructed. For signals whose structure is well captured by our template bank, we recover ~90% of injections at a distance of 1 kpc and ~30-60% at 2 kpc. In contrast, a model whose signal differs significantly from the templates is recovered less efficiently. For many of the recovered events, the underlying signal characteristics can be reconstructed with an accuracy of ~10-20%. We discuss the strengths and limitations of this approach and identify areas for further improvements for template-based methods for supernova gravitational-wave detection. We also present the open-source Python package SynthGrav used to generate the template bank.

astro-ph.HE↗

arXiv2026

The Gravitational-Wave Power Gap in Core-Collapse Supernovae: Insights from 60 Axisymmetric Simulations

We analyse the gravitational-wave emission from 60 two-dimensional core-collapse supernova simulations. The models cover a range of progenitors and equations of state. We focus on the narrow frequency interval in the gravitational-wave spectrum where the emitted power is strongly suppressed (the power gap) and how its central frequency relates to the physical properties of the simulations. We find that the power-gap frequency exhibits strong and systematic correlations with the properties of the inner core of the forming neutron star, for example the sound speed, suggesting that the gap encodes information about the behaviour of matter at extreme densities. We further examine how well several mechanisms proposed in the literature account for the presence and evolution of the gap in our simulations. Finally, we explore a scenario in which the gap arises from destructive interference between a narrow oscillation mode and a broadband background signal, demonstrating that such an interaction can produce a sharp minimum in the emitted gravitational-wave power.

astro-ph.HE↗

arXiv2026

Detecting Gravitational Wave Memory in the Next Galactic Core-Collapse Supernova

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. Errata: The neutrino-induced gravitational waveforms, a component of the total waveforms used to demonstrate the efficacy of the proposed detection method for gravitational wave memory, were computed incorrectly. They were underestimated by a factor of $4π$. As a result, the detection results improve and, most important, our primary conclusions are reinforced. In particular, with the corrected waveforms, see Fig. 1 and Fig. 3, the signal for D9.6-3D is in fact detectable at 1 kiloparsec, see Fig. 6 and Fig. 4. The corrected fit parameters are presented in Table 1. The false alarm probability for all three signals is impacted, as shown in Fig. 5. Fig. 5 demonstrates that our proposed method can reliably detect the D9.6-3D signal at 1 kpc for all cutoff values, but our conclusions regarding the inability to detect this signal at 10 and 100 kpc remain the same. We see a boost in the detectability of the D15-3D and D25-3D signals. We now obtain a lower false alarm probability at 10 and 100 kpc. The authors would like to acknowledge Lella et al. [87] for pointing out the discrepancy between our computed neutrino-induced waveforms and theirs, which prompted us to investigate the discrepancy and which led to the discovery of our error.

astro-ph.HE↗

arXiv2026

Low-Frequency Gravitational Waves in Three-Dimensional Core-Collapse Supernova Models

We discuss the low-frequency gravitational wave signals from three state-of-the-art three-dimensional core-collapse supernova models produced with the \textsc{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 templatablity of this low-frequency signal, which is useful for future work involving matched filtering for signal detection and parameter estimation. Errata: The neutrino-induced gravitational waveforms presented were computed incorrectly. They were underestimated by a factor of $4π$. While the results are impacted, the original conclusions are not. In fact, they are only reinforced. The corrected versions of Figs. 5--7, 11--16, and 19 are given here. The captions of Figs. 5--7, 11, 12, 16, and 19 are not modified. The captions of Figs. 13, 14, and 15 are corrected to the fit parameters for the corrected waveforms. The corrected versions of Tables I--III are given here. There is no correction to the caption. Finally the authors would like to acknowledge Lella et al. [90] for pointing out the discrepancy between our computed neutrino-induced waveforms and theirs, which prompted us to investigate the discrepancy and which led to the discovery of our error.

