Long-Term Multidimensional Models of Core-Collapse Supernovae: Progress and Challenges

Core-collapse supernovae (CCSNe) are among the most energetic explosions in the universe, liberating the prodigious amount of ~ 1053 erg, the binding energy of their compact remnants, neutron stars or stellar mass black holes. While 99% of this energy is emitted in neutrinos, 1% goes into the internal and asymptotic kinetic energy of the ejecta, and it is reasonable to assume that a tiny fraction is radiated in gravitational waves (GWs). Ever since the first experimental efforts to detect GWs, CCSNe have been considered prime sources of gravitational waves for interferometric detectors. Besides neutrinos, which have already been observed in the context of stellar core collapse of SN1987A, GWs could provide us access to the electromagnetically hidden compact inner core of some such cataclysmic events, supplying us for example with valuable information about the angular momentum distribution and the baryonic equation of state, both of which are uncertain. Furthermore, they might even help to constrain theoretically predicted SN mechanisms. However, GW astronomy strongly depends on the extensive data processing of the detector output on the basis of reliable GW estimates, which only recently have become feasible with the emerging power of supercomputers. The work presented in this thesis is concerned with numerical CCSN models and their imprints in GWs. I performed an extensive series of more than 30 three-dimensional magnetohydrodynamical (MHD) core-collapse simulations. My models are based on a 15M [...] progenitor stemming from stellar evolution calculations, an effective general relativistic potential and either the Lattimer-Swesty (with three possible compressibilities) or the Shen equation of state (EoS) for hot, dense matter. Furthermore, the neutrino transport is tracked by computationally efficient algorithms for the radiative transfer of massless fermions. I systematically investigated the effects of the microphysical finite-temperature nuclear EoS, the initial rotation rate, both the toroidal and the poloidal magnetic fields, and multidimensional gravitational potentials on the GW signature. Based on the results of these calculations, I obtained the largest – and also one of the most realistic – catalogue of GW signatures from 3D MHD stellar core collapse simulations at present. I stress the importance of including postbounce neutrino physics, since it quantitatively alters the GW signature. Non- and slowly-rotating models show GW emission caused by prompt and protoneutron star (PNS) convection. Moreover, the signal stemming from prompt convection allows for the distinction between the two different nuclear EoS indirectly by different properties of the fluid instabilities. For simulations with moderate or even fast rotation rates, I only find the axisymmetric type I wave signature at core bounce. In line with recent results, I could confirm that the maximum GW amplitude scales roughly linearly with the ratio of rotational to gravitational energy (T/|W|) at core bounce below a threshold value of about 10%. Furthermore, I point out that PNS can become dynamically unstable to rotational instabilities at T/|W| values as low as ~ 2% at core bounce. Apart from these two points, I show that it is generally very difficult to discern the effects of the individual features of the input physics in a GW signal from a rotating CCSN that can be attributed unambiguously to a specific model. Weak magnetic fields do not notably influence the dynamical evolution of the core and thus the GW emission. However, for strong initial poloidal magnetic fields ≥ 1012G, the combined action of flux-freezing and field winding leads to conditions where the ratio of magnetic field pressure to matter pressure reaches about unity which leads to the onset of a jet-like supernova explosion. The collimated bipolar out-stream of matter is then reflected in the emission of a type IV GW signal. In contradiction to axisymmetric simulations, I find evidence that nonaxisymmetric fluid modes can counteract or even suppress jet formation for models with strong initial toroidal magnetic fields. I emphasize the importance of including multidimensional gravitational potentials in rapidly rotating 3D CCSN simulations: taking them into account can alter the resulting GW amplitudes up to a factor of 2 compared to simulations which encounter gravity only by a monopolar approximation. Moreover, I show that the postbounce dynamics occuring in the outer layers (at radii R ≥ 200km) of models run with 3D gravity deviates vastly from the ones run with a 1D or 2D gravitational potential. The latter finding implies that both spherically symmetric and axisymmetric treatments of gravity are too restrictive for a quantitative description of the overall postbounce evolution of rapidly rotating CCSN models. The results of models with continued neutrino emission show that including deleptonization during the postbounce phase is an indispensable issue for the quantitative prediction of GWs from core-collapse supernovae, because it can alter the GW amplitude up to a factor of 10 compared to a pure hydrodynamical treatment. My collapse simulations indicate that corresponding events in our Galaxy would be detectable either by LIGO, if the source is rotating, or at least by the advanced LIGO detector, if it is not or only slowly rotating.

