Outgoing Shock Research Articles

Monster Shocks, Gamma-Ray Bursts, and Black Hole Quasi-normal Modes from Neutron-star Collapse

We perform the first magnetohydrodynamic simulation tracking the magnetosphere of a collapsing magnetar. The collapse is expected for massive rotating magnetars formed in merger events and may occur many hours after the merger. Our simulation suggests a novel mechanism for a gamma-ray burst (GRB), which is uncollimated and forms a delayed high-energy counterpart of the merger gravitational waves. The simulation shows that the collapse launches an outgoing magnetospheric shock, and a hot magnetized outflow forms behind the shock. The outflow is baryon free and uncollimated, and its power peaks on a millisecond timescale. Then, the outflow becomes modulated by the ring-down of the nascent black hole, imprinting its kilohertz quasi-normal modes on the GRB tail.

On the critical exponent pc of the 3D quasilinear wave equation [formula omitted] with short pulse initial data. I, global existence

For the 3D quasilinear wave equation −(1+(∂tϕ)p)∂t2ϕ+Δϕ=0 with the short pulse initial data (ϕ,∂tϕ)(1,x)=(δ2−ε0ϕ0(r−1δ,ω),δ1−ε0ϕ1(r−1δ,ω)), where p∈N, p≥2, 0<ε0<1, r=|x|, ω=xr∈S2, and δ>0 is sufficiently small, under the outgoing constraint condition (∂t+∂r)kϕ(1,x)=O(δ2−ε0−kmax⁡{0,1−(1−ε0)p}) for k=1,2, we will establish the global existence of smooth large data solution ϕ when p>pc with pc=11−ε0 being the critical exponent. In the forthcoming paper, when 1≤p≤pc, we show the formation of the outgoing shock before the time t=2 under the same outgoing constraint condition and the other suitable assumption of (ϕ0,ϕ1).

Oblique shock wave in turbulent flow

Abstract The main attention is paid to the analytical analysis of an oblique shock wave in a turbulent adiabatic gas flow. For this purpose, a modified Rankine–Hugoniot model was obtained. On its basis, a solution was derived for the Rankine–Hugoniot conditions for a gas flow with various degrees of turbulence, as well as the equation of the modified Hugoniot adiabat. The behavior of the velocity of an adiabatic turbulent gas flow during its passage through an oblique shock wave at different levels of turbulence is demonstrated. A modification of Prandtl’s law for the velocity coefficients was obtained. The shock polar was also analyzed. The relationship between the angular gas flow and the angle of the shock wave was derived. Finally, the condition for the appearance of an outgoing bow shock wave was obtained.

Fate of quantum black holes

We study the quantum dynamics of the Lema\^{\i}tre-Tolman-Bondi space-times using a polymer quantization prescription based on loop quantum cosmology that incorporates fundamental discreteness. By solving an effective equation derived from this quantization, we find analytical solutions for the Oppenheimer-Snyder and thin-shell collapse models, and numerical solutions for a variety of asymptotically flat collapsing dust profiles. Our study (i) tracks the formation, evolution, and disappearance of dynamical horizons, (ii) shows that matter undergoes a nonsingular bounce that results in an outgoing shock wave, (iii) determines black hole lifetime to be proportional to the square of its mass, and (iv) provides a conformal diagram that substantially modifies the standard ``information loss'' picture by resolving the singularity and replacing the event horizon by transient apparent horizons.

Numerical Modeling of Propagation of an Outgoing Shock Wave Produced at Cavitation Bubble Collapse

Numerical Modeling of Propagation of an Outgoing Shock Wave Produced at Cavitation Bubble Collapse

Quantum Gravity of Dust Collapse: Shock Waves from Black Holes.

We study the quantum gravitational collapse of spherically symmetric pressureless dust. Using an effective equation derived from a polymer quantization in the connection-triad phase space variables of general relativity, we find numerically, for a variety of initial dust configurations, that (i)trapped surfaces form and disappear as an initially collapsing density profile evolves into an outgoing shock wave; (ii)black hole lifetime is proportional to the square of its mass; and (iii)there is no mass inflation at inner apparent horizons. These results provide a substantially different view of black hole formation and subsequent evolution than found from semiclassical analyses.

