Anisotropic Neutrino Emission Research Articles

Interplay between neutrino kicks and hydrodynamic kicks of neutron stars and black holes

Neutron stars (NSs) are observed with high space velocities and elliptical orbits in binaries. The magnitude of these effects points to natal kicks that originate from asymmetries during the supernova (SN) explosions. Using a growing set of long-time 3D SN simulations with the Prometheus-Vertex code, we explore the interplay of NS kicks that are induced by asymmetric neutrino emission and by asymmetric mass ejection. Anisotropic neutrino emission can arise from a large-amplitude dipolar convection asymmetry inside the proto-NS (PNS) termed LESA (Lepton-number Emission Self-sustained Asymmetry) and from aspherical accretion downflows around the PNS, which can lead to anisotropic neutrino emission (absorption/scattering) with a neutrino-induced NS kick roughly opposite to (aligned with) the kick by asymmetric mass ejection. In massive progenitors, hydrodynamic kicks can reach up to more than 1300 km s−1, whereas our calculated neutrino kicks reach (55–140) km s−1 (estimated upper bounds of (170–265) km s−1) and only ∼(10–50) km s−1, if LESA is the main cause of asymmetric neutrino emission. Therefore, hydrodynamic NS kicks dominate in explosions of high-mass progenitors, whereas LESA-induced neutrino kicks dominate for NSs born in low-energy SNe of the lowest-mass progenitors, when these explode nearly spherically. Our models suggest that the Crab pulsar with its velocity of ∼160 km s−1, if born in the low-energy explosion of a low-mass, single-star progenitor, should have received a hydrodynamic kick in a considerably asymmetric explosion. Black holes, if formed by the collapse of short-lived PNSs and solely kicked by anisotropic neutrino emission, obtain velocities of only some km s−1.

The gravitational-wave emission from the explosion of a 15 solar mass star with rotation and magnetic fields

ABSTRACT Gravitational waveform predictions from 3D simulations of explosions of non-rotating massive stars with no magnetic fields have been extensively studied. However, the impact of magnetic fields and rotation on the core-collapse supernova gravitational-wave signal is not well understood beyond the core-bounce phase. Therefore, we perform four magnetohydrodynamical simulations of the explosion of a $15\, {\rm M}_{\odot }$ star with the SFHx and SFHo equations of state. All of the models start with a weak magnetic field strength of $10^{8}$ G, and two of the models are rapidly rotating. We discuss the impact of the rotation and magnetic fields on the gravitational-wave signals. We find that the weak pre-collapse fields do not have a significant impact on the gravitational-wave signal amplitude. With rapid rotation, the f/g-mode trajectory can change in shape, and the dominant emission band becomes broader. We include the low-frequency memory component of the gravitational-wave signal from both matter motions and neutrino emission anisotropy. We show that including the gravitational waves from anisotropic neutrino emission increases the supernova gravitational-wave detection distances for the Einstein Telescope. The gravitational waves from anisotropic neutrino emission would also be detectable out to Mpc distances by a moon-based gravitational-wave detector.

Three-dimensional GRMHD simulations of rapidly rotating stellar core collapse

ABSTRACT We present results from fully general relativistic (GR), three-dimensional (3D), neutrino-radiation magneto-hydrodynamic (MHD) simulations of stellar core collapse of a 20 M⊙ star with spectral neutrino transport. Our focus is to study the gravitational-wave (GW) signatures from the magnetorotationally (MR)-driven models. By parametrically changing the initial angular velocity and the strength of the magnetic fields in the core, we compute four models. Among our models, only those with cores having an initial magnetic field strength of 1012 G and rotation rates of 1 or 2 rad s−1 produce MHD jets. Seen from the direction perpendicular to the rotational axis, a characteristic waveform is obtained exhibiting a monotonic time increase in the wave amplitude. As previously identified, this stems from the propagating MHD outflows along the axis. We show that the GW amplitude from anisotropic neutrino emission becomes more than one order-of-magnitude bigger than that from the matter contribution, whereas seen from the rotational axis, both of the two components are in the same order-of-magnitudes. Due to the memory effect, the frequency of the neutrino GW from our full-fledged 3D-MHD models is in the range less than ∼10 Hz. Toward the future GW detection for a Galactic core-collapse supernova, if driven by the MR mechanism, the planned next-generation detector as DECIGO is urgently needed to catch the low-frequency signals.