Core collapse supernovae (SN) are the final stages of stellar evolution in massive stars during which the central region collapses, forms a neutron star (NS) or black hole, and the outer layers are ejected. Recent explosion scenarios assume that the ejection is due to energy deposition by neutrinos into the envelope, but current models with detailed neutrino transport do not produce powerful explosions. There is new and mounting evidence for an asphericity and, in particular, for axial symmetry in several supernovae which may be hard to reconcile within the spherical picture. This evidence includes the observed high polarization and its variation with time, pulsar kicks, high velocity iron-group and intermediate-mass elements observed in remnants, and direct observations of the debris of SN 1987A. Some of the new evidence is discussed in more detail. To be in agreement with the observations, any successful mechanism must invoke some sort of axial symmetry for the explosion. Based on models in literature, we expect no such asymmetries from neutrino driven explosions.As a limiting case for aspherical explosions, we consider jet-induced/dominated explosions of “classical” core collapse supernovae. Bipolar outflows may be formed as a consequence of an accretion disk around the central object which is formed just after the core collapse, MHD mechanisms, or, maybe, some new instabilities within the neutrino picture. Our study is based on detailed 3-D hydrodynamical and radiation transport models. We demonstrate the influence of the jet properties and of the underlying progenitor structure on the final density and chemical structure. Our calculations show that low velocity, massive jets can explain the observations. Both asymmetric ionization and density/chemical distributions have been identified as crucial for the formation of asymmetric photospheres. Even within the picture of jet-induced explosion, the latter effect alone fails to explain early polarization in core collapse supernovae with a massive, hydrogen-rich envelope such as SN 1999em. The need for an asymmetric distribution of freshly formed 56Ni may lend additional support for the idea that the explosion mechanism itself is asymmetric. Solving neutrino transport is an important ‘component’ to solve the SN problem but, apparently, not the complete solution. A successful model has to include all the effects, i.e. the core bounce, neutrino transport, convective flows and, in addition, significant effects due to rotation and, maybe, magnetic fields. Finally, we discuss observational consequences and tests.KeywordsCore Collapse SupernovaThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

We use optical integral field spectroscopy (IFS) of nearby supernova (SN) host galaxies (0.005 <z< 0.03) provided by the Calar Alto Legacy Integral Field Area (CALIFA) Survey with the goal of finding correlations in the environmental parameters at the location of different SN types. In this first study of a series we focus on the properties related with star formation (SF). We recover the sequence in association of different SN types to the star-forming regions by using several indicators of the ongoing and recent SF related to both the ionized gas and the stellar populations. While the total ongoing SF is on average the same for the three SN types, SNe Ibc/IIb tend to occur closer to star-forming regions and in higher SF density locations than SNe II and SNe Ia; the latter shows the weakest correlation. SNe Ia host galaxies have masses that are on average ~0.3−0.8 dex higher than those of the core collapse (CC) SNe hosts because the SNe Ia hosts contain alarger fraction of old stellar populations. Using the recent SN Ia delay-time distribution and the SFHs of the galaxies, we show that the SN Ia hosts in our sample are expected to produce twice as many SNe Ia as the CC SN hosts. Since both types occur in hosts with a similar SF rate and hence similar CC SN rate, this can explain the mass difference between the SN Ia and CC SN hosts, and reinforces the finding that at least part of the SNe Ia originate from very old progenitors. By comparing the mean SFH of the eight least massive galaxies with that of the massive SF SN Ia hosts, we find that the low-mass galaxies formed their stars during a longer time (0.65%, 24.46%, and 74.89% in the intervals 0–0.42 Gyr, 0.42–2.4 Gyr, and >2.4 Gyr, respectively) than the massive SN Ia hosts (0.04%, 2.01%, and 97.95% in these intervals). We estimate that the low-mass galaxies produce ten times fewer SNe Ia and three times fewer CC SNe than the high-mass group. Therefore the ratio between the number of CC SNe and SNe Ia is expected to increase with decreasing galaxy mass. CC SNe tend to explode at positions with younger stellar populations than the galaxy average, but the galaxy properties at SNe Ia locations are one average the same as the global galaxy properties.

