Observations of a Pre-Merger Shock in Colliding Clusters of Galaxies
Liyi Gu, Hiroki Akamatsu, Timothy W. Shimwell, Huib T. Intema, Reinout J. van Weeren, Francesco de Gasperin, Francois Mernier, Junjie Mao, Igone Urdampilleta, J… 展开作者
Liyi Gu, Hiroki Akamatsu, Timothy W. Shimwell, Huib T. Intema, Reinout J. van Weeren, Francesco de Gasperin, Francois Mernier, Junjie Mao, Igone Urdampilleta, Jelle de Plaa, Viral Parekh, Huub J. A. Rottgering, Jelle S. Kaastra
Clusters of galaxies are the largest known gravitationally-bound structures in the Universe. When clusters collide, they create merger shocks on cosmological scales, which transform most of the kinetic energy carried by the cluster gaseous halos into heat. Observations of merger shocks provide key information of the merger dynamics, and enable insights into the formation and thermal history of the large-scale structures. Nearly all of the merger shocks are found in systems where the clusters have already collided, knowledge of shocks in the pre-merger phase is a crucial missing ingredient. Here we report on the discovery of a unique shock in a cluster pair 1E 2216 and 1E 2215. The two clusters are observed at an early phase of major merger. Contrary to all the known merger shocks observed ubiquitously on merger axes, the new shock propagates outward along the equatorial plane of the merger. This discovery uncovers an important epoch in the formation of massive clusters, when the rapid approach of the cluster pair leads to strong compression of gas along the merger axis. Current theoretical models predict that the bulk of the shock energy might be dissipated outside the clusters, and eventually turn into heat of the pristine gas in the circum-cluster space.
We model the diffusive shock acceleration of particles in a system of two colliding shock waves and present a method to solve the time-dependent problem analytically in the test-particle approximation and high energy limit. In particular, we show that in this limit the problem can be analysed with the help of a self-similar solution. While a number of recent works predict hard ($E^{-1}$) spectra for the accelerated particles in the stationary limit, or the appearance of spectral breaks, we found instead that the spectrum of accelerated particles in a time-dependent collision follows quite clos…
Powerful stellar winds and supernova explosions with intense energy release in the form of strong shock waves can convert a sizeable part of the kinetic energy release into energetic particles. The starforming regions are argued as a favorable site of energetic particle acceleration and could be efficient sources of nonthermal emission. We present here a non-linear time-dependent model of particle acceleration in the vicinity of two closely approaching fast magnetohydrodynamic (MHD) shocks. Such MHD flows are expected to occur in rich young stellar cluster where a supernova is exploding in the…
Supersonic interacting flows occurring in phenomena such as protostellar jets give rise to strong shocks, and have been demonstrated in several laboratory experiments. To study such colliding flows, we use the AstroBEAR AMR code to conduct hydrodynamic simulations in three dimensions. We introduce variations in the flow parameters of density, velocity, and cross sectional radius of the colliding flows %radius in order to study the propagation and conical shape of the bow shock formed by collisions between two, not necessarily symmetric, hypersonic flows. We find that the motion of the interact…
We present a model for the non-thermal emission from a colliding-wind binary. Relativistic protons and electrons are assumed to be accelerated through diffusive shock acceleration (DSA) at the global shocks bounding the wind-wind collision region. The non-linear effects of the back-reaction due to the cosmic ray pressure on the particle acceleration process and the cooling of the non-thermal particles as they flow downstream from the shocks are included. We explore how the non-thermal particle distribution and the keV-GeV emission changes with the stellar separation and the viewing angle of th…
A shock wave propagating perpendicularly to an ambient magnetic field accelerates particles considerably faster than in the parallel propagation regime. However, the perpendicular acceleration stops after the shock overruns a circular particle orbit. At the same time, it may continue in flows resulting from supersonically colliding plasmas bound by a pair of perpendicular shocks. Although the double-shock acceleration mechanism, which we consider in detail, is not advantageous for thermal particles, pre-energized particles may avoid the premature end of acceleration. We argue that if their gyr…
We investigate the structure and X-ray emission from the colliding stellar winds in massive star binaries. We find that the opening angle of the contact discontinuity (CD) is overestimated by several formulae in the literature at very small values of the wind momentum ratio. We find also that the shocks in the primary (dominant) and secondary winds flare by approx 20 degrees compared to the CD, and that the entire secondary wind is shocked when the wind momentum ratio < 0.02. Analytical expressions for the opening angles of the shocks, and the fraction of each wind that is shocked, are provide…
