We calculate the lightcurves of jet-driven bipolar core collapse supernova (CCSN) explosions into a bipolar circumstellar mater (CSM) and show that an equatorial observer finds the lightcurves to possess a rapid, and even an abrupt, drop. The scenario that might lead to such an explosion morphology is a common envelope evolution (CEE) where shortly before the CCSN explosion the RSG progenitor interacts with a more compact companion that spirals-in and spins-up the core. The companion can be a main sequence star, a neutron star, or a black hole. The binary interaction ejects a shell through an intensive wind and the CEE ejects a denser gas in the equatorial plane. We assume that the companion accretes mass and launches jets. We conduct three-dimensional (3D) hydrodynamical simulations where we launch weak jets, the shaping jets, into the dense shell and show that the interaction forms a bipolar CSM. As a result of the rapid pre-collapse core rotation jets drive the CCSN explosion. We simulate the interaction of the jets with the bipolar CSM and use a simple scheme to calculate the lightcurves. We show that the abrupt drop in the lightcurve of an observer not too close to the polar directions can account for the lightcurve of the hydrogen poor luminous supernova (LSN) SN 2018don. Our study strengthens the claim that jet-driven explosions account for many, even most, CCSNe.
Jens von der Linden, Clare Kimblin, Ian McKenna
et al.
Volcanic jet flows in explosive eruptions emit radio frequency signatures, indicative of their fluid dynamic and electrostatic conditions. The emissions originate from sparks supported by an electric field built up by the ejected charged volcanic particles. When shock-defined, low-pressure regions confine the sparks, the signatures may be limited to high-frequency content corresponding to the early components of the avalanche-streamer-leader hierarchy. Here, we image sparks and a standing shock together in a transient supersonic jet of micro-diamonds entrained in argon. Fluid dynamic and kinetic simulations of the experiment demonstrate that the observed sparks originate upstream of the standing shock. The sparks are initiated in the rarefaction region, and cut off at the shock, which would limit their radio frequency emissions to a tell-tale high-frequency regime. We show that sparks transmit an impression of the explosive flow, and open the way for novel instrumentation to diagnose currently inaccessible explosive phenomena.
We study by duality methods the extinction and explosion times of continuous-state branching processes with logistic competition (LCSBPs) and identify the local time at $\infty$ of the process when it is instantaneously reflected at $\infty$. The main idea is to introduce a certain "bidual" process $V$ of the LCSBP $Z$. The latter is the Siegmund dual process of the process $U$, that was introduced in Foucart (2019), as the Laplace dual of $Z$. By using both dualities, we shall relate local explosions and the extinction of $Z$ to local extinctions and the explosion of the process $V$. The process $V$ being a one-dimensional diffusion on $[0,\infty]$, many results on diffusions can be used and transfered to $Z$. A concise study of Siegmund duality for one-dimensional diffusions and their boundaries is also provided.
Pedro Ruben Rivera-Ortiz, Ary Rodríguez-González, Jorge Cantó
et al.
During the fragmentation and collapse of a molecular cloud, it is expected to have close encounters between (proto)stellar objects that can lead to the ejection of a fraction of them as runaway objects. However, the duration and the consequences of such encounters perhaps are small such that there is no direct evidence of their occurrence. As a first approximation, in this work, we analytically analyze the interaction of a massive object that moves at high velocity into a cluster of negligible mass particles with an initial number density distribution $\propto R^{-α}$. We have found that the runaway conditions of the distribution after the encounter are related to the mass and the velocity of the star and the impact parameter of each particle to the stellar object. Then, the cluster particles are gravitationally accelerated by the external approaching star, destroying the cluster and the dispersion and velocities of the particles have explosive characteristics. We compare this analytical model with several numerical simulations and finally, we applied our results to the Orion Fingers in the Orion BN/KL region, which show an explosive outflow that could be triggered by the gravitational interaction of several (proto)stellar objects.
A model has been proposed for estimation of plasma parameters of explosive electron emission pulses in vacuum arc discharge. It based on transition through the critical state during the explosion and allow to predict the cathode spot plasma parameters for various materials. The cathode flare plasma ions kinetic energy was estimated to be of about 100 times critical temperature. Average ions charge has been estimated as (1 + critical temperature value in eV). Both dependencies agree with experimental results. Explosive electron emission plasma momentum per transferred charge has been evaluated to be about tens of g cm / (s C) and agrees with the product of measured ions velocity and erosion rate. Effective critical temperature approach has been proposed for the estimation of plasma properties for the arc burning at surface with a fine structure
V. M. Romanova, G. V. Ivanenkov, E. V. Parkevich
et al.