We present 3D full-sphere supernova simulations of non-rotating low-mass (∼9 M⊙) progenitors, covering the entire evolution from core collapse through bounce and shock revival, through shock breakout from the stellar surface, until fallback is completed several days later. We obtain low-energy explosions (∼0.5–1.0 × 1050 erg) of iron-core progenitors at the low-mass end of the core-collapse supernova (LMCCSN) domain and compare to a super-AGB (sAGB) progenitor with an oxygen–neon–magnesium core that collapses and explodes as electron-capture supernova (ECSN). The onset of the explosion in the LMCCSN models is modelled self-consistently using the vertex-prometheus code, whereas the ECSN explosion is modelled using parametric neutrino transport in the prometheus-HOTB code, choosing different explosion energies in the range of previous self-consistent models. The sAGB and LMCCSN progenitors that share structural similarities have almost spherical explosions with little metal mixing into the hydrogen envelope. A LMCCSN with less second dredge-up results in a highly asymmetric explosion. It shows efficient mixing and dramatic shock deceleration in the extended hydrogen envelope. Both properties allow fast nickel plumes to catch up with the shock, leading to extreme shock deformation and aspherical shock breakout. Fallback masses of $\mathord {\lesssim }\, 5\, \mathord {\times }\, 10^{-3}$ M⊙ have no significant effects on the neutron star (NS) masses and kicks. The anisotropic fallback carries considerable angular momentum, however, and determines the spin of the newly born NS. The LMCCSN model with less second dredge-up results in a hydrodynamic and neutrino-induced NS kick of &amp;gt;40 km s−1 and a NS spin period of ∼30 ms, both not largely different from those of the Crab pulsar at birth.

We present results from simulations of core-collapse supernovae in FLASH using a newly implemented multidimensional neutrino transport scheme and a newly implemented general relativistic (GR) treatment of gravity. We use a two-moment method with an analytic closure (so-called M1 transport) for the neutrino transport. This transport is multienergy, multispecies, velocity dependent, and truly multidimensional, i.e., we do not assume the commonly used “ray-by-ray” approximation. Our GR gravity is implemented in our Newtonian hydrodynamics simulations via an effective relativistic potential that closely reproduces the GR structure of neutron stars and has been shown to match GR simulations of core collapse quite well. In axisymmetry, we simulate core-collapse supernovae with four different progenitor models in both Newtonian and GR gravity. We find that the more compact proto–neutron star structure realized in simulations with GR gravity gives higher neutrino luminosities and higher neutrino energies. These differences in turn give higher neutrino heating rates (upward of ∼20%–30% over the corresponding Newtonian gravity simulations) that increase the efficacy of the neutrino mechanism. Three of the four models successfully explode in the simulations assuming GREP gravity. In our Newtonian gravity simulations, two of the four models explode, but at times much later than observed in our GR gravity simulations. Our results, in both Newtonian and GR gravity, compare well with several other studies in the literature. These results conclusively show that the approximation of Newtonian gravity for simulating the core-collapse supernova central engine is not acceptable. We also simulate four additional models in GR gravity to highlight the growing disparity between parameterized 1D models of core-collapse supernovae and the current generation of 2D models.

