Core-collapse Supernova Explosions Research Articles

Effect of the Nuclear Equation of State and Relativistic Turbulence on Core-Collapse Supernovae

The nuclear Equation of State (EoS) is an important component in the evolution and subsequent explosion of core collapse supernovae. We make a survey of various equations of state that can be found in the literature and analyze their effect on the explosion. To simulate the supernovae, we use the general relativistic spherically-symmetric code GR1D, modified to take into account the effects of three-dimensional turbulence through a new mixing length theory approach (STIR). We show that the viability of the explosion is quite EoS dependent and that the strength of explosions correlate best with the central entropy density right after bounce and the onset of turbulent mixing in the proto-neutron star.

The Character of Three-Dimensional Core-Collapse Simulation Results

We here in graphical form highlight some of the early phases in the explosion of core-collapse supernovae and the birth of neutron stars. The graphics presented summarizes the results of the almost fifty three-dimensional radiation/hydrodynamic simulations the Princeton group has simulated during the last three years using its state-of-the-art (though still evolving and improving) code Fornax.

Exploring the origin of supermassive black holes with coherent neutrino scattering

Collapsing supermassive stars (M ≳ 3 × 104 M ☉) at high redshifts can naturally provide seeds and explain the origin of the supermassive black holes observed in the centers of nearly all galaxies. During the collapse of supermassive stars, a burst of non-thermal neutrinos is generated with a luminosity that could greatly exceed that of a conventional core collapse supernova explosion. In this work, we investigate the extent to which the neutrinos produced in these explosions can be observed via coherent elastic neutrino-nucleus scattering (CEνNS). Large scale direct dark matter detection experiments provide particularly favorable targets. We find that upcoming \U0001d4aa(100) tonne-scale experiments will be sensitive to the collapse of individual supermassive stars at distances as large as \U0001d4aa(10) Mpc.

Three-dimensional Hydrodynamic Simulations of Convective Nuclear Burning in Massive Stars Near Iron Core Collapse

Abstract Nonspherical structure in massive stars at the point of iron core collapse can have a qualitative impact on the properties of the ensuing core-collapse supernova explosions and the multimessenger signals they produce. Strong perturbations can aid successful explosions by strengthening turbulence in the postshock region. Here we report on a set of 4π 3D hydrodynamic simulations of O- and Si-shell burning in massive star models of varied initial masses using MESA and the FLASH simulation framework. We evolve four separate 3D models for roughly the final 10 minutes prior to and including iron core collapse. We consider initial 1D MESA models with masses of 14, 20, and 25 M ⊙ to survey a range of O/Si-shell density and compositional configurations. We characterize the convective shells in our 3D models and compare them to the corresponding 1D models. In general, we find that the angle-average convective speeds in our 3D simulations near collapse are three to four times larger than the convective speeds predicted by MESA at the same epoch for our chosen mixing length parameter of α MLT = 1.5. In three of our simulations, we observe significant power in the spherical harmonic decomposition of the radial velocity field at harmonic indices of ℓ = 1–3 near collapse. Our results suggest that large-scale modes are common in massive stars near collapse and should be considered a key aspect of presupernova progenitor models.

Application of the Hilbert-Huang transform for analyzing standing-accretion-shock-instability induced gravitational waves in a core-collapse supernova

Through numerical simulations, it is predicted that the gravitational waves (GWs) reflect the characteristics of the core-collapse supernova (CCSN) explosion mechanism. There are multiple GW excitation processes that occur inside a star before its explosion, and it is suggested that the GWs originating from the CCSN have a mode for each excitation process in terms of time-frequency representation. Therefore, we propose an application of the Hilbert-Huang transform (HHT), which is a high-resolution time-frequency analysis method, to analyze these GW modes for theoretically probing and increasing our understanding of the explosion mechanism. The HHT defines frequency as a function of time, and is not bound by the trade-off between time and frequency resolutions. In this study, we analyze a gravitational waveform obtained from a three-dimensional general-relativistic CCSN model that showed a vigorous activity of the standing-accretion-shock-instability (SASI). We succeed in extracting the SASI induced GWs with high resolution on a time-frequency representation using the HHT and we examine their instantaneous frequencies.

