arXiv subjects

Muhammad Akashi

Publications and source records attributed to Muhammad Akashi.

At least 19 recordsLinked to original sources

arXiv2026

Simulating observed point-symmetric core-collapse supernova morphologies with the jittering jets explosion mechanism

We conduct two three-dimensional hydrodynamic simulations of the jittering-jets explosion mechanism (JJEM) of core-collapse supernova (CCSN), launching three pairs of inclined opposite jets into the core of an enveloped-stripped stellar model, and reproduce some morphological features of observed CCSN remnants (CCSNRs) that a single pair of jets or instabilities alone cannot reproduce. We launch the three pairs of jets within about a second, and follow the ejecta for more than 10 seconds until after shock breakout. Our main findings are: (1) Although the jets are choked deep inside the star, they manage to form a pronounced multipolar (point-symmetric) morphology. (2) Instabilities and vortices resulting from the jet-star interaction form small clumps and narrow filaments, some of which form point-symmetric morphology, resembling some observed CCSNRs. (3) The most energetic jet of one simulation forms a large low-density blowout ahead of the ejecta, with filaments dragging behind it, resembling the blowout of the Cygnus Loop. (4) The inner ejecta presents two symmetry axes along two of the three jet axes: one of a pair of rings and one of a pair of nozzles, resembling the structure of the point-symmetric SNR J0450.4-7050. (5) The three pairs of jets compress two dense blocks between their axes. The blocks exhibit a Doppler-shift bipolar outflow highly inclined to the morphological axes along the jet axes. The inclined Doppler-bipolar outflow and morphology axis resembles the CCSNRe W49B and SNR G292.0+1.8. Our study supports the claim that the JJEM is the primary explosion mechanism of CCSNe.

astro-ph.HE↗

arXiv2026

Reproducing morphological features in the supernova remnant G11.2-0.3 by simulating jittering jets

We hydrodynamically simulate a core-collapse supernova (CCSN) explosion by launching three pairs of jets in the framework of the jittering-jets explosion mechanism (JJEM), and reproduce a morphology of two opposite circum-jet rings and a bar of dense gas perpendicular to the rings' axis, resembling these morphological features in the CCSN remnant SNR G11.2-0.3. The first pair of wide jets is very energetic; it triggers the explosion and inflates two bubbles that compress the material in an expanding shell. The bubbles also compress material in a plane perpendicular to the jet axis. The second pair of wide jets removes material from this plane, beside along a bar that is on an axis perpendicular to the two pairs' axes. The jets of the third pair, now of narrow jets, penetrate the expanding shell and compress material to their sides to form two opposite rings. These morphological features are qualitatively similar to those observed in the point-symmetric CCSN remnant G11.2-0.3. As competing theoretical CCSN explosion mechanisms cannot explain point-symmetric CCSN remnants, our study provides some support for the claim that the JJEM is the primary explosion mechanism of CCSNe.

astro-ph.HE↗

arXiv2026

Simulating the jittering-jets explosion mechanism: circum-jet rings account for observed core-collapse supernova remnant morphologies

We conduct three-dimensional hydrodynamical simulations of core-collapse supernova (CCSN) explosion driven by jets in the framework of the jittering jets explosion mechanism (JJEM), and obtain a pair of opposite circum-jet rings similar to those observed in some CCSN remnants (CCSNRs). We launch two pairs of jets along the same axis, the first of two opposite wide jets, and the second of narrow jets. The wide jets compress the core of a stripped-envelope stellar model to form a dense, fast-expanding shell. The narrow jets catch up with the dense shell, penetrate it, and compress the gas to the sides, forming the two opposite rings. At high inclination angles of the jets' axis to the line of sight, the projection of each ring on the plane of the sky forms two bright zones, where the rings cross the plane of the sky. This morphology explains that of SNR G46.8-0.3. At intermediate inclination angles, the rings are fully visible as two opposite bright elliptical rims. Our simulations explain the two prominent rings on the outer shell of CCSNR G11.2-0.3. Our results strengthen the claim that the JJEM is the primary explosion mechanism of CCSNe.