The interaction between the strong winds of the stars in colliding-wind binary (CWB) systems produces two shock fronts, delimiting the wind collision region (WCR). There, particles are expected to be accelerated mainly via diffusive shock acceleration, and to produce $γ$-rays, in processes involving relativistic electrons and/or protons. We investigate the injection and the acceleration of protons in typical CWB systems by means of Monte Carlo simulations, with a test-particle approach. We use magnetohydrodynamic simulations to determine the background conditions in the wind collision region. …
In addition to gamma-ray binaries which contain a compact object, high-energy and very high-energy gamma rays have also been detected from colliding-wind binaries. The collision of the winds produces two strong shock fronts, one for each wind, both surrounding a shock region of compressed and heated plasma, where particles are accelerated to very high energies. Magnetic field is also amplified in the shocked region on which the acceleration of particles greatly depends. In this work, we performed full three-dimensional magnetohydrodynamic simulations of colliding winds coupled to a code that e…
We present a model for the creation of non-thermal particles via diffusive shock acceleration in a colliding-wind binary. Our model accounts for the oblique nature of the global shocks bounding the wind-wind collision region and the finite velocity of the scattering centres to the gas. It also includes magnetic field amplification by the cosmic ray induced streaming instability and the dynamical back reaction of the amplified field. We assume that the injection of the ions and electrons is independent of the shock obliquity and that the scattering centres move relative to the fluid at the Alfv…
Cosmic-ray acceleration has been a long-standing mystery and despite more than a century of study, we still do not have a complete census of acceleration mechanisms. The collision of strong stellar winds in massive binary systems creates powerful shocks, which have been expected to produce high-energy cosmic-rays through Fermi acceleration at the shock interface. The accelerated particles should collide with stellar photons or ambient material, producing non-thermal emission observable in X-rays and gamma-rays. The supermassive binary star eta Carinae drives the strongest colliding wind shock …
Eta Carinae shows broad peaks in near-infrared (IR) JHKL photometry, roughly correlated with times of periastron passage in the eccentric binary system. After correcting for secular changes attributed to reduced extinction from the thinning Homunculus Nebula, these peaks have IR spectral energy distributions (SEDs) consistent with emission from hot dust at 1400-1700 K. The excess SEDs are clearly inconsistent, however, with the excess being entirely due to free-free wind or photospheric emission. One must conclude, therefore, that the broad near-IR peaks associated with Eta Carinae's 5.5 yr va…
High velocity clouds moving toward the disk will reach the Galactic plane and will inevitably collide with the disk. In these collisions a system of two shocks is produced, one propagating through the disk and the other develops within the cloud. The shocks produced within the clouds in these interactions have velocities of hundreds of kilometers per second. When these shocks are radiative they may be inefficient in accelerating fresh particles, however they can reaccelerate and compress Galactic cosmic rays from the background. In this work we investigate the interactions of Galactic cosmic r…
We present a new 2 Ms Chandra observation of the cluster merger Abell 2146, which hosts two huge M~2 shock fronts each ~500 kpc across. For the first time, we resolve and measure the width of cluster merger shocks. The best-fit width for the bow shock is 17+/-1 kpc and for the upstream shock is 10.7+/-0.3 kpc. A narrow collisionless shock will appear broader in projection if its smooth shape is warped by local gas motions. We show that both shock widths are consistent with collisionless shocks blurred by local gas motions of 290+/-30 km/s. The upstream shock forms later on in the merger than t…
Two Mpc-size contact discontinuities have recently been identified in the XMM-Newton and Suzaku X-ray observations of the outskirts of the Perseus cluster (Walker et al. 2020). These structures have been tentatively interpreted as "sloshing cold fronts", which are customarily associated with differential motions of the cluster gas, perturbed by a merger. In this study we consider an alternative scenario, namely, that the most prominent discontinuity near the cluster virial radius is the result of the collision between the accretion shock and the "runaway" merger shock. We also discuss the poss…
