arXiv subjects

Noam Soker

Publications and source records attributed to Noam Soker.

At least 127 records · Page 7Linked to original sources

arXiv2022

Three-dimensional simulations of the jet feedback mechanism in common envelope jets supernova

We conduct three-dimensional hydrodynamical simulations of common envelope jets supernova (CEJSN) events where we assume that a neutron star (NS) launches jets as it orbits inside the outer zones of a red supergiant (RSG) envelope, and find the negative jet feedback coefficient to be ~0.1-0.2. This coefficient is the factor by which the jets reduce the mass accretion rate onto the NS as they remove mass from the envelope and inflate bubbles (cocoons). Our results suggest that in most CEJSN events the NS-RSG binary system experiences the grazing envelope evolution (GEE) before it enters a full common envelope evolution (CEE). We also find that the jets induce upward and downward flows in the RSG envelope. These flows together with the strong convection of RSG stars might imply that energy transport by convection in CEJSNe is very important. Because of limited numerical resources we do not include in the simulations the gravity of the NS, nor the accretion process, nor the jets launching process, and nor the gravity of the deformed envelope. Future numerical simulations of CEE with a NS/BH companion should include the accretion process onto the NS (and vary the jets' power accordingly), the full gravitational interaction of the NS with the RSG, and energy transport by the strong convection.

astro-ph.HE↗

arXiv2022

Remnant masses of core collapse supernovae in the jittering jets explosion mechanism

We conduct one dimensional (1D) stellar evolution simulations of non-rotating stars with initial masses in the range of $11-48 M_\odot$ to the time of core collapse and, using a criterion on the specific angular momentum fluctuations in the inner convective zones, estimate the masses of the neutron star (NS) remnants according to the jittering jets explosion mechanism. From the 1D simulations we find that several convective zones with specific angular momentum fluctuations of $j_{conv} > 2.5 \times 10^{15} cm^2 s^{-1}$ develop near the edge of the iron core in all models. For this condition for explosion we find the NS remnant masses to be in the range of $1.3 -1.8 M_\odot$, while if we require twice as large values, i.e., $j_{conv} > 5 \times 10^{15} cm^2 s^{-1}$, we find the NS remnant masses to be in the range of $1.4 - 2.8 M_\odot$ (the upper values here might form black holes). Note that in general the formation of black holes in the jittering jets explosion mechanism requires a rapidly rotating pre-collapse core, while we simulate non-rotating stars.

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↗

arXiv2022

A common envelope jets supernova (CEJSN) impostor scenario for fast blue optical transients

I propose a new scenario, the polar common envelope jets supernova (CEJSN) impostor scenario, to account for AT2018cow-like fast blue optical transients (FBOTs). The polar CEJSN impostor scenario evolves through four main phases. (1) A red supergiant (RSG) star expands to tidally interact with a neutron star (NS) companion (or a black hole). The interaction increases the RSG mass loss rate to form a circumstellar matter (CSM) halo to ~0.1pc. (2) Shortly before the onset of a common envelope evolution (CEE) and about a year before explosion the NS accretes mass from the RSG envelope and launches jets that inflate two opposite lobes in the CSM within ~100AU. (3) The NS-RSG system enters a CEE phase during which the system ejects most of the envelope mass in a dense equatorial outflow. (4) At the termination of the CEE the leftover envelope forms a circumbinary disk around the NS-core system. The NS accretes mass from the circumbinary disk and launches energetic jets that when collide with the fronts of the CSM lobes power an FBOT event. The low mass of the jets-lobes interaction zones and their large distance, of about 100AU, from the center account for the fast transient. In the future the core collapses to form a second NS. In the far future the two NS might merge. I suggest that FBOTs and similar fast transients are CEJSN impostors which compose a large fraction of the progenitors of NS-NS merger binaries.

astro-ph.HE↗

arXiv2022

A twin-jet structure rather than jet-rotation in the young stellar object OMC 2/FIR 6b