Supernova Fallback as Origin of Neutron Star Spins and Spin-kick Alignment

Abstract Natal kicks and spins are characteristic properties of neutron stars (NSs) and black holes (BHs). Both offer valuable clues to dynamical processes during stellar core collapse and explosion. Moreover, they influence the evolution of stellar multiple systems and the gravitational-wave signals from their inspiral and merger. Observational evidence of a possibly generic spin-kick alignment has been interpreted as an indication that NS spins are either induced with the NS kicks or inherited from the progenitor rotation, which thus might play a dynamically important role during stellar collapse. Current three-dimensional supernova simulations suggest that NS kicks are transferred in the first seconds of the explosion, mainly by anisotropic mass ejection and, on a secondary level, anisotropic neutrino emission. By contrast, the NS spins are only determined minutes to hours later by the angular momentum associated with the fallback of matter that does not become gravitationally unbound in the supernova. Here, we propose a novel scenario to explain spin-kick alignment as a consequence of tangential vortex flows in the fallback matter that is accreted mostly from the direction of the NS’s motion. For this effect the initial NS kick is crucial, because it produces a growing offset of the NS away from the explosion center, thus promoting one-sided accretion. In this new scenario conclusions based on traditional concepts are reversed. For example, pre-kick NS spins are not required, and rapid progenitor core rotation can hamper spin-kick alignment. We also discuss implications for natal BH kicks and the possibility of tossing the BH’s spin axis during its formation.

Anisotropic Multimessenger Signals from Black Hole Neutrino-dominated Accretion Flows with Outflows in Binary Compact Object Mergers

Abstract A black hole (BH) hyperaccretion system might be born after the merger of a BH and a neutron star (NS) or a binary NS (BNS). In the case of a high mass accretion rate, the hyperaccretion disk is in a state of neutrino-dominated accretion flow (NDAF) and emits numerous anisotropic MeV neutrinos. Only a small fraction of these neutrinos annihilates in the space outside of the disk and then launches ultrarelativistic jets that break away from the merger ejecta to power gamma-ray bursts. Mergers and their remnants are generally considered sources of gravitational waves (GWs), neutrinos, and kilonovae. Anisotropic neutrino emission and anisotropic high-velocity material outflows from central BH–NDAF systems can also trigger strong GWs and luminous disk-outflow-driven (DOD) kilonovae, respectively. In this paper, the anisotropic multimessenger signals from NDAFs with outflows, including DOD kilonovae, MeV neutrinos, and GWs, are presented. According to the results, the typical AB magnitude of the DOD kilonovae is lower than that of astronomical transient AT 2017gfo at the same distance, and it decreases with increasing viewing angles and its anisotropy is not sensitive to the outflow mass distribution but mainly determined by the velocity distribution. Since neutrinos with ≳10 MeV are mainly produced in the inner region of the disk, they will be dramatically deflected to a large viewing angle by relativity effects. Moreover, the strains of GWs induced by anisotropic neutrinos increase with increasing viewing angles. The accumulation of multimessenger detection of the BNS/BH–NS mergers with different viewing angles might further verify the existence of NDAFs with outflows.