We present new XMM-Newton observations of the northwest (NW) radio relic region in the cluster Abell 3667. We detect a jump in the X-ray surface brightness and X-ray temperature at the sharp outer edge of the radio relic which indicate that this is the location of a merger shock with a Mach number of about 2. Comparing the radio emission to the shock properties implies that approximately 0.2% of the dissipated shock kinetic energy goes into accelerating relativistic electrons. This is an order of magnitude smaller than the efficiency of shock acceleration in many Galactic supernova remnants, w…
Probing Merger Shocks in Galaxy Clusters in the SKA Era
National Centre for Radio Astrophysics, Tata Institute of Fundamental Research（国家射电天文中心，塔塔基础研究所）；Centre for Radio Astronomy Techniques and Technologies, Rhodes University（射电天文技术与方法中心，罗德斯大学）；Institute of Astronomy, National Tsing Hua University（天文研究所，国立清华大学）；Pole Scientific, University Catholic of Lyon（科学系，里昂天主教大学）；Department of Astronomy, Astrophysics and Space Engineering, Indian Institute of Technology Indore（天文学、天体物理学与空间工程系，印度印度理工学院印多尔分校）
We report the first unambiguous detection of an axial merger shock in the early-stage merging cluster Abell 98 using deep (227 ks) Chandra observations. The shock is about 420 kpc south from the northern subcluster of Abell 98, in between the northern and central subclusters, with a Mach number of M $\approx$ 2.3 $\pm$ 0.3. Our discovery of the axial merger shock front unveils a critical epoch in the formation of a massive galaxy cluster, when two subclusters are caught in the early phase of the merging process. We find that the electron temperature in the post-shock region favors the instant …
Collisional self-interactions occurring in protostellar jets give rise to strong shocks, the structure of which can be affected by radiative cooling within the flow. To study such colliding flows, we use the AstroBEAR AMR code to conduct hydrodynamic simulations in both one and three dimensions with a power law cooling function. The characteristic length and time scales for cooling are temperature dependent and thus may vary as shocked gas cools. When the cooling length decreases sufficiently rapidly the system becomes unstable to the radiative shock instability, which produces oscillations in…
The interaction between the strong winds in stellar colliding-wind binary (CWB) systems produces two shock fronts, delimiting the wind collision region (WCR). There, particles are expected to be accelerated mainly via diffusive shock acceleration (DSA). We investigate the injection and the acceleration of protons in typical CWB systems by means of Monte Carlo simulations, with both a test-particle approach and a non-linear method modelling a shock locally modified by the backreaction of the accelerated protons. We use magnetohydrodynamic simulations to determine the background plasma in the WC…
Neutron star mergers are believed to occur in accretion disks around supermassive black holes. Here we show that a putative jet launched from the merger of a binary neutron star (BNS) or a neutron star--black hole (NSBH) merger occurring at the migration trap in an active galactic nucleus (AGN) disk would be choked. The jet energy is deposited within the disk materials to power a hot cocoon. The cocoon is energetic enough to break out from the AGN disk and produce a bright X-ray shock breakout transient peaking at $\sim0.15\,{\rm d}$ after the merger. The peak luminosity is estimated as $\sim …
A supra-massive neutron star (NS) spinning extremely rapidly could survive from a merger of NS-NS binary. The spin-down of this remnant NS that is highly magnetized would power the isotropic merger ejecta to produce a bright mergernova emission in ultraviolet/optical bands. Before the mergernova, the early interaction between the NS wind and the ejecta can drive a forward shock propagating outwards into the ejecta. As a result, a remarkable amount of heat can be accumulated behind the shock front and the final escaping of this heat can produce a shock breakout emission. We describe the dynamic…
WR 20a is the most massive close-in binary known in our Galaxy. It is composed of two $\approx$80 M$_\odot$ Wolf-Rayet stars with a short period of $\approx$3.7 days in the open cluster Westerlund 2. As such, WR 20a presents us with a unique laboratory for studying the currently uncertain physics of binary evolution and compact object formation as well as for studying the wind collision region in an massive eclipsing binary system. We use deep Chandra observations of WR 20a to study the time variability of the wind collision region between the two Wolf-Rayet stars and are able to produce an X-…
We present deep Chandra, XMM-Newton, Giant Metrewave Radio Telescope and Halpha observations of the group-group merger NGC 6338. X-ray imaging and spectral mapping show that as well as trailing tails of cool, enriched gas, the two cool cores are embedded in an extensive region of shock heated gas with temperatures rising to ~5 keV. The velocity distribution of the member galaxies show that the merger is occurring primarily along the line of sight, and we estimate that the collision has produced shocks of Mach number M=2.3 or greater, making this one of the most violent mergers yet observed bet…