The formation of stellar black holes

Core-collapse supernovae (CCSN) mark the end of the life of massive stars and are cosmic laboratories for physics at the extremes. Numerical simulations of these explosions are essential to understanding the complex mechanisms that are involved. All four fundamental interactions have to be taken into account, which requires the combined knowledge of astrophysics, nuclear physics, particle physics, and observations. A key ingredient in simulations is the equation of state (EOS), which determines the contraction behavior of the proto-neutron star (PNS), and thus impacts neutrino energies and explosion dynamics. However, the EOS for hot and dense matter is still not fully understood and CCSN simulations rely on phenomenological EOS models that differ in their underlying theory as well as nuclear physics input. In this thesis, we investigate the impact of uncertainties in the EOS in CCSN simulations. Further, we present an extension of the high-density EOS models to lower densities and temperatures, which enables us to perform long-time simulations of CCSN, following the shock evolution up to several seconds after bounce. In the first part of this thesis, we present the first systematic study on the effect of different nuclear matter properties of the EOS in CCSN simulations. We investigate the impact of varying the nucleon effective mass, incompressibility, symmetry energy, and nuclear saturation point on the PNS contraction and its implication on the shock evolution. This allows us to examine possible reasons for differences in simulations with commonly used EOS models. We find that the contraction behavior of the PNS is mainly governed by the effective mass, which determines the thermal nucleonic contributions to the EOS. Larger effective masses result in smaller pressures at nuclear densities and a lower thermal index. This modifies the density, and thus the PNS contraction behavior, and consequently the shock propagation. We observe that variations in the symmetry energy impact the electron fraction, entropy, and temperature in the PNS interior. Our results suggest that differences among CCSN EOS mainly originate from their different nuclear matter properties. We verify that our models give reasonable modifications to the mass-radius relation of cold neutron stars and further investigate details of the explosion dynamics. Moreover, our EOS models are tested in different CCSN simulation codes, which yield similar results. Finally, we show that the choice of neutrino treatment impacts the PNS interior. In the second part, we perform long-time CCSN simulations that follow the shock evolution several seconds after bounce, which requires a large simulation domain. To this end, we present a formalism for a high-density EOS transition to lower densities and temperatures. This formalism is tested for various EOS models and different progenitors in spherical symmetry. Additionally, we verify its functionality in cylindrical symmetry and for several neutrino transport schemes. With the transition, we perform the first long-time CCSN simulations in FLASH for exploding models, following the shock expansion up to five seconds after bounce. Different CCSN scenarios are investigated, varying the rotational profile and the explosion energetics by enhancing the neutrino energy deposition in the neutrino leakage scheme. We find that additional rotation and heating favors neutrino-driven winds, which impacts the diagnostic energy. Our results indicate that rotation decreases the mass accretion and reduces neutrino luminosities, as suggested in previous studies. Moreover, the results are compared to simulations performed with an M1 neutrino transport scheme. This allows us to analyze differences in the electron fraction, which need to be considered for future nucleosynthesis studies.