astro-ph.HE↗

arXiv2025

The explosion jets of the core-collapse supernova remnant Circinus X-1

We propose that the recently analyzed opposite rings in the Circinus X-1 (Cir X-1) core collapse supernova (CCSN) remnant resulted from a pair of opposite jets at the final phases of the jet-driven explosion process of the progenitor of Cir X-1. We point out the similarity of the rings in the Cir X-1 CCSN remnant to a ring in the Cygnus Loop CCSN remnant. While the X-ray binary system Cir X-1 actively launches jets, no such activity exists in the Cygnus Loop. In both CCSN remnants, we attribute the rings to jets associated with the explosion process, within the framework of the jittering-jets explosion mechanism (JJEM). We also identify such a ring in the CCSN remnant 107.7-5.1, which we also attribute to exploding jets. We conduct three-dimensional hydrodynamical simulations of late jets inside an exploding massive stellar core, and demonstrate the feasibility of this scenario for ring formation. The Cir X-1 CCSN remnant has a large blowout, similar to that of the Cygnus Loop and to a large protrusion in the CCSN remnant G0.9+0.1. Based on these similarities, we suggest that other exploding jets inflated the blowout of the Cir X-1 nebula, consistent with an earlier claim regarding the formation of the blowout of the Cygnus Loop. We identify a point-symmetric structure in the Cir X-1 CCSN remnant, strengthening the JJEM. This study further demonstrates that the JJEM is a successful explosion mechanism to analyze CCSNe and CCSN remnants.

astro-ph.HE↗

arXiv2025

Jet-Driven Formation of Bipolar Rings in Planetary Nebulae: Numerical Simulations Inspired by NGC 1514

We conduct three-dimensional hydrodynamical simulations of jets launched into a dense shell, reproducing two rings in a bipolar structure that resemble the two dusty rings of the planetary nebula (PN) NGC 1514. The scenario we simulate assumes that a strong binary interaction enhanced the mass loss rate from the asymptotic giant branch (AGB) stellar progenitor of NGC 1514, and shortly thereafter, the main-sequence companion accreted mass from the AGB star, launching a pair of jets. We find that adiabatic flows, where radiative losses are negligible, produce prominent rings, as observed in the infrared in NGC 1514. In contrast, when radiative cooling is significant, the rings are thin and faint. Our results reinforce the prevailing notion that jets play a substantial role in shaping planetary nebulae (PNe). More generally, as the binary companion to the central star of NGC 1514 avoided common envelope evolution, our results suggest that jets play a major role in many binary systems experiencing stable mass transfer at high rates. This conclusion complements the view that jets play a significant role in unstable mass transfer, specifically in common envelope evolution. Studies of strongly interacting binary systems, whether stable or not, should include jets. If jets continue to be active after ring formation, the outcomes are circum-jet rings, as observed in some other PNe and core-collapse supernova remnants.

astro-ph.SR↗

arXiv2025

Simulating the shaping of point-symmetric structures in the jittering jets explosion mechanism

We conduct three-dimensional hydrodynamical simulations of core-collapse supernovae by launching several pairs of jets into a collapsing core model and show that the jittering jets explosion mechanism (JJEM) can form a point-symmetric morphology that accounts for observed morphologies of about a dozen core-collapse supernovae (CCSN) remnants. Point-symmetric morphologies are composed of pairs of opposite structures around the center of the CCSN remnant. In the JJEM, the newly born neutron star launches several to a few tens of pairs of jets with stochastically varying directions, and these jets explode the star. In the simulations with the FLASH numerical code, we launch pairs of jets with varying directions, energies, opening angles, and durations into the massive stellar core and follow their evolution for about two seconds. We show that the jets form pairs of opposite filaments, clumps, bubbles, and lobes, namely, prominent point-symmetric morphologies. The interaction of the jets with the core leads to vigorous Rayleigh-Taylor instabilities and excites many vortices, which also shape clumps and filaments. Our results suggest that the JJEM could play a central role in the explosion mechanism of CCSNe; neutrino heating can boost the role of jets.

astro-ph.HE↗

arXiv2023

The messy death of a multiple star system and the resulting planetary nebula as observed by JWST