Moderately strong shocks arise naturally when two subclusters merge. For instance, when a smaller subcluster falls into the gravitational potential of a more massive cluster, a bow shock is formed and moves together with the subcluster. After pericenter passage, however, the subcluster is decelerated by the gravity of the main cluster, while the shock continues moving away from the cluster center. These shocks are considered as promising candidates for powering radio relics found in many clusters. The aim of this paper is to explore the fate of such shocks when they travel to the cluster outsk…
A rapidly rotating and highly magnetized remnant neutron star (NS; magnetar) could survive from a merger of double NSs and drive a powerful relativistic wind. The early interaction of this wind with the previous merger ejecta can lead to shock breakout (SBO) emission mainly in ultraviolet and soft X-ray bands, which provides an observational signature for the existence of the remnant magnetar. Here we investigate the effect of an anisotropic structure of the merger ejecta on the SBO emission. It is found that bolometric light curve of the SBO emission can be broadened, since the SBO can occur …
Several colliding-wind massive binaries are known to be non-thermal emitters in the radio domain. This constitutes strong evidence for the fact that an efficient particle acceleration process is at work in these objects. The acceleration mechanism is most probably the Diffusive Shock Acceleration (DSA) process in the presence of strong hydrodynamic shocks due to the colliding-winds. In order to investigate the physics of this particle acceleration, we initiated a multiwavelength campaign covering a large part of the electromagnetic spectrum. In this context, the detailed study of the hard X-ra…
When a subcluster merges with a larger galaxy cluster, a bow shock is driven ahead of the subcluster. At a later merger stage, this bow shock separates from the subcluster, becoming a "runaway" shock that propagates down the steep density gradient through the cluster outskirts and approximately maintains its strength and the Mach number. Such shocks are plausible candidates for producing radio relics in the periphery of clusters. We argue that, during the same merger stage, a secondary shock is formed much closer to the main cluster center. A close analog of this structure is known in the usua…
Abell1758 is a system of two galaxy clusters, a more massive, northern cluster and a southern cluster. Both parts are undergoing major merger events at different stages. Although the mass of the merger constituents provides enough energy to produce visible shock fronts in the X-ray, none have been found to date. We present detailed temperature and abundance maps based on Chandra ACIS data, and identify several candidates for shocks and cold fronts from a smoothed gradient map of the surface brightness. One candidate can be confirmed as the missing shock front in the northern cluster through X-…
The afterglows to gamma-ray bursts (GRBs) are due to synchrotron emission from shocks generated as an ultra-relativistic outflow decelerates. A forward and a reverse shock will form, however, where emission from the forward shock is well studied as a potential counterpart to gravitational wave-detected neutron star mergers the reverse shock has been neglected. Here, we show how the reverse shock contributes to the afterglow from an off-axis and structured outflow. The off-axis reverse shock will appear as a brightening feature in the rising afterglow at radio frequencies. For bursts at $\sim10…
The supernova remnant (SNR) HESS J1731-347 is a young SNR which displays a non-thermal X-ray and TeV shell structure. A molecular cloud at a distance of 3.2 kpc is spatially coincident with the western part of the SNR, and it is likely hit by the SNR. The X-ray emission from this part of the shell is much lower than from the rest of the SNR. Moreover, a compact GeV emission region coincident with the cloud has been detected with a soft spectrum. These observations seem to imply a shock-cloud collision scenario at this area, where the stalled shock can no longer accelerate super-TeV electrons o…
Deep (103 ks) \chandra\ observations of Abell 665 have revealed rich structures in this merging galaxy cluster, including a strong shock and two cold fronts. The newly discovered shock has a Mach number of $M$ = 3.0 $\pm$ 0.6, propagating in front of a cold disrupted cloud. This makes Abell~665 the second cluster where a strong merger shock of $M \approx$ 3 has been detected, after the Bullet cluster. The shock velocity from jump conditions is consistent with (2.7 $\pm$ 0.7) $\times$ 10$^3$ km sec$^{-1}$. The new data also reveal a prominent southern cold front, with potentially heated gas ahe…