We analyse recent high-quality Atacama Large Millimeter Array (ALMA) molecular line mapping observations of the northeast jet of the young stellar object (YSO) OMC 2/FIR6b (HOPS-60) and find that these ALMA observations are much more likely to indicate a twin-jet structure than jet rotation, as previously hypothesized. The interpretation of the line of sight velocity gradient across (perpendicular to its axis) the northeast jet of Fir6b in terms of jet rotation leads to jet-launching radii of ~2-3AU. However, the velocities of the jets ~100-400 km/s are much larger than the escape speed from these radii. We argue that the northeast jet of FIR6b is instead compatible with a twin-jet structure, as observed in some planetary nebulae. Specifically, we find that the main, redshifted jet emanating from the central YSO is composed of two, very closely aligned, narrower jets that were launched by the central YSO at about the same time but at different inclinations with respect to the plain of the sky. This twin-jet structure removes the extreme requirement that jets with velocities similar to the escape velocity from the YSO be launched from very large radii. The YSO FIR6b and certain planetary nebulae also share the characteristics of unequal structures and intensities of their two opposing bipolar jets. We propose that such opposing lobe asymmetries can result from a sub-stellar binary companion on an eccentric orbit that is inclined to the accretion disk plane.

astro-ph.SR↗

arXiv2022

Common envelope jets supernova r-process yields can reproduce $\rm [Eu/Fe]$ abundance evolution in the Galaxy

We use a numerical Galactic chemical evolution model and find that the common envelope jets supernova (CEJSN) r-process scenario can account for both the very early average ratio of europium to iron and its evolution at later times in the Milky-Way (MW) Galaxy. In the CEJSN scenario a neutron star (NS) spirals-in inside a red supergiant (RSG) star all the way to the core and destroys it. According to this scenario r-process isotopes are nucleosynthesized inside neutron-rich jets that the accretion disk around the NS launches inside the core. The merger of a NS with an RSG core already takes place in the very young Galaxy. We conclude that CEJSNe can be a major contributor to r-process nucleosynthesis.

astro-ph.HE↗

arXiv2022

Astrophysical Naturalness

I suggest that stars introduce mass and density scales that lead to `naturalness' in the Universe. Namely, two ratios of order unity. (1) The combination of the stellar mass scale, M*, with the Planck mass, MPl, and the Chandrasekhar mass leads to a ratio of order unity that reads NPl*=MPl/[(M*)(mp)^2]^{1/3}=0.15-3, where mp is the proton mass. (2) A system with a dynamical time equals to the nuclear life times of stars, tau, has a density of rhoD = 1/[(G)(tau)^2]. The ratio of the dark energy density to this density is NL*=rhoL/rhoD=10^{-7} - 10^{5}$. Although the range is large, it is critically much smaller than the 123 orders of magnitude usually referred to when rhoL is compered to the Planck density. In the pure fundamental particles domain there is no naturalness; either naturalness does not exist or there is a need for a new physics or new particles. The `Astrophysical Naturalness' offers a third possibility: stars introduce the combinations of, or relations among, known fundamental quantities that lead to naturalness.

physics.gen-ph↗

arXiv2022

Common envelope to explosion delay time distribution (CEEDTD) of type Ia supernovae

I use recent observations of circumstellar matter (CSM) around type Ia supernovae (SNe Ia) to estimate the fraction of SNe Ia that explode into a planetary nebula (PN) and to suggest a new delay time distribution from the common envelope evolution (CEE) to the SN Ia explosion for SNe Ia that occur shortly after the CEE. Under the assumption that the CSM results from a CEE, I crudely estimate that about 50 per cent of all SNe Ia are SNe Ia inside PNe (SNIPs), and that the explosions of most SNIPs occur within a CEE to explosion delay (CEED) time of less than about ten thousand years. I also estimate that the explosion rate of SNIPs, i.e., the CEED time distribution (CEEDTD), is roughly constant within this time scale of ten thousand years. The short CEED time suggests than a fraction of SNIPs come from the core-degenerate (CD) scenario where the merger of the core with the white dwarf takes place at the end of the CEE. I present my view that the majority of SNIPs come from the CD scenario. I list some further observations that might support or reject my claims, and the challenge to theoretical studies to find a process to explain a merger to explosion delay (MED) time of up to ten thousand years or so. A long MED will apply also to the double degenerate scenario.

astro-ph.HE↗

arXiv2022

Faint intermediate luminosity optical transients (ILOTs) from engulfing exoplanets on the Hertzsprung gap