Extreme temperatures and densities in core-collapse supernovae and one of their possible remnants, the so-called neutron stars, are likely to favor the appearance of new degrees of freedom such as hyperons and/or quark matter.&#13;\nThis work is dedicated to the investigation of the hadron-quark phase transition in core-collapse supernovae and cold neutron stars.&#13;\nTo this day, only a couple of supernova equations of state that consider quark matter have been developed and none of them fulfills the observational 2 M_sun neutron star mass constraint [...].&#13;\nThe phase transition from hadronic to quark matter can have an interesting impact on the post-bounce evolution of core-collapse supernovae: The phase transition is able to induce a collapse of the protoneutron star which ultimately can trigger an explosion, as shown in spherically-symmetric simulations [...]. So far, this scenario has not been investigated in multi-dimensional core-collapse supernova simulations.&#13;\n&#13;\nIn the first part of this work, we analyze cold hybrid stars (Hybrid stars are neutron stars that contain quark matter.) by the means of a systematic parameter scan for the phase transition properties. &#13;\nThe hadronic phase is described by the state-of-the-art supernova equation of state HS(DD2) and the quark phase by an equation of state with a constant speed of sound (CSS).&#13;\nChoosing a quark matter speed of sound of c_{QM}^2=1/3, we find promising cases which meet the 2 M_sun criterion and are interesting for core-collapse supernova explosions. We show that the very simple CSS equation of state is transferable into the well-known thermodynamic bag model, important for application in core-collapse simulations.&#13;\nAdditionally, the occurrence of reconfinement and multiple phase transitions is discussed. &#13;\nThe influence of hyperons in our parameter scan is studied as well. Including hyperons, no change in the general behavior is found, except for overall lower maximum masses. In both cases (with and without hyperons) we find that quark matter with c_{QM}^2=1/3 can increase the maximum mass only if reconfinement is suppressed or if quark matter is absolutely stable.&#13;\nThe systematic parameter study is completed with an analogous analysis using c_{QM}^2=1, the maximum value to be still consistent with special relativity. The higher speed of sound leads to more parameter configurations consistent with the 2 M_sun criterion. Increasing the speed of sound to c_{QM}^2&gt;1/3 is therefore an interesting case which increases the possibilities when constructing a future hybrid supernova equation of state.&#13;\n&#13;\nOn the basis of the best guess configuration obtained in the parameter scan for c_{QM}^2=1/3, we construct the new hybrid supernova equation of state BASQUARK. BASQUARK uses HS(DD2) for the hadronic part and a bag model to describe quark matter. The detailed analysis of BASQUARK with the sophisticated spherical supernova code AGILE-BOLTZTRAN shows an explosion for a 15 M_sun progenitor. Hence, BASQUARK is the first hybrid supernova equation of state that fulfills the 2 M_sun neutron star constraint and is known to trigger an explosion in spherical symmetry.&#13;\n&#13;\nThe second part of this work is dedicated to the analysis of BASQUARK in the 3D core-collapse supernova code ELEPHANT. To ensure an effective analysis at late post-bounce times without consuming a vast amount of computational resources, we develop a new method called the spherical restart method. This method allows us to perform a separate spherical AGILE-IDSA simulation, which is computationally very cheap, map its profile into ELEPHANT, and continue the simulation in three dimensions. The method shows that the obtained 3D profiles imitate well the profiles obtained in a consistently run simulation. &#13;\nIf the collapse behavior of ELEPHANT up to bounce is considered in AGILE-IDSA, the spherical restart method is able to reproduce profiles that are on spherical average almost identical to such, obtained in consistently run ELEPHANT simulations.&#13;\nThis allows the opportunity to increase the resolution for more detailed investigations.&#13;\n&#13;\nFinally, we apply BASQUARK in ELEPHANT and use a 15 M_sun and a 40 M_sun progenitor. Both progenitors explode in spherical symmetry due to the phase-transition induced collapse of the protoneutron star. &#13;\nIn initial tests, ab-intio calculations with ELEPHANT are executed with a low resolution of 2 km to proceed fast to the relevant post-bounce times.&#13;\nBoth progenitors ultimately explode due to oscillations of the protoneutron star which are probably an artifact of the low resolution. This mechanism is not expected at higher resolution. &#13;\nThe 15 M_sun progenitor does not show any indication of a collapse of the protoneutron star, but seems to be powered by the delayed-neutrino driven mechanism.&#13;\nIn turn, the 40 M_sun progenitor shows indications of a failed collapse of the protoneutron star.&#13;\nBy the use of the spherical restart method, the simulation is spherically restarted before the suspected collapse, using a resolution of 2 km, 1 km, and 500 m. &#13;\nThe 2 km run indicates once more collapse features, but fails due to stability issues caused by the low resolution. &#13;\nUsing a resolution of 1 km ultimately shows a collapse of the protoneutron star which results in the explosion of the star. 500 m resolution confirms the results using 1 km resolution and additionally helped the convection to develop. This is the first time, a phase-transition induced collapse and the succeeding explosion is simulated in a three-dimensional core-collapse supernova. We find that resolution is crucial for a correct description of quark matter in the center of the protoneutron star. In the near future, neutrino-quark rates and the IDSA treatment have to be investigated in more detail.&#13;\n&#13;\nThe results obtained with BASQUARK in ELEPHANT are preliminary yet. Nevertheless, this work opens the door into the new field of multi-dimensional core-collapse supernova simulations that consider quark matter and gives some clear indications on the subjects to be investigated in the future.&#13;\n