The first electromagnetic signal observed in different types of cosmic explosions is released upon emergence of a shock created in the explosion from the opaque envelope enshrouding the central source. Notable examples are the early emission from various types of supernovae and low luminosity GRBs, the prompt photospheric emission in long GRBs, and the gamma-ray emission that accompanied the gravitational wave signal in neutron star mergers. In all of these examples, the shock driven by the explosion is mediated by the radiation trapped inside it, and its velocity and structure, that depend on…
Fast ejecta expelled in binary neutron star (NS) mergers or energetic supernovae (SNe) should produce late-time synchrotron radio emission as the ejecta shocks into the surrounding ambient medium. Models for such radio flares typically assume the ejecta expands into an unperturbed interstellar medium (ISM). However, it is also well-known that binary NS mergers and broad-lined Ic SNe can harbor relativistic jetted outflows. In this work, we show that such jets shock the ambient ISM ahead of the ejecta, thus evacuating the medium into which the ejecta subsequently collides. Using an idealized sp…
We present high resolution simulations with RAMSES of supersonic colliding stellar winds. The collision results in a double shock structure which is subject to different instabilities. The Kelvin-Helmholtz instability (KHI) introduces some mixing and variability. For isothermal winds, the Non-linear Thin Shell Instability violently affects the interaction region. Properly modelling these instabilities requires a high enough resolution and an adapted numerical method, especially when one of the winds strongly dominates the other one. At large scale, orbital motion is expected to turn the shocke…
The study of short-duration gamma-ray bursts provides growing evidence that a good fraction of double neutron star mergers lead to the formation of stable millisecond magnetars. The launch of Poynting flux by the millisecond magnetars could leave distinct electromagnetic signatures that reveal the energy dissipation processes in the magnetar wind. In previous studies (Wang & Dai 2013b; Wang et al. 2015), we assume that the magnetar wind becomes completely lepton-dominated so that electrons/positrons in the magnetar wind are accelerated by a diffusive shock. However, theoretical modeling of pul…
The shocking features in the closest rich galaxy cluster Norma
Xiamen University（厦门大学）；University of Alabama in Huntsville（阿拉巴马大学亨茨维尔分校）；Rhodes University（罗德岛大学）；INAF-Osservatorio Astronomico di Cagliari（意大利国家天体物理研究所卡利亚里天文台）；Gustavus Adolphus College（古斯塔夫斯阿道夫学院）；Australia Telescope National Facility, CSIRO（澳大利亚望远镜国家设施，CSIRO）；Western Sydney University（西悉尼大学）
The importance of shocks in nova explosions has been highlighted by Fermi's discovery of γ-ray producing novae. Over three years of multi-band VLA radio observations of the 2010 nova V1723 Aql show that shocks between fast and slow flows within the ejecta led to the acceleration of particles and the production of synchrotron radiation. Soon after the start of the eruption, shocks in the ejecta produced an unexpected radio flare, resulting in a multi-peaked radio light curve. The emission eventually became consistent with an expanding thermal remnant with mass $2 \times 10^{-4} M_\odot$ and tem…
Radio relics in galaxy clusters are extended synchrotron sources produced by cosmic-ray electrons in the $μ$G magnetic field. Many relics are found in the cluster periphery and have a cluster-centric, narrow arc-like shape, which suggests that the electrons are accelerated or re-accelerated by merger shock fronts propagating outward in the intracluster plasma. In the X-ray, some relics do exhibit such shocks at the location of the relic, but many do not. We explore the possibility that radio relics trace not the shock fronts but the shape of the underlying distribution of seed relativistic ele…
We investigate the shock acceleration of particles in massive galaxy mergers or collisions, and show that cosmic rays (CRs) can be accelerated up to the second knee energy ~0.1-1 EeV and possibly beyond, with a hard spectral index Gamma ~ 2. Such CRs lose their energy via hadronuclear interactions within a dynamical timescale of the merger shock, producing gamma rays and neutrinos as a by-product. If ~ 10 % of the shock dissipated energy goes into CR acceleration, some local merging galaxies will produce gamma-ray counterparts detectable by CTA. Also, based on the concordance cosmology, where …
Numerical simulations of shock-driven, supersonic interstellar turbulence in colliding three-temperature laboratory plasmas
Imperial College London（帝国理工学院）；Princeton University（普林斯顿大学）；University of Toronto（多伦多大学）；Lawrence Livermore National Laboratory（劳伦斯利弗莫尔国家实验室）；Massachusetts Institute of Technology（麻省理工学院）
Massive stars in binary systems (as WR140, WR147 or $η$ Carinae) have long been regarded as potential sources of high-energy $γ$-rays. The emission is thought to arise in the region where the stellar winds collide and produce relativistic particles which subsequently might be able to emit $γ$-rays. Detailed numerical hydrodynamic simulations have already offered insight in the complex dynamics of the wind collision region (WCR), while independent analytical studies, albeit with simplified descriptions of the WCR, have shed light on the spectra of charged particles. In this paper, we describe a…