Neutrinos and gravitational waves from magnetized neutrino-dominated accretion discs with magnetic coupling

ABSTRACT Gamma-ray bursts (GRBs) might be powered by black hole (BH) hyperaccretion systems via the Blandford–Znajek (BZ) mechanism or neutrino annihilation from neutrino-dominated accretion flows (NDAFs). Magnetic coupling (MC) between the inner disc and BH can transfer angular momentum and energy from the fast-rotating BH to the disc. The neutrino luminosity and neutrino annihilation luminosity are both efficiently enhanced by the MC process. In this paper, we study the structure, luminosity, MeV neutrinos, and gravitational waves (GWs) of magnetized NDAFs (MNDAFs) under the assumption that both the BZ and MC mechanisms are present. The results indict that the BZ mechanism will compete with the neutrino annihilation luminosity to trigger jets under the different partitions of the two magnetic mechanisms. The typical neutrino luminosity and annihilation luminosity of MNDAFs are definitely higher than those of NDAFs. The typical peak energy of neutrino spectra of MNDAFs is higher than that of NDAFs, but similar to those of core-collapse supernovae. Moreover, if the MC process is dominant, then the GWs originating from the anisotropic neutrino emission will be stronger particularly for discs with high accretion rates.

Black Hole Hyperaccretion in Collapsars. II. Gravitational Waves

Abstract As progenitors of gamma-ray bursts (GRBs), the core collapse of massive stars and the coalescence of compact object binaries are believed to be powerful sources of gravitational waves (GWs). In the collapsar scenario, a rotating stellar-mass black hole (BH) surrounded by a hyperaccretion disk might be active in the center of a massive collapsar, which is one of the plausible central engines of long GRBs. Such a BH hyperaccretion disk would be in a state of a neutrino-dominated accretion flow (NDAF) at the initial stage of the accretion process; meanwhile, the jets attempt to break out from the envelope and circumstellar medium to power GRBs. In addition to collapsars, BH hyperaccretion systems are important sources of neutrinos and GWs. In this paper, we investigate the GW emission generated by the anisotropic neutrino emission from NDAFs in collapsar scenarios. As the results indicate, the typical frequency of GWs is ∼1–100 Hz, and the masses and metallicities of the progenitor stars have slight effects on the GW strains. The GWs from NDAFs might be detected by operational or planned detectors at a distance of 10 kpc. Moreover, comparisons of the detectable GWs from collapsars, NDAFs, and GRB jets (internal shocks) are displayed. By combining the electromagnetic counterparts, neutrinos, and GWs, one may constrain the characteristics of collapsars and central BH accretion systems.

Detailed X-Ray Mapping of the Shocked Ejecta and Circumstellar Medium in the Galactic Core-collapse Supernova Remnant G292.0+1.8

Abstract G292.0+1.8 (G292) is a young (∼3000 yr), Galactic textbook-type core-collapse supernova remnant. It is characterized by X-ray, optical and infrared emission from ejecta and circumstellar medium (CSM) features, and contains a pulsar (PSR J1124-5916) and pulsar wind nebula that have been observed in X-rays and radio. Previous studies have revealed a complex, dynamically evolving, oxygen-rich remnant, a striking relic from the explosion of a massive star. Here, using our deep (530 ks) Chandra ACIS data, we present high spatial-resolution maps (based on a regional grid size of a few arcsecond) of the shocked CSM and metal-rich ejecta in G292. We make the first Chandra-detection of Fe-rich ejecta in G292. We identify the X-ray counterpart of the northern equatorial belt, a component of a ring-like CSM structure identified earlier in the infrared band. We show the detailed spatial distributions of ejecta enriched in O, Ne, Mg, Si, S, and Fe. We find that the bulk of the Si, S, and Fe-rich X-ray-emitting ejecta are located in the northwestern hemisphere of the remnant, opposite to the pulsar’s projected angular displacement to the southeast from the SNR’s center. This suggests that the pulsar’s kick may have originated from gravitational and hydrodynamic forces during an asymmetric explosion, rather than from anisotropic neutrino emission. Based on abundance ratios and our estimated CSM and ejecta masses, we constrain the progenitor mass to 13 M ⊙ ≲ M ≲ 30 M ⊙