Planetary nebulae (PNe), the ejected envelopes of red giant stars, provide us with a history of the last, mass-losing phases of 90 percent of stars initially more massive than the Sun. Here, we analyse James Webb Space Telescope (JWST) Early Release Observation (ERO) images of the PN NGC3132. A structured, extended H2 halo surrounding an ionised central bubble is imprinted with spiral structures, likely shaped by a low-mass companion orbiting the central star at 40-60 AU. The images also reveal a mid-IR excess at the central star interpreted as a dusty disk, indicative of an interaction with another, closer companion. Including the previously known, A-type visual companion, the progenitor of the NGC3132 PN must have been at least a stellar quartet. The JWST images allow us to generate a model of the illumination, ionisation and hydrodynamics of the molecular halo, demonstrating the power of JWST to investigate complex stellar outflows. Further, new measurements of the A-type visual companion allow us to derive the value for the mass of the progenitor of a central star to date with excellent precision: 2.86+/-0.06 Mo. These results serve as path finders for future JWST observations of PNe providing unique insight into fundamental astrophysical processes including colliding winds, and binary star interactions, with implications for supernovae and gravitational wave systems.

astro-ph.SR↗

arXiv2022

Rapid decline in the lightcurves of luminous supernovae by jet-driven bipolar explosions

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.

astro-ph.HE↗

arXiv2022

Post-explosion positive jet-feedback activity in inner ejecta of core collapse supernovae

We conduct three-dimensional hydrodynamical simulations of weak jets that we launch into a core collapse supernovae (CCSNe) ejecta half an hour after the explosion and find that the interaction of the fast jets with the CCSN ejecta creates high pressure zones that induce a backflow that results in mass accretion onto the newly born neutron star. In cases of weak jets, a total power of 10^45-10^46 erg, the backflow mass accretion might power up to an order of magnitude more energetic jets. In total, the jets of the two post-explosion jet-launching episodes have enough energy to influence the morphology of the very inner ejecta, a mass of 0.1 M_O. Our results imply that in some, probably a minority of, CCSN remnants the very inner regions might display a bipolar structure that results from post-explosion weak jets. The regions outside this part might display the morphology of jittering jets.

astro-ph.HE↗

arXiv2021

Simulating the outcome of binary neutron star merger in common envelope jets supernovae

We simulate the influence of the energy that the merger process of two neutron stars (NSs) releases inside a red supergiant (RSG) star on the RSG envelope inner to the merger location. In the triple star common envelope evolution (CEE) that we consider a tight binary system of two NSs spirals-in inside an RSG envelope and because of mass accretion and dynamical friction the two NS merge. We deposit merger-explosion energies of 3e50 and 1e51 erg at distances of 25Ro and 50Ro from the center of the RSG, and with the three-dimensional hydrodynamical code FLASH we follow the evolution of the RSG envelope in inner regions. For the parameters we explore we find that more than 90 per cent of the RSG envelope mass inner to the merger site stays bound to the RSG. NSs that experience a CEE are likely to accrete RSG envelope mass through an accretion disk that launches jets. These jets power a luminous transient event, a common envelope jets supernova (CEJSN). The merger process adds to the CEJSN energy. Our finding implies that the interaction of the merger product, a massive NS or a BH, with the envelope can continue to release more energy, both by further in-spiral and by mass accretion by the merger product. Massive RSG envelopes can force the merger product to spiral-in into the core of the RSG, leading to an even more energetic CEJSN.

astro-ph.HE↗

arXiv2020

Shaping `Ears' in planetary nebulae by early jets

We conduct three dimensional hydrodynamical numerical simulations of planetary nebula (PN) shaping and show that jets that precede the ejection of the main PN shell can form the morphological feature of ears. Ears are two opposite protrusions from the main nebula that are smaller than the main nebula and with a cross section that decreases monotonically from the base of an ear at the shell to its far end. Only a very small fraction of PNe has ears. The short-lived jets, about a year in the present simulations, interact with the regular asymptotic giant branch (AGB) wind to form the ears, while the later blown dense wind forms the main PN dense shell. Namely, the jets are older than the main PN shell. We also find that for the jets to inflate ears they cannot be too energetic, cannot be too wide, and cannot be too slow. A flow structure where short-lived jets precede the main phase of nebula ejection by a few years or less can result from a system that enters a common envelope evolution. The low mass companion accretes mass through an accretion disk and launches jets just before it enters the envelope of the giant progenitor star of the PN. Shortly after that the companion enters the envelope and spirals-in to eject the envelope that forms the main PN shell.