The $η$ Carinae binary system is the first $γ$-ray binary ever observed which does not contain a compact object. The dense wind of the primary star shocks against the fast light wind coming from the companion star, creating the conditions to accelerate particles up to relativistic energies via Fermi mechanisms. These relativistic particles subsequently dissipates non-thermal radiation. Fermi-LAT and H.E.S.S. detection of $η$ Carinae confirm such hypotheses. Hydrodynamic simulations provide a convincing match to the observations if a few percent of the wind mechanical energy dissipated in the s…
(abridged)The structure formed by the shocked winds of a massive star and a non-accreting pulsar in a binary suffers periodic and random variations of orbital and non-linear dynamical origin. For the 1st time, we simulate in 3 D the interaction of isotropic stellar and relativistic pulsar winds along 1 full orbit, on scales well beyond the binary size. We also investigate the impact of grid resolution and size, and of different EoOs: a gamma-constant ideal gas, and an ideal gas with gamma dependent on temperature. We carry out, with the code PLUTO, relativistic HD simulations in 2 and 3 D of t…
During the final stages of a compact object merger, if at least one of the binary components is a magnetized neutron star (NS), then its orbital motion substantially expands the NS's open magnetic flux -- and hence increases its wind luminosity -- relative to that of an isolated pulsar. As the binary orbit shrinks due to gravitational radiation, the power and speed of this binary-induced inspiral wind may (depending on pair loading) secularly increase, leading to self-interaction and internal shocks in the outflow beyond the binary orbit. The magnetized forward shock can generate coherent radi…
We perform GRMHD and RMHD simulations of weakly and highly magnetized gamma-ray burst (GRB) jets propagating in binary neutron star (BNS) merger ejecta. Using the simulations, we first find that mixing between the jet and cocoon, which is present in all types of jets, inhibits the formation of subphotospheric collisionless shocks. However, we show that a mild magnetization may lead to the formation of collisionless subshocks which allow efficient proton acceleration. We consider shear acceleration and diffusive shock acceleration at collimation shocks, internal shocks, shock breakout, and exte…
Luminous red novae (LRN) are a class of optical transients believed to originate from the mergers of binary stars, or "common envelope" events. Their light curves often show secondary maxima, which cannot be explained in the previous models of thermal energy diffusion or hydrogen recombination without invoking multiple independent shell ejections. We propose that double-peaked light curves are a natural consequence of a collision between dynamically-ejected fast shell and pre-existing equatorially-focused material, which was shed from the binary over many orbits preceding the dynamical event. …
Merging neutron stars generate shock waves that disintegrate heavy nuclei into nucleons especially in the outer envelope. It is expected that some of such neutrons having avoided capturing positrons remain as free neutrons even after disappearance of electron-positron pairs. To investigate how many free neutrons can be ejected from merging neutron stars, we performed special-relativistic Lagrangian hydrodynamics computation with simplified models of this phenomenon in which a spherically symmetric shock wave propagates in the hydrostatic envelope and emerge from the surface. We systematically …
While dark matter self-interactions may solve several problems with structure formation, so far only the effects of two-body scatterings of dark matter particles have been considered. We show that, if a subdominant component of dark matter is charged under an unbroken $U(1)$ gauge group, collective dark plasma effects need to be taken into account to understand its dynamics. Plasma instabilities can lead to collisionless dark matter shocks in galaxy cluster mergers which might have been already observed in the Abell 3827 and 520 clusters. As a concrete model we propose a thermally produced dar…
Neutron star mergers (NSMs) eject energetic sub-relativistic dynamical ejecta into the circumbinary media. As analogous to supernovae and supernova remnants, the NSM dynamical ejecta are expected to produce non-thermal emission by electrons accelerated at a shock wave. In this paper, we present expected radio and X-ray signals by this mechanism, taking into account non-linear diffusive shock acceleration (DSA) and magnetic field amplification. We suggest that the NSM has a unique nature as a DSA site, where the seed relativistic electrons are abundantly provided by the decays of r-process elem…