Hydrodynamical Neutron-star Kicks in Electron-capture Supernovae and Implications for the CRAB Supernova

Abstract Neutron stars (NSs) obtain kicks, typically of several 100 km s−1, at birth. The gravitational tugboat mechanism can explain these kicks as consequences of asymmetric mass ejection during the supernova (SN) explosion. Support for this hydrodynamic explanation is provided by observations of SN remnants with associated NSs, which confirm the prediction that the bulk of the explosion ejecta, particularly the chemical elements between silicon and the iron group, are dominantly expelled in the hemisphere opposite to the direction of the NS kick. Here, we present a large set of two- and three-dimensional explosion simulations of electron-capture SNe, considering explosion energies between ∼3 × 1049 erg and ∼1.6 × 1050 erg. We find that the fast acceleration of the SN shock in the steep density gradient delimiting the O–Ne–Mg core of the progenitor enables such a rapid expansion of neutrino-heated matter that the growth of neutrino-driven convection freezes out quickly in a high-mode spherical harmonics pattern. Because the corresponding momentum asymmetry of the ejecta is very small and the gravitational acceleration by the fast-expanding ejecta abates rapidly, the NS kick velocities are a few km s−1, at most. The extremely low core compactness of O–Ne–Mg-core progenitors therefore favors hydrodynamic NS kicks much below the ∼160 km s−1 measured for the Crab pulsar. This suggests either that the Crab Nebula is not the remnant of an electron-capture SN, but rather of a low-mass iron-core progenitor; or that the Crab pulsar was not accelerated by the gravitational tugboat mechanism, but instead received its kick by a non-hydrodynamic mechanism such as, e.g., anisotropic neutrino emission.

Kicks of magnetized strange quark stars induced by anisotropic emission of neutrinos

We study the anisotropic neutrino emission from the core of neutron stars induced by the star's magnetic field. We model the core as made out of a magnetized ideal gas of strange quark matter and implement the conditions for stellar equilibrium in this environment. The calculation is performed without resorting to analytical simplifications and for temperature, density and magnetic field values corresponding to typical conditions for a neutron star's evolution. The anisotropic neutrino emission produces a rocket effect that contributes to the star's kick velocity. We find that the computed values for the kick velocity lie within the range of the observed values, reaching velocities of the order of $\sim1000$ km s$^{-1}$ for magnetic fields between $10^{15}-10^{18}$ G and radii of 20 to 5 km, respectively.

Intermediate-mass Elements in Young Supernova Remnants Reveal Neutron Star Kicks by Asymmetric Explosions

Abstract The birth properties of neutron stars (NSs) yield important information about the still-debated physical processes that trigger the explosion as well as on intrinsic neutron-star physics. These properties include the high space velocities of young neutron stars with average values of several 100 km s−1, with an underlying “kick” mechanism that is not fully clarified. There are two competing possibilities that could accelerate NSs during their birth: anisotropic ejection of either stellar debris or neutrinos. Here we present new evidence from X-ray measurements that chemical elements between silicon and calcium in six young gaseous supernova remnants are preferentially expelled opposite to the direction of neutron star motion. There is no correlation between the kick velocities and magnetic field strengths of these neutron stars. Our results support a hydrodynamic origin of neutron-star kicks connected to asymmetric explosive mass ejection, and they conflict with neutron-star acceleration scenarios that invoke anisotropic neutrino emission caused by particle and nuclear physics in combination with very strong neutron-star magnetic fields.

Neutron stars velocities and magnetic fields

We study a model that explain neutron stars velocities due to the anisotropic emission of neutrinos. Strong magnetic fields present in neutron stars are the source of the anisotropy in the system. To compute the velocity of the neutron star we model its core as composed by strange quark matter and analice the properties of a magnetized quark gas at finite temperature and density. Specifically we have obtained the electron polarization and the specific heat of magnetized fermions as a functions of the temperature, chemical potential and magnetic field which allow us to study the velocity of the neutron star as a function of these parameters.