Spatiotemporal characterization of the laser-induced plasma plume in simulated Martian conditions

With ChemCam on NASA's Curiosity rover, SuperCam on NASA's Perseverance rover, and MarSCoDe on the Zhurong rover of the China National Space Administration, there are currently three instruments on Mars that employ laser-induced breakdown spectroscopy (LIBS) to analyze the chemical composition of Martian rocks and soils. With more than 880,000 LIBS measurements on Mars by ChemCam alone, the LIBS technique has been proven to be uniquely qualified for the in-situ robotic exploration of planetary surfaces. Since the laser-induced plasma exhibits a complex spatiotemporal evolution that has a significant impact on the recorded LIBS spectra, fundamental investigations of the plasma propagation and the spatial distributions of the plasma emissions can provide important insight that can help to improve the analysis of Martian LIBS spectra. Here we present first results from our LIBS plasma imaging setup, which allows us to spatially and temporally resolve the spectral emissions from the laser-induced plasma in simulated Martian atmospheric conditions. Investigating a calcium sulfate sample, we find that the commonly applied assumption of a nearly isothermal and homogeneous plasma with a colder outer layer is not sufficient to describe the laser-induced plasma on Mars. Instead, different spectral features show unique spatial distributions that suggest a strong influence of the outgoing shock wave. After plasma formation, the plasma center is found to rapidly become colder and more rarefied than the outer plasma regions. Molecular emissions are found to originate in this cold plasma center.

Primordial black holes from the QCD epoch: linking dark matter, baryogenesis, and anthropic selection

ABSTRACT If primordial black holes (PBHs) formed at the quark-hadron epoch, their mass must be close to the Chandrasekhar limit, this also being the characteristic mass of stars. If they provide the dark matter (DM), the collapse fraction must be of order the cosmological baryon-to-photon ratio ∼10−9, which suggests a scenario in which a baryon asymmetry is produced efficiently in the outgoing shock around each PBH and then propagates to the rest of the Universe. We suggest that the temperature increase in the shock provides the ingredients for hotspot electroweak baryogenesis. This also explains why baryons and DM have comparable densities, the precise ratio depending on the size of the PBH relative to the cosmological horizon at formation. The observed value of the collapse fraction and baryon asymmetry depends on the amplitude of the curvature fluctuations that generate the PBHs and may be explained by an anthropic selection effect associated with the existence of galaxies. We propose a scenario in which the quantum fluctuations of a light stochastic spectator field during inflation generate large curvature fluctuations in some regions, with the stochasticity of this field providing the basis for the required selection. Finally, we identify several observational predictions of our scenario that should be testable within the next few years. In particular, the PBH mass function could extend to sufficiently high masses to explain the black hole coalescences observed by LIGO/Virgo.

A Massive Star’s Dying Breaths: Pulsating Red Supergiants and Their Resulting Type IIP Supernovae

Abstract Massive stars undergo fundamental mode and first overtone radial pulsations with periods of 100–1000 days as red supergiants (RSGs). At large amplitudes, these pulsations substantially modify the outer envelope’s density structure encountered by the outgoing shock wave from the eventual core collapse of these stars. Using Modules for Experiments in Stellar Astrophysics (MESA), we model the effects of fundamental mode and first overtone pulsations in the RSG envelopes and the resulting Type IIP supernovae (SNe) using MESA+STELLA. We find that, in the case of fundamental mode pulsations, SN plateau observables, such as the luminosity at day 50, L 50; time-integrated shock energy, ET; and plateau duration, t p, are consistent with radial scalings derived considering explosions of nonpulsating stars. Namely, most of the effect of the pulsation is consistent with the behavior expected for a star of a different size at the time of explosion. However, in the case of overtone pulsations, the Lagrangian displacement is not monotonic. Therefore, in such cases, excessively bright or faint SN emission at different times reflects the underdense or overdense structure of the emitting region near the SN photosphere.

Non-equilibrium steady states in quantum critical systems with Lifshitz scaling

We study out-of-equilibrium energy transport in a quantum critical fluid with Lifshitz scaling symmetry following a local quench between two semi-infinite fluid reservoirs. The late time energy flow is universal and is accommodated via a steady state occupying an expanding central region between outgoing shock and rarefaction waves. We consider the admissibility and entropy conditions for the formation of such a non-equilibrium steady state for a general dynamical critical exponent z in arbitrary dimensions and solve the associated Riemann problem. The Lifshitz fluid with z = 2 can be obtained from a Galilean boost invariant field theory and the non-equilibrium steady state is identified as a boosted thermal state. A Lifshitz fluid with generic z is scale invariant but without boost symmetry and in this case the non-equilibrium steady state is genuinely non-thermal.