astro-ph.HE↗

arXiv2026

Linear Gravitational Wave Memory Through the Window of Core-Collapse Supernovae

Low-frequency gravitational waves ($\lessapprox$ 50 Hz) from core-collapse supernovae are becoming more important for current and future gravitational wave studies. This frequency region is dominated by the global morphology of the explosion and the anisotropic emission of neutrinos from the event. This paper serves as a brief review of both theory and detection (prospects) for gravitational waves in the low-frequency region. We discuss the generation of the linear gravitational wave memory sourced from neutrino emission and show results from an example 15 $M_{\odot}$ Solar metallicity progenitor. We also discuss the detection of the linear gravitational wave memory in current detectors, utilizing a combination of a linear predictive filter and matched templating. Finally we will discuss detection prospects in future detectors such as Cosmic Explorer, Einstein Telescope, the Laser Interferometer Space Antenna, and the Lunar Gravitational-wave Antenna.

astro-ph.HE↗

arXiv2026

A Three-Dimensional Exploration of Magnetic Fields, Rotation, and Shock Revival in a $39 M_\odot$ Core-Collapse Supernova Progenitor

We present three-dimensional hydrodynamic and magnetohydrodynamic core-collapse supernova simulations of a rapidly rotating, high-compactness $39 M_\odot$ progenitor to investigate the roles of rotation and magnetic fields in shock revival and outflow morphology. This study is designed to separate neutrino-driven expansion, rotation-induced deformation, and magnetically aided polar outflow within the same progenitor. We evolve three models: a non-rotating hydrodynamic baseline, a rotating hydrodynamic model, and a rotating magnetized model. All three models reach runaway shock expansion within the simulated interval, but with markedly different morphologies and timescales. The magnetized model revives first and develops the clearest bipolar outflow. The rotating non-magnetized model undergoes the latest shock revival and remains comparatively compact at the end of the simulation. The non-rotating model also undergoes shock revival, but subsequently collapses to a black hole about one second after core bounce. In the magnetized model, Maxwell stresses redistribute angular momentum and extract energy from the differential rotation of the protoneutron star, reducing the inner-core spin and helping channel rotational free energy into the emerging polar outflow. Neutrino emission provides an additional, though smaller, angular-momentum sink in both rotating models. We find that rapid rotation and strong magnetic fields can launch an early magnetically aided polar outflow in 3D, while the resulting dynamics remain intrinsically non-axisymmetric. In this extreme progenitor, rotation also provides significant support against prompt black-hole formation, although the longer-term remnant stability remains uncertain beyond the simulated interval.

astro-ph.HE↗

arXiv2026

Black Hole Supernovae Outcomes Across a Wide Progenitor Range

Black hole supernovae (BHSNe), the term we use for core-collapse events in which black hole (BH) formation occurs after shock revival but before the explosion is complete, have emerged as a natural outcome of multidimensional simulations as these calculations have been extended to seconds after bounce. Yet they remain one of the least studied outcomes of core collapse. Here, we assess whether they are confined to the most compact and massive progenitors, whose birth rates are low, or whether they arise systematically across a wider range of progenitor structures. We perform 23 long-term axisymmetric core-collapse simulations of progenitors spanning 19.51-60$\,M_\odot$ and compactnesses $0.31 \lesssim ξ_{2.5} \lesssim 0.63$. We find 18 BHSN outcomes across nearly the full ZAMS mass range considered, corresponding to progenitors with $0.40 \lesssim ξ_{2.5} \lesssim 0.63$. BH formation occurs between $\sim0.7$ s and $\sim4.4$ s after bounce. After BH formation, we continue the evolution with an excision treatment to at least 5000 s. The final explosion energies span $\sim2\times10^{49}$-$3\times10^{51}$ erg, while the final BH gravitational masses span $\sim3$-$26\,M_\odot$. We find a clear remnant-mass trend with CO-core mass, but show that the CO core alone is not an adequate proxy for the final BH mass, especially for progenitors at the low- and high-mass ends of the CO-core distribution. Except for the highest CO-core mass models, no single spherical mass coordinate cleanly separates ejecta from remnant material. Finally, a 2D axisymmetric and a 3D model are compared as we discuss differences between the two geometries.

astro-ph.HE↗

arXiv2024

Black Hole Supernovae, their Equation of State Dependence and Ejecta Composition

Recent literature on core-collapse supernovae suggests that a black hole (BH) can form within $\sim 1$ s of shock revival, while still culminating in a successful supernova. We refer to these as black hole 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 $20\text{-}50$ days after collapse using three axisymmetric models of a $60$ M$_\odot$ 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 $0.06\text{-}0.72\times 10^{51}$ erg with $21.8\text{-}23.3$ M$_\odot$ of ejecta, of which $0\text{-}0.018$ M$_\odot$ is $^{56}$Ni. Compared to expectations from 1D simulations, we find a more nuanced EOS dependence 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.