Comparison of Gravitational Waves from Central Engines of Gamma-Ray Bursts: Neutrino-dominated Accretion Flows, Blandford–Znajek Mechanisms, and Millisecond Magnetars

Abstract Neutrino-dominated accretion flow (NDAF) around a rotating stellar-mass black hole (BH) is one of the plausible candidates for the central engines of gamma-ray bursts (GRBs). Because the time-variant and anisotropic emission of neutrinos from NDAFs leads to GRB variability, NDAFs can be regarded as the sources of strong gravitational waves (GWs). We calculate the dependences of the GW strains on both the BH spin and the accretion rate. We demonstrate that, for typical GRBs with either a single pulse or multiple pulses, the GWs from NDAFs might be detected at a distance of ∼100 kpc/∼1 Mpc by the advanced LIGO/Einstein Telescope with a typical frequency of ∼ 10 – 100 Hz . Besides NDAFs, the other two competitive candidates for the GRB central engine are the Blandford–Znajek (BZ) mechanism and millisecond magnetars. We explore the GW signals from these two as well, and compare the corresponding results with NDAFs’. We find that for a certain GRB, the possible detected distance from NDAFs is about two orders of magnitude higher than that from the BZ mechanism, but at least two orders of magnitude lower than that from magnetars. The typical GW frequency for the BZ mechanism is the same as that of NDAFs, ∼ 10 – 100 Hz , while the typical frequency for magnetars is ∼2000 Hz. Therefore, the GWs released by the central engines of adjacent GRBs might be used to determine whether there is an NDAF, a BZ jet, or a magnetar in the GRB center.

Comparing Neutron Star Kicks to Supernova Remnant Asymmetries

Abstract Supernova explosions are inherently asymmetric and can accelerate new-born neutron stars (NSs) to hundreds of km s−1. Two prevailing theories to explain NS kicks are ejecta asymmetries (e.g., conservation of momentum between NS and ejecta) and anisotropic neutrino emission. Observations of supernova remnants (SNRs) can give us insights into the mechanism that generates these NS kicks. In this paper, we investigate the relationship between NS kick velocities and the X-ray morphologies of 18 SNRs observed with the Chandra X-ray Observatory and the Röntgen Satellite (ROSAT). We measure SNR asymmetries using the power-ratio method (a multipole expansion technique), focusing on the dipole, quadrupole, and octupole power ratios. Our results show no correlation between the magnitude of the power ratios and NS kick velocities, but we find that for Cas A and G292.0+1.8, whose emission traces the ejecta distribution, their NSs are preferentially moving opposite to the bulk of the X-ray emission. In addition, we find a similar result for PKS 1209–51, CTB 109, and Puppis A; however, their emission is dominated by circumstellar/interstellar material, so their asymmetries may not reflect their ejecta distributions. Our results are consistent with the theory that NS kicks are a consequence of ejecta asymmetries as opposed to anisotropic neutrino emission. In the future, additional observations to measure NS proper motions within ejecta-dominated SNRs are necessary to robustly constrain the NS kick mechanism.

Gravitational wave signatures from low-mode spiral instabilities in rapidly rotating supernova cores