We follow the evolution of four observed exoplanets to the time when the respective parent star of each planet evolves off the main sequence and engulfs its planet to start a common envelope evolution (CEE), concluding that in each case this process powers an intermediate luminosity optical transient (ILOT; luminous red nova). We characterise the final thousands of days of the orbital decay towards a CEE and determine the properties of the star at the onset of the CEE. We scale the properties of the ILOT V1309 Scorpii to the properties of a planet that enters a CEE inside a star on and near the Hertzsprung gap to estimate the duration and luminosity of the expected ILOT. Based on these we estimate that for a planet of Jupiter mass the ILOT will last for several days and reach a luminosity of several thousand solar luminosity. This type of ILOTs are less luminous than classical novae. Because of the small amount of expected dust and the small amount of energy that an accretion process onto the planet can release, such ILOTs can teach us on the merger at the onset of CEE of stellar companions. Our study adds to the variety of ILOTs that planets can power as they interact with a more massive companion.

astro-ph.EP↗

arXiv2022

Imprints of the jittering jets explosion mechanism in the morphology of the supernova remnant SNR 0540-69.3

I identify a point-symmetric structure in recently published VLT/MUSE velocity maps of different elements in a plane along the line of sight at the center of the supernova remnant SNR 0540-69.3, and argue that jittering jets that exploded this core collapse supernova shaped this point-symmetric structure. The four pairs of two opposite clumps that compose this point symmetric structure suggest that two to four pairs of jittering jets shaped the inner ejecta in this plane. In addition, intensity images of several spectral lines reveal a faint strip (the main jet-axis) that is part of this plane of jittering jets and its similarity to morphological features in a few other SNRs and in some planetary nebulae further suggests shaping by jets. My interpretation implies that in addition to instabilities, jets also mix elements in the ejecta of core collapse supernovae. Based on the point-symmetric structure and under the assumption that jittering jets exploded this supernova, I estimate the component of the neutron star natal kick velocity on the plane of the sky to be ~235 km/s, and at an angle of 47 degrees to the direction of the main jet-axis. I analyse this natal kick direction together with other 12 SNRs in the frame of the jittering jets explosion mechanism.

astro-ph.HE↗

arXiv2021

Accretion induced merger leading to core collapse supernovae in old stellar populations

We examine a triple-star evolution that might lead to core collapse supernovae (CCSNe) in stellar populations that are too old to allow for single or binary evolution to form CCSNe, i.e., where the most massive stars that evolve off the main sequence have masses of ~4-5Mo. In the scenario we examine the most massive star in the triple system, of mass ~4-5Mo, transfers mass to an inner binary system at an orbital separation of ~100-1000Ro. The initial orbital separation of the inner binary is ~10-50Ro. The inner binary accretes most of the mass that the primary star loses and the two stars expand and their mutual orbit contracts until merger. The merger product is a main sequence star of mass ~8-10Mo that later experiences a CCSN explosion and leaves a NS remnant, bound or unbound to the white dwarf (WD) remnant of the primary star. We estimate the event rate of this WD-NS reverse evolution scenario to be a fraction of ~5e-5 of all CCSNe. We expect that in the coming decade sky surveys will detect 1-5 such events.

astro-ph.HE↗

arXiv2021

Spin-orbit misalignment from triple-star common envelope evolution

I study a triple star common envelope evolution (CEE) of a tight binary system that is spiraling-in inside a giant envelope and launches jets that spin-up the envelope with an angular momentum component perpendicular to the orbital angular momentum of the triple star system. This occurs when the orbital plane of the tight binary system and that of the triple star system are inclined to each other, so the jets are not along the triple star orbital angular momentum. The merger of the tight binary stars also tilts the envelope spin direction. If the giant is a red supergiant (RSG) star that later collapses to form a black hole (BH) the BH final spin is misaligned with the orbital angular momentum. Therefore, CEE of neutron star (NS) or BH tight binaries with each other or with one main sequence star (MSS) inside the envelope of an RSG, where the jets power a common envelope jets supernova (CEJSN) event, might end with a NS/BH-NS/BH close binary system with spin-orbit misalignment. Such binaries can later merge to be gravitational waves sources. I list five triple star scenarios that might lead to spin-orbit misalignments of NS/BH-NS/BH binary systems, two of which predict that the two spins be parallel to each other. In the case of a tight binary system of two MSSs inside an asymptotic giant branch star the outcome is an additional non-spherical component to the mass loss with the formation of a messy planetary nebula.