Activation thick target yield measurement of Mo100(α,n)Ru103 for studying the weak r -process nucleosynthesis

Background: Light ($30\ensuremath{\le}Z\ensuremath{\le}45$) neutron-rich isotopes are thought to be synthesized in the neutrino-driven ejecta of core-collapse supernovae explosions via the weak $r$ process. Recent nucleosynthesis studies have demonstrated that $(\ensuremath{\alpha},xn)$ reactions play a particularly important role in the production of these isotopes. $\ensuremath{\alpha}$-nucleus optical model potentials ($\ensuremath{\alpha}$-OMPs) are used to model this nucleosynthesis scenario.Purpose: The different $\ensuremath{\alpha}$-OMP model parameters can affect the calculated cross sections by more than an order of magnitude in the relevant energy regions, which affects the production of light neutron-rich isotopes. Consequently, to constrain the astrophysical conditions characterizing the supernovae ejecta, the uncertainty of the nuclear physics input has to be reduced.Methods: The cross section of the $^{100}\mathrm{Mo}(\ensuremath{\alpha},n)^{103}\mathrm{Ru}$ reaction was measured by means of the activation method. 0.5 mm thick molybdenum disks were irradiated with ${E}_{\ensuremath{\alpha}}$ = 7.0 to ${E}_{\ensuremath{\alpha}}$ = 13.0 MeV $\ensuremath{\alpha}$ beams. Thick target yields and reaction cross sections were determined via $\ensuremath{\gamma}$-ray spectroscopy.Results: Cross sections at several energies below the Coulomb barrier were measured, reaching the astrophysically relevant energy region. Large discrepancies between the experimental values and statistical model predictions calculated using the well-known $\ensuremath{\alpha}$-OMPs were found. The measured cross section data could be excellently described by the Atomki-V2 potential. Therefore, this $\ensuremath{\alpha}$-OMP was used to derive the astrophysical reaction rates as a function of temperature.Conclusions: The successful reproduction of the measured cross sections in a wide energy region confirm the reliability of the Atomki-V2 potential. The usage of the new $^{100}\mathrm{Mo}(\ensuremath{\alpha},n)^{103}\mathrm{Ru}$ experimental data along with the Atomki-V2 potential reduces the nuclear uncertainties of the weak $r$-process production yields of nuclei with $36\ensuremath{\le}Z\ensuremath{\le}50$ to a marginal level.

Principles, Detections and Applications of Cosmological Gravitational Waves

Contemporarily, the gravitational wave has played an important role in the field of astronomy. A systematic review of the gravitational wave is presented in this paper. Primarily, the principle of gravitational waves is introduced in both Newton and Einstein’s concept of gravity. Besides, we deduced the solution of Einstein’s field equation. Moreover, we described the detection of gravitational waves with the mechanisms of the two gravitational wave detectors LIGO and Virgo Finally, the applications of gravitational waves are discussed in detecting black hole mergers, neutron star mergers, gamma-ray burst, and core-Collapse Supernova explosion. The gravitational wave could contribute to more scientific findings in the future and solve more mysteries of the Universe.

QCD phase transition drives supernova explosion of a very massive star

The nature of core-collapse supernova (SN) explosions is yet incompletely understood. The present article revisits the scenario in which the release of latent heat due to a first-order phase transition, from normal nuclear matter to the quark–gluon plasma, liberates the necessary energy to explain the observed SN explosions. Here, the role of the metallicity of the stellar progenitor is investigated, comparing a solar metallicity and a low-metallicity case, both having a zero-age main sequence (ZAMS) mass of 75 M_odot . It is found that low-metallicity models belong exclusively to the failed SN branch, featuring the formation of black holes without explosions. It excludes this class of massive star explosions as possible site for the nucleosynthesis of heavy elements at extremely low metallicity, usually associated with the early universe.

Rapid expansion of red giant stars during core helium flash by waves propagation to the envelope and implications to exoplanets

ABSTRACT We assume that the strong convection during core helium flash of low mass red giant branch (RBG) stars excite waves that propagate to the envelope, and find that the energy that these waves deposit in the envelope causes envelope expansion and brightening. We base our assumption and the estimate of the waves’ energy on studies that explored such a process due to the vigorous core convection of massive stars just before they experience a core collapse supernova explosion. Using the stellar evolutionary code mesa, we find that the waves’ energy causes an expansion within few years by tens to hundreds solar radii. Despite the large brightening, we expect the increase in radius and luminosity to substantially enhance mass-loss rate and dust formation. The dust shifts the star to become much redder (to the infrared), and the star might actually become fainter in the visible. The overall appearance is of a faint red transient event that lasts for months to few years. We suggest that in some cases envelope expansion might lead stars that are about to leave the RGB to engulf exoplanets. The extended envelope has a smaller binding energy to a degree that allows planets of several Jupiter masses or more and brown dwarfs to survive the common envelope evolution. We suggest this scenario to account for the planet orbiting the white dwarf (WD) WD 1856+534 (TIC 267574918) and for the WD–brown dwarf binary system ZTFJ003855.0+203025.5.