This paper presents the results of studying of dispersed media formation during the electrical explosion of thin metal wires in vacuum by using low-current generators ($\sim 1$-$10$~kA). Particular attention is paid to the analysis of the composition and structure of the corresponding explosion products as well as to the problem of their visualization using simultaneous laser interferometry and shadow imaging at two wavelengths (1.064~$μ$m and 0.532~$μ$m). Our findings point to the fact that the important role in the visualization of the explosion products belongs to multiple scattering by submicron droplets of dense condensed matter, which are mixed with metal vapor. The hypothesis on the existence of submicron droplets in the products of exploding metal wires correlates with the results obtained by soft x-ray radiography combined with a laser probing technique. Taking into account the multiple scattering by submicron droplets, it is possible to significantly clarify the parameters of the explosion products visualized via laser probing techniques as well as to gain a deeper insight into the physics behind the electrical wire explosion.
Anticipating the generation of high velocity debris from shock-loaded specimens and the damage that their impacts may cause to nearby equipment is a major safety issue in applications involving shock waves, such as pyrotechnics [1] or inertial confinement fusion (ICF) experiments on large scale laser facilities [2]. Microjetting is one of the processes governing such debris generation. It is due to the interaction of a shock wave with a free surface presenting geometrical defects such as pits, cavities, scratches, or grooves, leading to material ejection from these defects, in the form of thin jets expanding ahead of the main surface and breaking up into small particles [3]. Over the last few years, we have used laser shock loading in order to expand microjetting investigations over ranges of small spatial scales (μm scale), extremely high loading rates (~ 107 s-1) and very short pressure pulses (a few ns) [4-11]. Optical shadowgraphy and Photonic Doppler Velocimetry (PDV) have been used to measure both jet tip and planar surface velocities [4-6], while attempts to infer fragments size distributions, to be compared with model predictions, have been made using either fast transverse shadowgraphy [7] or ejecta recovery [8]. More recently, picosecond x-ray radiography has been used to provide estimates of the density gradients along the jets and of the total ejected mass at different times after shock breakout [9-11]. Here, we present the development of a new picosecond laser imaging diagnostic intended to overcome the limitations of our current transverse optical shadowgraphy setup. We describe our experimental setup and show the results of our first experiments performed using both visible (532 nm) and UV (355 nm) lightning of the sample. These results are compared to those obtained at LANL under high explosive loading using ultraviolet in-line Fraunhofer holography [12], and also to molecular dynamics (MD) simulations performed by our colleagues at lower space and time scales [15-18].
Magnetic reconnection is thought to be a key process in most of solar eruptions. Thanks to high-resolution observations and simulations, the studied scale of reconnection process has become smaller and smaller. Spectroscopic observations show that the reconnection site can be very small, which always exhibits a bright core and two extended wings with fast speeds, i.e., transition-region explosive events. In this paper, using the PLUTO code, we perform a 2-D magnetohydrodynamic simulation to investigate the small-scale reconnection in double current sheets. Based on our simulation results, such as the line-of-sight velocity, number density and plasma temperature, we can synthesize the line profile of Si IV 1402.77 A which is a well known emission line to study the transition-region explosive events on the Sun. The synthetic line profile of Si IV 1402.77 A is complex with a bright core and two broad wings which can extend to be nearly 200 km/s. Our simulation results suggest that the transition-region explosive events on the Sun are produced by plasmoid instability during the small-scale magnetic reconnection.
The question why and how core-collapse supernovae (SNe) explode is one of the central and most long-standing riddles of stellar astrophysics. A solution is crucial for deciphering the SN phenomenon, for predicting observable signals such as light curves and spectra, nucleosynthesis, neutrinos, and gravitational waves, for defining the role of SNe in the evolution of galaxies, and for explaining the birth conditions and properties of neutron stars (NSs) and stellar-mass black holes. Since the formation of such compact remnants releases over hundred times more energy in neutrinos than the SN in the explosion, neutrinos can be the decisive agents for powering the SN outburst. According to the standard paradigm of the neutrino-driven mechanism, the energy transfer by the intense neutrino flux to the medium behind the stagnating core-bounce shock, assisted by violent hydrodynamic mass motions (sometimes subsumed by the term "turbulence"), revives the outward shock motion and thus initiates the SN blast. Because of the weak coupling of neutrinos in the region of this energy deposition, detailed, multidimensional hydrodynamic models including neutrino transport and a wide variety of physics are needed to assess the viability of the mechanism. Owing to advanced numerical codes and increasing supercomputer power, considerable progress has been achieved in our understanding of the physical processes that have to act in concert for the success of neutrino-driven explosions. First studies begin to reveal observational implications and avenues to test the theoretical picture by data from individual SNe and SN remnants but also from population-integrated observables. While models will be further refined, a real breakthrough is expected through the next Galactic core-collapse SN, when neutrinos and gravitational waves can be used to probe the conditions deep inside the dying star. (abridged)
Anthony Mezzacappa, Eric J. Lentz, Stephen W. Bruenn
et al.