Neutrino transport in core collapse supernovae

The kinematics of black hole and neutron star X-ray binaries in the Galaxy should help to know their birth place and constrain their evolution. We have used multiple tools of modern astronomy to determine the trajectories in the Galaxy and track the origins of black hole and neutron star X-ray binaries that are of topical interest in astrophysics. We find three distinct classes of black hole and neutron star X-ray binaries: (1) low mass X-ray binaries that move at high velocities on galactocentric orbits similar to the most ancient stars born in the Galactic bulge and the halo, (2) those that move in the Galactic disk along paths that resemble the circular orbits of massive stars formed in the disk, and (3) high and intermediate mass X-ray binaries running away from their parent regions of star formation. Here we discuss some of the cases studied. The large transverse motions of neutron stars (NS's) in the plane of the sky are believed to result from kicks imparted in natal supernova (SN) explosions. SN explosions are usually invoked in models of the core collapse of massive stars onto black holes (BH's), but until present there have been few observations that can constrain the models of the physical processes by which stellar-mass black holes are formed. The velocity in three dimensions and the galactocentric orbit can be used to gain insight into this issue, tracking the compact object back to its birth place and constraining the energy of any putative natal kick. Compact microquasar jets are ubiquitous among accreting black holes and neutron stars, and their motion in the plane of the sky can be followed with high precision by astrometry at radio wavelengths with Very Long Baseline Interferometry (VLBI). The proper motion can also be determined by astrometry of the donor star at optical wavelengths. Optical and IR spectroscopy of the companion star provides the line of sight velocity of the system. Knowing the distance either from VLBI or from the properties of the donor star, the Galactic orbit of the X-ray binary can be computed using a Galactic potential model. Here we summarize the results of a series of papers on individual objects, on which we search for some new constrains to the physical models that describe the formation of stellar-mass black holes and neutron stars.

We investigate observable signatures of a first-order quantum chromodynamics (QCD) phase transition in the context of core-collapse supernovae. To this end, we conduct axially symmetric numerical relativity simulations with multi-energy neutrino transport, using a hadron–quark hybrid equation of state (EOS). We consider four nonrotating progenitor models, whose masses range from 9.6 to 70 M ⊙. We find that the two less-massive progenitor stars (9.6 and 11.2 M ⊙) show a successful explosion, which is driven by the neutrino heating. They do not undergo the QCD phase transition and leave behind a neutron star. As for the more massive progenitor stars (50 and 70 M ⊙), the proto-neutron star (PNS) core enters the phase transition region and experiences the second collapse. Because of a sudden stiffening of the EOS entering to the pure quark matter regime, a strong shock wave is formed and blows off the PNS envelope in the 50 M ⊙ model. Consequently the remnant becomes a quark core surrounded by hadronic matter, leading to the formation of the hybrid star. However, for the 70 M ⊙ model, the shock wave cannot overcome the continuous mass accretion and it readily becomes a black hole. We find that the neutrino and gravitational wave (GW) signals from supernova explosions driven by the hadron–quark phase transition are detectable for the present generation of neutrino and GW detectors. Furthermore, the analysis of the GW detector response reveals unique kHz signatures, which will allow us to distinguish this class of supernova explosions from failed and neutrino-driven explosions.

We perform a set of neutrino-driven core-collapse supernova (CCSN) simulations studying the hydrodynamical neutron star kick mechanism in three-dimensions. Our simulations produce neutron star (NS) kick velocities in a range between ~100-600 km/s resulting mainly from the anisotropic gravitational tug by the asymmetric mass distribution behind the supernova shock. This stochastic kick mechanism suggests that a NS kick velocity of more than 1000 km/s may as well be possible. An enhanced production of heavy elements in the direction roughly opposite to the NS recoil direction is also observed as a result of the asymmetric explosion. This large scale asymmetry might be detectable and can be used to constrain the NS kick mechanism.

The formation of stellar-mass black holes (BHs) is still very uncertain. Two main uncertainties are the amount of mass ejected in the supernova (SN) event (if any) and the magnitude of the natal kick (NK) the BH receives at birth (if any). Repetto et al., studying the position of Galactic X-ray binaries containing BHs, found evidence for BHs receiving high NKs at birth. In this paper, we extend that study, taking into account the previous binary evolution of the sources as well. The seven short-period BH X-ray binaries that we use are compact binaries consisting of a low-mass star orbiting a BH in a period less than 1 d. We trace their binary evolution backwards in time, from the current observed state of mass transfer, to the moment the BH was formed, and we add the extra information on the kinematics of the binaries. We find that several systems could be explained by no NK, just mass ejection, while for two systems (and possibly more) a high kick is required. So unless the latter have an alternative formation, such as within a globular cluster, we conclude that at least some BHs get high kicks. This challenges the standard picture that BH kicks would be scaled down from neutron star kicks. Furthermore, we find that five systems could have formed with a non-zero NK but zero mass ejected (i.e. no SN) at formation, as predicted by neutrino-driven NKs.