We study properties of gravitational waves (GWs) from the rotating core collapse of a $15{M}_{\ensuremath{\bigodot}}$ star by performing three-dimensional general-relativistic hydrodynamic simulations with an approximate neutrino transport. By parametrically changing the precollapse angular momentum, we focus on the effects of rotation on the GW signatures in the early postbounce evolution. Regarding three-flavor neutrino transport, we solve the energy-averaged set of radiation energy and momentum based on the Thorne's momentum formalism. In addition to the gravitational quadrupole radiation from matter motions, we take into account GWs from anisotropic neutrino emission. With these computations, our results present supporting evidence for the previous anticipation that nonaxisymmetric instabilities play an essential role in determining the postbounce GW signatures. During prompt convection, we find that the waveforms show narrow-band and highly quasiperiodic signals which persist until the end of simulations. We point out that such features reflect the growth of the one-armed spiral modes. The typical frequency of the quasiperiodic waveforms can be well explained by the propagating acoustic waves between the stalled shock and the rotating proto-neutron star surface, which suggests the appearance of the standing-accretion-shock instability. Although the GW signals exhibit strong variability between the two polarizations and different observer directions, they are within the detection limits of next-generation detectors such as KAGRA and Advanced LIGO, if the source with sufficient angular momentum is located in our Galaxy.

Natal kicks of stellar mass black holes by asymmetric mass ejection in fallback supernovae

Integrating trajectories of low-mass X-ray binaries containing black holes within the Galactic potential, Repetto, Davies & Sigurdsson recently showed that the large distances of some systems above the Galactic plane can only be explained if black holes receive appreciable natal kicks. Surprisingly, they found that the distribution of black hole kick velocities (rather than that of the momenta) should be similar to that of neutron stars. Here I argue that this result can be understood if neutron star and black hole kicks are a consequence of large-scale asymmetries created in the supernova ejecta by the explosion mechanism. The corresponding anisotropic gravitational attraction of the asymmetrically expelled matter does not only accelerate new-born neutron stars by the "gravitational tug-boat mechanism". It can also lead to delayed black-hole formation by asymmetric fallback of the slowest parts of the initial ejecta onto the transiently existing neutron star, in course of which the momentum of the black hole can grow with the fallback mass. Black hole kick velocities will therefore not be reduced by the ratio of neutron star to black hole mass as would be expected for kicks caused by anisotropic neutrino emission of the nascent neutron star.

Three-dimensional neutrino-driven supernovae: Neutron star kicks, spins, and asymmetric ejection of nucleosynthesis products

We present 3D simulations of supernova (SN) explosions of nonrotating stars, triggered by the neutrino-heating mechanism with a suitable choice of the core-neutrino luminosity. Our results show that asymmetric mass ejection caused by hydrodynamic instabilities can accelerate the neutron star (NS) up to recoil velocities of more than 700 km/s by the "gravitational tug-boat mechanism", which is enough to explain most observed pulsar velocities. The associated NS spin periods are about 100 ms to 8 s without any correlation between spin and kick magnitudes or directions. This suggests that faster spins and a possible spin-kick alignment might require angular momentum in the progenitor core prior to collapse. Our simulations for the first time demonstrate a clear correlation between the size of the NS kick and anisotropic ejection of heavy elements created by explosive burning behind the shock. In the case of large NS kicks the explosion is significantly stronger opposite to the kick vector. Therefore the bulk of the Fe-group elements, in particular nickel, is ejected mostly in large clumps against the kick direction. This contrasts with the case of low recoil velocity, where the Ni-rich lumps are more isotropically distributed. Intermediate-mass nuclei heavier than Si (like Ca and Ti) also exhibit a significant enhancement in the hemisphere opposite to the direction of fast NS motion, while the distribution of C, O, and Ne is not affected, and that of Mg only marginally. Mapping the spatial distribution of the heavy elements in SN remnants with identified pulsar motion may offer an important diagnostic test of the kick mechanism. Different from kick scenarios based on anisotropic neutrino emission, our hydrodynamical acceleration model predicts enhanced ejection of Fe-group elements and of their nuclear precursors in the direction opposite to the NS recoil. (abridged)