We present results from an ab initio three-dimensional, multi-physics core collapse supernova simulation for the case of a 15 M progenitor. Our simulation includes multi-frequency neutrino transport with state-of-the-art neutrino interactions in the "ray-by-ray" approximation, and approximate general relativity. Our model exhibits a neutrino-driven explosion. The shock radius begins an outward trajectory at approximately 275 ms after bounce, giving the first indication of a developing explosion in the model. The onset of this shock expansion is delayed relative to our two-dimensional counterpart model, which begins at approximately 200 ms after core bounce. At a time of 441 ms after bounce, the angle-averaged shock radius in our three-dimensional model has reached 751 km. Further quantitative analysis of the outcomes in this model must await further development of the post-bounce dynamics and a simulation that will extend well beyond 1 s after stellar core bounce, based on the results for the same progenitor in the context of our two-dimensional, counterpart model. This more complete analysis will determine whether or not the explosion is robust and whether or not observables such as the explosion energy, 56Ni mass, etc. are in agreement with observations. Nonetheless, the onset of explosion in our ab initio three-dimensional multi-physics model with multi-frequency neutrino transport and general relativity is encouraging.
R. A. da Costa, S. N. Dorogovtsev, A. V. Goltsev
et al.
In a new type of percolation phase transition, which was observed in a set of non-equilibrium models, each new connection between vertices is chosen from a number of possibilities by an Achlioptas-like algorithm. This causes preferential merging of small components and delays the emergence of the percolation cluster. First simulations led to a conclusion that a percolation cluster in this irreversible process is born discontinuously, by a discontinuous phase transition, which results in the term "explosive percolation transition". We have shown that this transition is actually continuous (second-order) though with an anomalously small critical exponent of the percolation cluster. Here we propose an efficient numerical method enabling us to find the critical exponents and other characteristics of this second order transition for a representative set of explosive percolation models with different number of choices. The method is based on gluing together the numerical solutions of evolution equations for the cluster size distribution and power-law asymptotics. For each of the models, with high precision, we obtain critical exponents and the critical point.
We show that turbulence in core collapse supernovae (CCSNe) which has been shown recently to ease shock revival might also lead to the formation of intermittent thick accretion disks, or accretion belts, around the newly born neutron star (NS). The accretion morphology is such that two low density funnels are formed along the polar directions. The disks then are likely to launch jets with a varying axis direction, i.e., jittering-jets, through the two opposite funnels. The energy contribution of jets in this jittering jets mechanism might result in an explosion energy of E>10^51erg, even without reviving the stalled shock. We strengthen the jittering jets mechanism as a possible explosion mechanism of CCSNe.
Stephen W. Bruenn, Eric J. Lentz, W. Raphael Hix
et al.
We present four ab initio axisymmetric core-collapse supernova simulations for 12, 15, 20, and 25 $M_\odot$ progenitors. All of the simulations yield explosions and have been evolved for at least 1.2 seconds after core bounce and 1 second after material first becomes unbound. Simulations were computed with our Chimera code employing spectral neutrino transport, special and general relativistic transport effects, and state-of-the-art neutrino interactions. Continuing the evolution beyond 1 second allows explosions to develop more fully and the processes powering the explosions to become more clearly evident. We compute explosion energy estimates, including the binding energy of the stellar envelope outside the shock, of 0.34, 0.88, 0.38, and 0.70 B ($10^{51}$ ergs) and increasing at 0.03, 0.15, 0.19, and 0.52 B s$^{-1}$, respectively, for the 12, 15, 20, and 25 $M_\odot$ models. Three models developed pronounced prolate shock morphologies, while the 20 $M_\odot$ model, though exhibiting lobes and accretion streams like the other models, develops an approximately spherical, off-center shock as the explosion begins and then becomes moderately prolate $\sim$600 ms after bounce. This reduces the explosion energy relative to the other models by reducing mass accretion during the critical explosion power-up phase. We examine the growth of the explosion energy in our models through detailed analyses of the energy sources and flows. We find that the 12 and 20 $M_\odot$ models have explosion energies comparable to that of the lower range of observed explosion energies while the 15 and 25 $M_\odot$ models are within the range of observed explosion energies, particularly considering the rate at which their explosion energies are increasing. The ejected $^{56}$Ni masses given by our models are all within observational limits as are the proto-neutron star masses and kick velocities. (Truncated)