Context. As a result of their formation via massive single and binary stellar evolution, the masses of stellar-remnant black holes (BH) are subjects of great interest in this era of gravitational-wave detection from binary black hole (BBH) and binary neutron star merger events. Aims. In this work, we present new developments in the stellar-remnant formation and related schemes of the current N-body evolution program NBODY7. We demonstrate that the newly implemented stellar-wind and remnant-formation schemes in the stellar-evolutionary sector or BSE of the NBODY7 code, such as the “rapid” and the “delayed” supernova (SN) schemes along with an implementation of pulsational-pair-instability and pair-instability supernova (PPSN/PSN), now produce neutron star (NS) and BH masses that agree nearly perfectly, over large ranges of zero-age-main-sequence (ZAMS) mass and metallicity, with those from the widely recognised StarTrack population-synthesis program. We also demonstrate the new, recipe-based implementations of various widely debated mechanisms of natal kicks on NSs and BHs, such as “convection-asymmetry-driven”, “collapse-asymmetry-driven”, and “neutrino-emission-driven” kicks, in addition to a fully consistent implementation of the standard, fallback-dependent, momentum-conserving natal kick. Methods. All the above newly implemented schemes are also shared with the standalone versions of SSE and BSE. All these demonstrations are performed with both the updated standalone BSE and the updated NBODY7/BSE. Results. When convolved with stellar and primordial-binary populations as observed in young massive clusters, such remnant-formation and natal-kick mechanisms crucially determine the accumulated number, mass, and mass distribution of the BHs retained in young massive, open, and globular clusters (GCs); these BHs would eventually become available for long-term dynamical processing. Conclusions. Among other conclusions, we find that although the newer, delayed SN remnant formation model gives birth to the largest number (mass) of BHs, the older remnant-formation schemes cause the largest number (mass) of BHs to survive in clusters, when incorporating SN material fallback onto the BHs. The SN material fallback also causes the convection-asymmetry-driven SN kick to effectively retain similar numbers and masses of BHs in clusters as for the standard, momentum-conserving kick. The collapse-asymmetry-driven SN kick would cause nearly all BHs to be retained in clusters irrespective of their mass, remnant-formation model, and metallicity, whereas the inference of a large population of BHs in GCs would potentially rule out the neutrino-driven SN kick mechanism. Pre-SN mergers of massive primordial binaries would potentially cause BH masses to deviate from the theoretical, single-star ZAMS to mass-remnant mass relation unless a substantial of the total merging stellar mass of up to ≈40% is lost during a merger process. In particular, such mergers, at low metallicities, have the potential to produce low-spinning BHs within the PSN mass gap that can be retained in a stellar cluster and be available for subsequent dynamical interactions. As recent studies indicate, the new remnant-formation modelling reassures us that young massive and open clusters would potentially contribute to the dynamical BBH merger detection rate to a similar extent as their more massive GC counterparts.

Using a sample of 215 supernovae (SNe), we analyze their positions relative to the spiral arms of their host galaxies, distinguishing grand-design (GD) spirals from non-GD (NGD) galaxies. We find that: (1) in GD galaxies, an offset exists between the positions of Ia and core-collapse (CC) SNe relative to the peaks of arms, while in NGD galaxies the positions show no such shifts; (2) in GD galaxies, the positions of CC SNe relative to the peaks of arms are correlated with the radial distance from the galaxy nucleus. Inside (outside) the corotation radius, CC SNe are found closer to the inner (outer) edge. No such correlation is observed for SNe in NGD galaxies nor for SNe Ia in either galaxy class; (3) in GD galaxies, SNe Ibc occur closer to the leading edges of the arms than do SNe II, while in NGD galaxies they are more concentrated towards the peaks of arms. In both samples of hosts, the distributions of SNe Ia relative to the arms have broader wings. These observations suggest that shocks in spiral arms of GD galaxies trigger star formation in the leading edges of arms affecting the distributions of CC SNe (known to have short-lived progenitors). The closer locations of SNe Ibc vs. SNe II relative to the leading edges of the arms supports the belief that SNe Ibc have more massive progenitors. SNe Ia having less massive and older progenitors, have more time to drift away from the leading edge of the spiral arms.