Rare events of a peculiar thermonuclear supernova that precedes a core-collapse supernova

ABSTRACT We study stellar binary evolution that leads to the formation of a white dwarf (WD) that explodes in a thermonuclear supernova at the termination of a common envelope evolution (CEE) shortly before the core of its companion explodes as a core-collapse supernova (CCSN). The CCSN explosion of the core, which is the remnant of a red supergiant (RSG) star, might take place few months to several years after the explosion of the WD as a thermonuclear supernova, i.e. a Type Ia peculiar supernova (peculiar SN Ia). Using the evolutionary code mesa-binary, we simulate the evolution of binary systems with stars of initial masses of $6\!-\!7.5\, {\rm M}_\odot$. The more massive star, the primary, transfers mass to the secondary star and leaves a CO WD remnant. The secondary becomes massive enough to end in a CCSN. As the secondary evolves to the RSG phase, it engulfs the WD and the system experiences a CEE that ends with a WD–core binary system at an orbital separation of af ≃ 1–5 R⊙. Our simulations show that the core explodes as a CCSN at $t_{\rm CEE-CCSN} \simeq 3000 \!-\! 10^5 {~\rm yr}$ after the CEE. We assume that if the WD accretes helium-rich gas from the core it might explode as an SN Ia in the frame of the double detonation scenario for SNe Ia and peculiar SNe Ia. We predict the very rare occurrence of a peculiar SN Ia followed within months to years by a CCSN.

Nuclear pasta and symmetry energy in the relativistic point-coupling model

Nonuniform structure of low-density nuclear matter, known as nuclear pasta, is expected to appear not only in the inner crust of neutron stars but also in core-collapse supernova explosions and neutron-star mergers. We perform fully three-dimensional calculations of inhomogeneous nuclear matter and neutron-star matter in the low-density region using the Thomas-Fermi approximation. The nuclear interaction is described in the relativistic mean-field approach with the point-coupling interaction, where the meson exchange in each channel is replaced by the contact interaction between nucleons. We investigate the influence of nuclear symmetry energy and its density dependence on pasta structures by introducing a coupling term between the isoscalar-vector and isovector-vector interactions. It is found that the properties of pasta phases in the neutron-rich matter are strongly dependent on the symmetry energy and its slope. In addition to typical shapes like droplets, rods, slabs, tubes, and bubbles, some intermediate pasta structures are also observed in cold stellar matter with a relatively large proton fraction. We find that nonspherical shapes are unlikely to be formed in neutron-star crusts, since the proton fraction obtained in $\beta$ equilibrium is rather small. The inner crust properties may lead to a visible difference in the neutron-star radius.

The KM3NeT potential for the next core-collapse supernova observation with neutrinos

The KM3NeT research infrastructure is under construction in the Mediterranean Sea. It consists of two water Cherenkov neutrino detectors, ARCA and ORCA, aimed at neutrino astrophysics and oscillation research, respectively. Instrumenting a large volume of sea water with sim {6200} optical modules comprising a total of sim {200{,}000} photomultiplier tubes, KM3NeT will achieve sensitivity to sim {10} mathrm{MeV} neutrinos from Galactic and near-Galactic core-collapse supernovae through the observation of coincident hits in photomultipliers above the background. In this paper, the sensitivity of KM3NeT to a supernova explosion is estimated from detailed analyses of background data from the first KM3NeT detection units and simulations of the neutrino signal. The KM3NeT observational horizon (for a 5,sigma discovery) covers essentially the Milky-Way and for the most optimistic model, extends to the Small Magellanic Cloud (sim {60} mathrm{kpc}). Detailed studies of the time profile of the neutrino signal allow assessment of the KM3NeT capability to determine the arrival time of the neutrino burst with a few milliseconds precision for sources up to 5–8 kpc away, and detecting the peculiar signature of the standing accretion shock instability if the core-collapse supernova explosion happens closer than 3–5 kpc, depending on the progenitor mass. KM3NeT’s capability to measure the neutrino flux spectral parameters is also presented.