Asymptotic stability of the viscous shock wave for the one-dimensional compressible Navier–Stokes equations with density dependent viscous coefficient on the half space

In this paper, taking the boundary effect into consideration, we investigate the asymptotic stability of a viscous shock wave for one-dimensional isentropic compressible Navier–Stokes equations with density dependent viscous coefficient. Under the assumption that the viscous coefficient is given as a power function of the density, we prove that, for any positive power index of the viscous coefficient, if the amplitude of the corresponding outgoing viscous shock wave is suitably small and the initial data are close to the outgoing viscous shock wave which is far from the boundary, then a global solution exists uniquely in time and tends towards the properly shifted viscous shock wave as the time goes to infinity. The proof is given by an elementary energy method.

Bombardment history of asteroid 4 Vesta recorded by brecciated eucrites: Large impact event clusters at 4.50 Ga and discreet bombardment until 3.47 Ga

Abstract The thermal/impact histories of sixteen eucrite meteorites were investigated: three monomict eucrites (NWA 999, A-87272,87, and Stannern), five polymict eucrites (NWA 1000, NWA 1666, NWA 5601, Y-980066,100, and Y-980255,100), three quench-textured, eucrite melt rocks (Y-981646,21, Y-981651,105, and MIL 0766214), one eucrite dominantly comprised of quench-textured clasts (QUE 99005,11), three unclassified eucrite breccias (LAP 031316,9, LAR 06870,5, QUE 99799,4) and one unbrecciated eucrite (EET 92004,17), included here due to its shock features. We have measured fifteen high-precision new 40 Ar/ 39 Ar plateau ages on plagioclase and matrix for ten of these meteorites with a tight cluster of nine ages obtained from three different polymict breccias. These ages range from 4534 ± 56 Ma to 4491 ± 16 Ma resulting in a concordant age population ( P = 0.16). The fact that such a cluster of ages is recorded in unrelated breccias which are made of a priori unrelated components, leads us to propose that those ages recorded a single heating event on a large scale, and is interpreted here as a high-energy impact event, early in the history of Vesta at 4500 ± 4 Ma. We propose that the debris was ejected and isolated from subsequent large impacts in a secondary rubble pile asteroid where the energy of the outgoing shock wave from an impact is significantly reduced as it compacts the target material ( Holsapple et al., 2002 , and references therein) . The other analyses define a spread of five plateau ages ranging from 3851± 21 Ma to 3469 ± 35 Ma, over ∼380 Ma. An additional apparent plateau age of 4288 ± 38 Ma, but with a diffusion profile of cumulative 39 Ar release, along with published U-Pb apatite age of ∼4.14 Ga, suggests that the data might either define a true continuum (normal background bombardment) from 4.5 Ga to 3.47 Ga or cluster between ∼3.85 Ga and ∼3.47 Ga (excavation of a fresh surface at 3.85 Ga continuously bombarded until 3.47 Ga). Both scenarios are compatible with a final ejection age of 3.47 Ga when a major impact liberates the bulk of the brecciated meteorites into another secondary rubble pile asteroid, where the brecciated eucrites stayed relatively well protected from subsequent major impacts. Based on these results and recent crater counting measurements, we propose that the excavation and bulk ejection were caused by the Rheasilvia (ca. 3.47 Ga) basin-forming impact. Diffusion models on plagioclase crystals with different Ar age spectrum signatures, from a single breccia (NWA1666; 4501 ± 7 Ma), suggest that either: (1) the formation of the breccia is very young, or (2) different plagioclase crystals have different diffusion characteristics, and/or (3) the porosity caused heterogeneous temperatures during an impact heating event, particularly likely if the 4.5 Ga brecciated eucrites were stored in a rubble pile asteroid. Many or possibly most large asteroids being re-accumulated rubble piles with potential large porosity ( Holsapple et al., 2002 ). Scenarios (2) and (3) preclude the usage of multi-grain aliquots to decipher the time-temperature history of most impact breccia using 40 Ar/ 39 Ar thermochronology.