astro-ph.GA↗

arXiv2020

Simulating jets from a neutron star companion hours after a core collapse supernova

We conduct three-dimensional hydrodynamical simulations to explore the interaction of jets that a neutron star (NS) companion to a type Ic or type Ib core collapse supernova (CCSN) launches few hours after explosion with the ejecta of the CCSN. We assume that a NS companion at 5Ro from the exploding star accretes mass from the slower inner ejecta through an accretion disk, and that the disk launches two opposite jets. Although the energy of the jets is only about one per cent of the total energy of the ejecta, it is comparable to the energy of the slower inner part of the ejecta. We find that the jets inflate one low-density hot bubble to one side of the ejecta, and that this bubble expands to influence ejecta gas up to expansion velocities of v=3500 km/s. The post-shock jets' material develops a large meridional flow and small vortexes. The boundary between the ejecta and jets' post-shock gases is unstable. The instabilities and vortexes mix jets' gas with the ejecta. We expect such a hot bubble to contribute to the light curve of CCSNe that are progenitors of binary NS systems, in particular to observers on the side of the bubble.

astro-ph.HE↗

arXiv2020

Simulating the inflation of bubbles by late jets in core collapse supernova ejecta

We conducted three-dimensional hydrodynamical simulations to study the interaction of two late opposite jets with the ejecta of a core collapse supernova (CCSN), and study the bipolar structure that results from this interaction as the jets inflate hot-low-density bubbles. The newly born central object, a neutron star (NS; or a black hole), launches these jets at about 50 to 100 days after explosion. The bubbles cross the photosphere in the polar directions at much earlier times than the regions at the same radii near the equatorial plane. The hot bubbles releases more radiation and the photosphere recedes more rapidly in the tenuous bubble. Our results strengthen earlier claims that were based on toy models that such an interaction might lead to a late peak in the light curve, and that an equatorial observer might see a rapid drop in the light curve. Our results might have implications to much earlier jets that explode the star, either jets that the newly born NS launches in a CCSN, or jets that a NS companion that merges with the core of a massive star launches in a common envelope jets supernova (CEJSN) event. Our results add indirect support to the CEJSN scenario for fast blue optical transients, e.g., AT2018cow, ZTF18abvkwla, and CSS161010.

astro-ph.HE↗

arXiv2020

Fast Ejecta Resulted from Jet-Wind Interaction in the Great Eruption of Eta Carinae

The accretion model for the nineteenth century Great Eruption (GE) of $\eta$ Carinae suggests that mass outflowing from the primary was accreted onto the secondary, and the gravitational energy of that mass accounts for the increase in luminosity and most of the kinetic energy of the ejecta. It further argues that the accretion was accompanied by the ejection of two jets that shaped the bipolar Homunculus nebula. Observations of echos from the GE found emission lines with broad wings suggesting some of the mass in equatorial directions reached more than $10\,000 \,\rm{km\,s^{-1}}$. We run hydrodynamic simulations following periastron passage during the GE, launching jets from the secondary as it accreted gas erupted from the primary. We then follow the interaction of the polar jets with the surrounding primary wind, as they accelerate part of the flow to velocities $ > 10\,000 \,\rm{km\,s^{-1}}$ and deflect it towards lower latitudes. We find that the amount of mass that reached these high velocities during the GE is $M_h \approx 0.02 \,\rm{M_{\odot}}$. This value reaches maximum and then decreases with time. Our simulations agree with previous results of the accretion model from which we estimate $M_h$ taking into account the energy budget of the GE. The accretion model can explain the observations of high velocity gas in light echos with the known two stars, and a triple star system is not required.