astro-ph.HE↗

arXiv2024

Gray Two-moment Neutrino Transport: Comprehensive Tests and Improvements for Supernova Simulations

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. 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. 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.

astro-ph.HE↗

arXiv2023

Multi-messenger observations of core-collapse supernovae: Exploiting the standing accretion shock instability

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 $27\ M_\odot$. 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.

astro-ph.HE↗

arXiv2022

Stochastic Gravitational-Wave Background from Stellar Core-Collapse Events

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 non-rotating 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.

gr-qc↗

arXiv2022

Modeling Core-Collapse Supernovae Gravitational-Wave Memory in Laser Interferometric Data

We study the properties of the gravitational wave (GW) emission between $10^{-5}$ Hz 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 multi-messenger 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 slowly 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 semi-analytical 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 were terminated before the neutrino emission has subsided. We discuss how the premature halt of simulations and the non-zero amplitude of the GW memory can induce artefacts 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.

astro-ph.HE↗

arXiv2021

Gravitational-wave Signals From Three-dimensional Supernova Simulations With Different Neutrino-Transport Methods

We compare gravitational-wave (GW) signals from eight three-dimensional simulations of core-collapse supernovae, using two different progenitors with zero-age main sequence masses of 9 and 20 solar masses. The collapse of each progenitor was simulated four times, at two different grid resolutions and with two different neutrino transport methods, using the Aenus-Alcar code. The main goal of this study is to assess the validity of recent concerns that the so-called "Ray-by-Ray+" (RbR+) approximation is problematic in core-collapse simulations and can adversely affect theoretical GW predictions. Therefore, signals from simulations using RbR+ are compared to signals from corresponding simulations using a fully multidimensional (FMD) transport scheme. The 9 solar-mass progenitor successfully explodes, whereas the 20 solar-mass model does not. Both the standing accretion shock instability and hot-bubble convection develop in the postshock layer of the non-exploding models. In the exploding models, neutrino-driven convection in the postshock flow is established around 100 ms after core bounce and lasts until the onset of shock revival. We can, therefore, judge the impact of the numerical resolution and neutrino transport under all conditions typically seen in non-rotating core-collapse simulations. We find excellent qualitative agreement in all GW features. We find minor quantitative differences between simulations, but find no systematic differences between simulations using different transport schemes. Resolution-dependent differences in the hydrodynamic behaviour of low-resolution and high-resolution models have a greater impact on the GW signals than consequences of the different transport methods. Furthermore, increasing the resolution decreases the discrepancies between models with different neutrino transport.

astro-ph.HE↗

arXiv2017

Gravitational Wave Signals from 3D Neutrino Hydrodynamics Simulations of Core-Collapse Supernovae

We present gravitational wave (GW) signal predictions from four 3D multi-group neutrino hydrodynamics simulations of core-collapse supernovae of progenitors with 11.2 Msun, 20 Msun, and 27 Msun. GW emission in the pre-explosion phase strongly depends on whether the post-shock flow is dominated by the standing accretion shock instability (SASI) or convection and differs considerably from 2D models. SASI activity produces a strong signal component below 250 Hz through asymmetric mass motions in the gain layer and a non-resonant coupling to the proto-neutron star (PNS). Both convection- and SASI-dominated models show GW emission above 250 Hz, but with considerably lower amplitudes than in 2D. This is due to a different excitation mechanism for high-frequency l=2 motions in the PNS surface, which are predominantly excited by PNS convection in 3D. Resonant excitation of high-frequency surface g-modes in 3D by mass motions in the gain layer is suppressed compared to 2D because of smaller downflow velocities and a lack of high-frequency variability in the downflows. In the exploding 20 Msun model, shock revival results in enhanced low-frequency emission due to a change of the preferred scale of the convective eddies in the PNS convection zone. Estimates of the expected excess power in two frequency bands suggests that second-generation detectors will only be able to detect very nearby events, but that third-generation detectors could distinguish SASI- and convection-dominated models at distances of ~10 kpc.

astro-ph.HE↗