A DG-IMEX Method for Two-moment Neutrino Transport: Nonlinear Solvers for Neutrino–Matter Coupling*

Abstract Neutrino–matter interactions play an important role in core-collapse supernova (CCSN) explosions, as they contribute to both lepton number and/or four-momentum exchange between neutrinos and matter and thus act as the agent for neutrino-driven explosions. Due to the multiscale nature of neutrino transport in CCSN simulations, an implicit treatment of neutrino–matter interactions is desired, which requires solutions of coupled nonlinear systems in each step of the time integration scheme. In this paper, we design and compare nonlinear iterative solvers for implicit systems with energy-coupling neutrino–matter interactions commonly used in CCSN simulations. Specifically, we consider electron neutrinos and antineutrinos, which interact with static matter configurations through the Bruenn 85 opacity set. The implicit systems arise from the discretization of a nonrelativistic two-moment model for neutrino transport, which employs the discontinuous Galerkin (DG) method for phase-space discretization and an implicit–explicit (IMEX) time integration scheme. In the context of this DG-IMEX scheme, we propose two approaches to formulate the nonlinear systems: a coupled approach and a nested approach. For each approach, the resulting systems are solved with Anderson-accelerated fixed-point iteration and Newton’s method. The performance of these four iterative solvers has been compared on relaxation problems with various degrees of collisionality, as well as proto–neutron star deleptonization problems with several matter profiles adopted from spherically symmetric CCSN simulations. Numerical results suggest that the nested Anderson-accelerated fixed-point solver is more efficient than other tested solvers for solving implicit nonlinear systems with energy-coupling neutrino–matter interactions.

Deep learning for core-collapse supernova detection

The detection of gravitational waves from core-collapse supernova (CCSN) explosions is a challenging task, yet to be achieved, in which it is key the connection between multiple messengers, including neutrinos and electromagnetic signals. In this work, we present a method for detecting these kind of signals based on machine learning techniques. We tested its robustness by injecting signals in the real noise data taken by the Advanced LIGO-Virgo network during the second observation run, O2. We trained a newly developed Mini-Inception Resnet neural network using time-frequency images corresponding to injections of simulated phenomenological signals, which mimic the waveforms obtained in 3D numerical simulations of CCSNe. With this algorithm we were able to identify signals from both our phenomenological template bank and from actual numerical 3D simulations of CCSNe. We computed the detection efficiency versus the source distance, obtaining that, for signal to noise ratio higher than 15, the detection efficiency is 70 % at a false alarm rate lower than 5%. We notice also that, in the case of O2 run, it would have been possible to detect signals emitted at 1 kpc of distance, whilst lowering down the efficiency to 60%, the event distance reaches values up to 14 kpc.

Self-similar adiabatic strong explosion in a medium gravitationally free falling to a point mass

ABSTRACT We develop a generalization to the classical Sedov–Taylor explosion where the medium free falls to a point mass at the centre of the explosion. To verify our analytic results, we compare them to a suite of numerical simulations. We find that there exists a critical energy below which, instead of propagating outward the shock stalls and collapses under gravity. Furthermore, we find that the value of the critical energy threshold decreases when the adiabatic index increases and material is more evenly distributed within the shocked region. We apply this model to the problem of a shock bounce in core collapse supernova, in which the proto-neutron star serves as the point mass. The relation between the threshold energy and the distribution of mass in the shock might help explain how turbulence prevents shock stalling and recession in a core-collapse supernova explosion.

The antesonic condition for the explosion of core-collapse supernovae – II. Rotation and turbulence

ABSTRACT In the problem of steady free fall on to a standing shockwave around a central mass, the ‘antesonic’ condition limits the regime of stable accretion to $c_T^2/v_\mathrm{esc}^2\le 3/16$, where cT is the isothermal sound speed in the subsonic post-shock flow, and vesc is the escape velocity at the shock radius. Above this limit, it is impossible to satisfy both the Euler equation and the shock jump conditions, and the system transitions to a wind. This physics explains the existence of a critical neutrino luminosity in steady-state models of accretion in the context of core-collapse supernovae. Here, we extend the antesonic condition to flows with rotation and turbulence using a simple one-dimensional formalism. Both effects decrease the critical post-shock sound speed required for explosion. While quite rapid rotation is required for a significant change to the critical condition, we show that the level of turbulence typically achieved in supernova simulations can greatly impact the critical value of $c_T^2/v_\mathrm{esc}^2$. A core angular velocity corresponding to a millisecond rotation period after contraction of the proto-neutron star results in only a ∼5 per cent reduction of the critical curve. In contrast, near-sonic turbulence with specific turbulent kinetic energy $K/c_T^2=0.5-1$, leads to a decrease in the critical value of $c_T^2/v_{\rm esc}^2$ by ∼20 to 40 per cent. This analysis provides a framework for understanding the role of post-shock turbulence in instigating explosions in models that would otherwise fail and helps explain why multidimensional simulations explode more easily than their one-dimensional counterparts.