astro-ph.SR↗

arXiv2018

The formation of `columns crowns' by jets interacting with a circumstellar dense shell

We conduct three-dimensional hydrodynamical simulations of two opposite jets that interact with a spherical slow wind that includes a denser shell embedded within it, and obtain a bipolar nebula where each of the two lobes is composed of two connected bubbles and Rayleigh-Taylor instability tongues that protrude from the outer bubble and form the `columns crown'. The jets are launched for a short time of 17 years and inflate a bipolar nebula inside a slow wind. When the bipolar structure encounters the dense shell, the interaction causes each of the two lobes to split to two connected bubbles. The interaction is prone to Rayleigh-Taylor instabilities that form tongues that protrude as columns from the outer bubble. The bases of the columns form a ring on the surface of the outer bubble, and the structure resemble a crown that we term the columns crown. This structure resembles, but is not identical to, the many filaments that protrude from the lobes of the bipolar planetary nebula Menzel~3. We discuss our results in comparison to the structure of Menzel~3 and the ways by which the discrepancies can be reconciled, and possibly turn our failure to reproduce the exact structure of Menzel~3 to a success with jets-shell interaction simulations that include more ingredients.

astro-ph.SR↗

arXiv2017

Forming H-shaped and barrel-shaped nebulae with interacting jets

We conduct three-dimensional hydrodynamical simulations of two opposite jets launched from a binary stellar system into a previously ejected shell and show that the interaction can form barrel-like and H-like shapes in the descendant nebula. Such features are observed in planetary nebulae and supernova remnants. Under our assumption the dense shell is formed by a short instability phase of the giant star as it interacts with a stellar companion, and the jets are then launched by the companion as it accretes mass through an accretion disk from the giant star. We find that the H-shaped and barrel-shaped morphological features that the jets form evolve with time, and that there are complicated flow patterns, such as vortices, instabilities, and caps moving ahead along the symmetry axis. We compare our numerical results with images of 12 planetary nebulae, and show that jet-shell interaction that we simulate can account for the barrel-like or H-like morphologies that are observed in these PNe.

astro-ph.SR↗

arXiv2017

Shaping planetary nebulae with jets in inclined triple stellar systems

We conduct three-dimensional hydrodynamical simulations of two opposite jets launched obliquely to the orbital plane around an asymptotic giant branch (AGB) star and within its dense wind, and demonstrate the formation of a `messy' planetary nebula (PN), namely, a PN lacking any type of symmetry (highly irregular). In building the initial conditions we assume that a tight binary system orbits the AGB star, and that the orbital plane of the tight binary system is inclined to the orbital plane of the binary system and the AGB star (the triple system plane). We further assume that the accreted mass on to the tight binary system forms an accretion disk around one of the stars, and that the plane of the disk is tilted to the orbital plane of the triple system. The highly asymmetrical and filamentary structure that we obtain support the notion that messy PNe might be shaped by triple stellar systems.

astro-ph.SR↗

arXiv2016

Bipolar rings from jet-inflated bubbles around evolved binary stars

We show that a fast wind that expands into a bipolar nebula composed of two opposite jet-inflated bubbles can form a pair of bipolar rings around giant stars. Our model assumes three mass loss episodes: a spherical slow and dense shell, two opposite jets, and a spherical fast wind. We use the FLASH hydrodynamical code in three-dimensions to simulate the flow, and obtain the structure of the nebula. We assume that the jets are launched from an accretion disk around a stellar companion to the giant star. The accretion disk is assumed to be formed when the primary giant star and the secondary star suffer a strong interaction accompanied by a rapid mass transfer process from the primary to the secondary star, mainly a main sequence star. Later in the evolution the primary star is assumed to shrink and blow a fast tenuous wind that interacts with the dense gas on the surface of the bipolar structure. We assume that the dense mass loss episode before the jets are launched is spherically symmetric. Our results might be applicable to some planetary nebulae, and further emphasize the large variety of morphological features that can be formed by jets. But we could not reproduce some of the properties of the outer rings of SN1987A. It seems that some objects, like SN1987A, require a pre-jets mass loss episode with a mass concentration at mid-latitudes.

astro-ph.SR↗