GEOMETRY ANALYSIS OF SUPERSONIC FLOW AROUND TWO AXIALLY SYMMETRICAL BODIES USING THE DIGITAL IMAGE PROCESSING METHOD

The scientific paper covers the research of the geometric laws of the intersection of two angle shock waves formed upon supersonic flow with zero incidence of two bodies. The positions of shock waves engaging with the surfaces of the models of axially symmetrical bodies are determined. Systems of analysis and decision support are based on the involvement of photographs (video frames) processing results by the image intensity parameter. This method facilitates the identification of the shock wave angle with a higher rate of probability, and, therefore, the more precise definition of the engagement points of the shock wave with the researched surface. This paper analyses the video frames of the interaction of shock waves using the digital image processing method by the image intensity parameter, the formulas determining the intersection point of shock waves, that occur upon the supersonic motion of two axially symmetric bodies near each other, are determined. The positions of the point of contact of the outgoing shock wave with the surface of the second object were determined, factoring in the difference in the the incoming and outgoing shock wave angles. The availability of sufficient statistics allowed to identify theoretical relationships between the gas flow rate, the geometric parameters of objects, the distances between them, density, pressure and image intensity in photographs. The method of digital image processing can be applied to the analysis of shock waves during the flow around a supersonic stream of bodies with a "blunt" end. The shock wave front in this case is described by a secondorder curve, upon the analysis of which it is necessary to select a portion of this curve, replacing it with some accuracy by a straight line segment (Mach line).

Development of a Matlab Code for Plane Wave Lens and its Validation by Autodyn-2D

Plane wave generator is normally composed of two explosives having dissimilar detonation velocity. It is used for directing the spherically outgoing shock wave front to a planar form. Plane wave generators are utilized to find material behavior under dynamic loading. This paper presents the shock arrival time for two plane wave generators by developed Matlab code and its comparison with Ansys Autodyn. The diameter of both plane wave generators is kept the same. One plane wave generator is composed of Octogen and Barium Nitrate and the other is composed of Octogen and Tri Nitro Toluene. Obtained results were surprisingly in agreement. Maximum and minimum obtained flatness for the plane wave were ±0.56 and ±0.08ms respectively within the whole diameter of the plane wave generator. The developed code can be utilized to find the profile of a plane wave generator, minimizing the time and cost many times.

Twin radio relics in the nearby low-mass galaxy cluster Abell 168

We report the discovery of twin radio relics in the outskirts of the low-mass merging galaxy cluster Abell 168 (redshift=0.045). One of the relics is elongated with a linear extent $\sim$ 800 kpc, a projected width of $\sim$ 80 kpc and is located $\sim$ 900 kpc toward the north of the cluster center, oriented roughly perpendicular to the major axis of the X-ray emission. The second relic is ring-shaped with a size $\sim$ 220 kpc and is located near the inner edge of the elongated relic at a distance of $\sim$ 600 kpc from the cluster center. These radio sources were imaged at 323 and 608 MHz with the Giant Meterwave Radio Telescope and at 1520 MHz with the Karl G Jansky Very Large Array (VLA). The elongated relic was detected at all the frequencies with a radio power at 1.4 GHz of 1.38$\pm 0.14 \times 10^{23}$ W Hz$^{-1}$ having a power law in the frequency range 70 - 1500 MHz (S$\propto \nu^{\alpha}, \alpha = -1.1 \pm 0.04$). This radio power is in good agreement with that expected from the known empirical relation between the radio powers of relics and the host cluster masses. This is the lowest mass (M$_{500}$ = 1.24$\times$10$^{14}$ M$_{o}$) cluster in which relics due to merger shocks are detected. The ring-shaped relic has a steeper spectral index ($\alpha$) of -1.74$\pm$0.29 in the frequency range 100 - 600 MHz. We propose this relic to be an old plasma revived due to adiabatic compression by the outgoing shock which produced the elongated relic.

Impacts into porous asteroids

Many small bodies in the solar system have bulk density well below the solid density of the constituent mineral grains in their meteorite counterparts. Those low-density bodies undoubtedly have significant porosity, which is a key factor that affects the formation of impact craters. This paper summarizes the results of lab experiments in which materials with porosity ranging from 43% to 96% were impacted at ∼1800 m/s. The experiments were performed on a geotechnical centrifuge, in order to reproduce the lithostatic overburden stress and ejecta ballistics that occur in large-scale cratering events on asteroids or planetary satellites. Experiments performed at various accelerations, up to 514G, simulate the outcomes of impacts at size scales up to several tens of km in diameter.Our experiments show that an impact into a highly porous cohesionless material generates a large ovoid-shaped cavity, due to crushing by the outgoing shock. The cavity opens up to form a transient crater that grows until the material flow is arrested by gravity. The cavity then collapses to form the final crater. During collapse, finely crushed material that lines the cavity wall is carried down and collected in a localized region below the final crater floor. At large simulated sizes (high accelerations), most of the crater volume is formed by compaction, because growth of the transient crater is quickly arrested. Nearly all ejected material falls back into the crater, leaving the crater without an ejecta blanket. We find that such compaction cratering and suppression of the ejecta blankets occur for large craters on porous bodies when the ratio of the lithostatic stress at one crater depth to the crush strength of the target exceeds ∼0.005. The results are used to identify small solar system bodies on which compaction cratering likely occurs. A model is developed that gives the crater size and ejecta mass that would result for a specified impact into a porous object.