GRAVITATIONAL WAVE SIGNATURES OF HYPERACCRETING COLLAPSAR DISKS

By performing two-dimensional special relativistic (SR) magnetohydrodynamic simulations, we study possible signatures of gravitational waves (GWs) in the context of the collapsar model for long-duration gamma-ray bursts. In our SR simulations, the central black hole is treated as an absorbing boundary. By doing so, we focus on the GWs generated by asphericities in neutrino emission and matter motions in the vicinity of the hyperaccreting disks. We compute nine models by adding initial angular momenta and magnetic fields parametrically to a precollapse core of a $35 M_{\odot}$ progenitor star. As for the microphysics, a realistic equation of state is employed and the neutrino cooling is taken into account via a multiflavor neutrino leakage scheme. To accurately estimate GWs produced by anisotropic neutrino emission, we perform a ray-tracing analysis in general relativity by a post-processing procedure. By employing a stress formula that includes contributions both from magnetic fields and special relativistic corrections, we study also the effects of magnetic fields on the gravitational waveforms. We find that the GW amplitudes from anisotropic neutrino emission show a monotonic increase with time, whose amplitudes are much larger than those from matter motions of the accreting material. We show that the increasing trend of the neutrino GWs stems from the excess of neutrino emission in the direction near parallel to the spin axis illuminated from the hyperaccreting disks. We point out that a recently proposed future space-based interferometer like Fabry-Perot type DECIGO would permit the detection of these GW signals within $\approx$ 100 Mpc.

Parametrized 3D models of neutrino-driven supernova explosions

Time-dependent and direction-dependent neutrino and gravitational-wave (GW) signatures are presented for a set of 3D hydrodynamic models of parametrized, neutrino-driven supernova explosions of non-rotating 15 and 20 solar mass stars. We employ an approximate treatment of neutrino transport. Due to the excision of the high-density core of the proto-neutron star and the use of an axis-free overset grid, the models can be followed from the post-bounce accretion phase for more than one second without imposing any symmetry restrictions. GW and neutrino emission exhibit the generic time-dependent features known from 2D models. Non-radial hydrodynamic mass motions in the accretion layer and their interaction with the outer layers of the proto-neutron star together with anisotropic neutrino emission give rise to a GW signal with an amplitude of ~5-20 cm and frequencies 100--500 Hz. The GW emission from mass motions reaches a maximum before the explosion sets in. Afterwards the GW signal exhibits a low-frequency modulation, in some cases describing a quasi-monotonic growth, associated with the non-spherical expansion of the explosion shock wave and the large-scale anisotropy of the escaping neutrino flow. Variations of the mass-quadrupole moment due to convective activity inside the nascent neutron star contribute a high-frequency component to the GW signal during the post-explosion phase. The GW signals exhibit strong variability between the two polarizations, different explosion simulations and different observer directions, and does not possess any template character. The neutrino emission properties show fluctuations over the neutron star surface on spatial and temporal scales that reflect the different types of non-spherical mass motions. The modulation amplitudes of the measurable neutrino luminosities and mean energies are significantly smaller than predicted by 2D simulations.

Gravitational-wave signatures in successful vs. failed core-collapse supernovae

In this contribution, we discuss possible gravitational-wave (GWs) signatures emitted from core-collapse supernovae that do or do not produce explosions. For the former case, we study properties of GWs based on the three-dimensional (3D) supernova simulations, which demonstrate the neutrino-driven explosions aided by the standing accretion shock instability (SASI). By taking into account the effects of stellar rotation, we find that the gravitational waveforms from neutrinos in models that include rotation exhibit a common feature otherwise they vary much more stochastically in the absence of rotation. We point out that a recently proposed future space interferometers like Fabry-Perot type DECIGO would permit the detection of these signals for a Galactic supernova. For the black-hole forming supernovae, we study the GW emission based on a long-term special relativistic magnetohydrodynamic simulation in the light of collapsar model of long-duration gamma-ray bursts (GRBs). We find that the GWs from anisotropic neutrino emission illuminated by accretion disk become as high as the GWs contributed from matter motions of accreting material. These signals, possibly visible to the BBO-class detectors for a hundred Megaparsec distance scales, may give us an important probe into the central engines of GRBs.