Phenomenological quark-hadron equations of state with first-order phase transitions for astrophysical applications

In the current work an equation of state model with a first-order phase transition for astrophysical applications is presented. The model is based on a two-phase approach for quark-hadron phase transitions, which leads by construction to a first-order phase transition. The resulting model has already been successfully used in several astrophysical applications, such as cold neutron stars, core-collapse supernova explosions and binary neutron star mergers. Main goal of this work is to present the details of the model, discuss certain features and eventually publish it in a tabulated form for further use.

On rare core collapse supernovae inside planetary nebulae

ABSTRACT We conduct simulations using mesa of the reverse formation of a white dwarf (WD)–neutron star (NS) binary system in which the WD forms before the NS. We conclude that a core collapse supernova (CCSN) explosion might occur inside a planetary nebula (PN) only if a third star forms the PN. In this WD–NS reverse binary evolution, the primary star evolves and transfers mass to the secondary star, forms a PN, and leaves a WD remnant. If the mass-transfer brings the secondary star to have a mass of $\gtrsim 8\, \mathrm{ M}_\odot$ before it develops a helium core, and if the secondary does not suffer an enhanced mass-loss before it develops a massive helium core, e.g. by mass-transfer, it explodes as a CCSN and leaves an NS remnant. The time period from the formation of the PN by the primary to the explosion of the secondary is $\gtrsim 10^6 {~\rm yr}$. By that time, the PN has long dispersed into the interstellar medium. In a binary system with nearly equal-mass components, the first mass-transfer episode takes place after the secondary star has developed a helium core and it ends its life forming a PN and a WD. The formation of a CCSN inside a PN (CCSNIP) requires the presence of a third star. The third star should be less massive than the secondary star but by no more than few ×0.01 M⊙. We estimate that the rate of CCSNIP is ≈10−4 times the rate of all CCSNe.

NGC 2770: High supernova rate due to interaction

Context. Galaxies that hosted many core-collapse supernova (SN) explosions can be used to study the conditions necessary for the formation of massive stars. NGC 2770 was dubbed an SN factory because it hosted four core-collapse SNe in 20 years (three type Ib and one type IIn). Its star formation rate (SFR) was reported to not be enhanced and, therefore, not compatible with such a high SN rate. Aims. We aim to explain the high SN rate of NGC 2770. Methods. We used archival H I line data for NGC 2770 and reinterpreted the Hα and optical continuum data. Results. Even though the continuum-based SFR indicators do not yield high values, the dust-corrected Hα luminosity implies a high SFR, consistent with the high SN rate. Such a disparity between the SFR estimators is an indication of recently enhanced star formation activity because the continuum indicators trace long timescales of the order of 100 Myr, unlike the line indicators, which trace timescales of the order of 10 Myr. Hence, the unique feature of NGC 2770 compared to other galaxies is the fact that it was observed very shortly after the enhancement of the SFR. It also has high dust extinction, E(B − V) above 1 mag. We provide support for the hypothesis that the increased SFR in NGC 2770 is due to the interaction with its companion galaxies. We report an H I bridge between NGC 2770 and its closest companion and the existence of a total of four companions within 100 kpc (one identified for the first time). There are no clear H I concentrations close to the positions of SNe in NGC 2770 such as those detected for hosts of gamma-ray bursts (GRBs) and broad-lined SNe type Ic (IcBL). This suggests that the progenitors of type Ib SNe are not born out of recently accreted atomic gas, as was suggested for GRB and IcBL SN progenitors.

Accuracy of the relativistic Cowling approximation in protoneutron star asteroseismology

The relativistic Cowling approximation, where the metric perturbations are neglected during the fluid oscillations, is often adopted for considering the gravitational waves from the protoneutron stars (PNSs) provided via core-collapse supernova explosions. In this study, we evaluate how the Cowling approximation works well by comparing the frequencies with the Cowling approximation to those without the approximation. Then, we find that the behavior of the frequencies with the approximation is qualitatively the same way as that without the approximation, where the frequencies with the approximation can totally be determined within $\sim 20\%$ accuracy. In particular, the fundamental mode with the Cowling approximation is overestimated. In addition, we also discuss the damping time of various eigenmodes in gravitational waves from the PNSs, where the damping time for the PNSs before the avoided crossing between the $f$- and $g_1$-modes, is quite different from that for cold neutron stars, but it is more or less similar to that for cold neutron stars in the later phase. The damping time is long enough compared to the typical time interval of short-Fourier transformation that often used in the analysis, and that ideally guarantees the validity of the transformation.