Arbitrary interaction of plane supersonic flows

Subject of study.We consider the Riemann problem for parameters at collision of two plane flows at a certain angle. The problem is solved in the exact statement. Most cases of interference, both stationary and non-stationary gas-dynamic discontinuities, followed by supersonic flows can be reduced to the problem of random interaction of two supersonic flows. Depending on the ratio of the parameters in the flows, outgoing discontinuities turn out to be shock waves, or rarefactionwaves. In some cases, there is no solution at all. It is important to know how to find the domain of existence for the relevant decisions, as the type of shock-wave structures in these domains is known in advance. The Riemann problem is used in numerical methods such as the method of Godunov. As a rule, approximate solution is used, known as the Osher solution, but for a number of problems with a high precision required, solution of this problem needs to be in the exact statement. Main results.Domains of existence for solutions with different types of shock-wave structure have been considered. Boundaries of existence for solutions with two outgoing shock waves are analytically defined, as well as with the outgoing shock wave and rarefaction wave. We identify the area of Mach numbers and angles at which the flows interact and there is no solution. Specific flows with two outgoing rarefaction waves are not considered. Practical significance. The results supplement interference theory of stationary gas-dynamic discontinuities and can be used to develop new methods of numerical calculation with extraction of discontinuities.

A possible mechanism for the formation of humps in the orbital light curves of WZ Sge cataclysmic variable stars

A mechanism for the formation of humps in the light curves of WZ Sge cataclysmic variables is proposed, based on the results of three-dimensional simulations of the gas dynamics in the V455 And system. Analysis of the computed flow structure shows the formation of an accretion disk and four shocks in the system, located at the outer edge of the disk. Moreover, a precessional spiral density wave forms in the accretion disk, which is essentially at rest in the observer’s frame. As a consequence, all four shocks (two arms of a tidal shock, a “hot line,” and an outgoing shock) pass through the location of the precessional density wave during each rotation of the disk. The interaction of the precessional spiral density wave with the shocks leads to an additional local density enhancement in the vicinity of the shocks. This strengthens the shocks and enhances the energy release at the shock fronts; this, in turn, should increase the brightness of the system, which could be observed as a hump in the light curve. The shift of the humps observed in the V455 And light curve in orbital phase as a function of the observing epoch is easy to explain in this picture, as a consequence of the difference in the velocities of the retrograde precession of the density wave and the orbital rotation of the binary. The variation in the observed number of humps can be explained by the presence of four, rather than two, strong shocks in the flow pattern and the conditions for their visibility at a given observing time.

Vanishing viscosity of isentropic Navier-Stokes equations for interacting shocks

We study the vanishing viscosity of the Navier-Stokes equations for interacting shocks. Given an entropy solution to p -system which consists of two different families of shocks interacting at some positive time, we show that such entropy solution is the vanishing viscosity limit of a family of global smooth solutions to the isentropic Navier-Stokes equations. The key point of the proofs is to derive the estimates separately before and after the interaction time and connect the incoming and outgoing viscous shock profiles.

First X-ray evidence for a shock at the Coma relic

The Coma cluster is one of the nearest galaxy clusters, and the first one in which a peripheral radio relic was discovered. However, X-ray observations of the plasma near the relic have been scarce. Here, we present results from a re-analysis of a 22 ks archival XMM–Newton observation. Across the relic, we detect a temperature discontinuity indicative of a shock of Mach number ∼2. This challenges the previously suggested hypothesis that the relic was formed by turbulence. Furthermore, multiwavelength observations and numerical models do not support the scenario in which the shock is an outgoing cluster-merger shock. Instead, our results lend support to the idea that the relic coincides with an infall shock front formed just as a ‘wall’ of galaxies, possibly associated with NGC 4839, falls on to the cluster along a cosmic filament.