astro-ph.HE↗

arXiv2021

Comment on "A snapshot of the oldest AGN feedback phases"

We dispute a very recent claim, which is based on new LOFAR radio observations, that mixing does not heat the intragroup medium of the galaxy group Nest200047. We argue to the contrary, namely, that the main heating process is mixing, by showing that the radio morphology of filaments in this galaxy group was qualitatively reproduced by a past three-dimensional hydrodynamical simulation that also showed that the main heating process is by mixing of hot gas from the jet-inflated bubbles with the intracluster (or intragroup) medium.

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↗

arXiv2021

Simulating highly-eccentric common envelope jets supernova (CEJSN) impostors

We conduct three-dimensional hydrodynamical simulations of eccentric common envelope jets supernova (CEJSN) impostors, i.e., a neutron star (NS) that crosses through the envelope of a red supergiant star on a highly eccentric orbit and launches jets as it accretes mass from the envelope. Because of numerical limitations we apply a simple prescription where we inject the assumed jets' power into two opposite conical regions inside the envelope. We find the outflow morphology to be very complicated, clumpy, and non-spherical, having a large-scale symmetry only about the equatorial plane. The outflow morphology can substantially differ between simulations that differ by their jets' power. We estimate by simple means the light curve to be very bumpy, to have a rise time of one to a few months, and to slowly decay in about a year to several years. These eccentric CEJSN impostors will be classified as `gap' objects, i.e., having a luminosity between those of classical novae and typical supernovae (termed also ILOTs for intermediate luminosity optical transients). We strengthen a previous conclusion that CEJSN impostors might account for some peculiar ILOTs, in particular those that might repeat over timescales of months to years.

astro-ph.HE↗

arXiv2021

Supplying angular momentum to the jittering jets explosion mechanism using inner convection layers

We conduct one-dimensional stellar evolution simulations in the mass range $13-20 M_{\odot}$ to late core collapse times and find that an inner vigorous convective zone with large specific angular momentum fluctuations appears at the edge of the iron core during the collapse. The compression of this zone during the collapse increases the luminosity there and the convective velocities, such that the specific angular momentum fluctuations are of the order of j_{conv}~5x10^15cm^2/sec. If we consider that three-dimensional simulations show convective velocities that are three to four times larger than what the mixing length theory gives, and that the spiral standing accretion shock instability in the post-shock region of the stalled shock at a radius of ~100km amplify perturbations, we conclude that the fluctuations that develop during core collapse are likely to lead to stochastic (intermittent) accretion disks around the newly born neutron star. In reaching this conclusion we also make two basic assumptions with uncertainties that we discuss. Such intermittent disks can launch jets that explode the star in the frame of the jittering jets explosion mechanism.

astro-ph.HE↗

arXiv2021

Simulating the negative jet feedback mechanism in common envelope jets supernovae

We use the stellar evolution code MESA to study the negative jet feedback mechanism in common envelope jets supernovae (CEJSNe) where a neutron star (NS) launches jets in the envelope of a red supergiant (RSG), and find that the feedback reduces the mass accretion rate to be $χ_{\rm j} \simeq 0.04-0.3$ times the mass accretion rate without the operation of jets. We mimic the effect of the jets on the RSG envelope by depositing the energy that the jets carry into the envelope zones outside the NS orbit. The energy deposition inflates the envelope, therefore reducing the density in the NS vicinity, which in turn reduces the mass accretion rate in a negative feedback cycle. In calculating the above values for the negative jet feedback coefficient (the further reduction in the accretion rate) $χ_{\rm j}$, we adopt the canonical ratio of jets power to actual accretion power of $0.1$, and the results of numerical simulations that show the actual mass accretion rate to be a fraction of $0.1-0.5$ of the Bondi-Hoyle-Lyttleton mass accretion rate.

astro-ph.HE↗

arXiv2021

Common envelope jets supernovae with a black hole companion as possible high energy neutrino sources

We study high energy neutrino emission from relativistic jets launched by a black hole (BH) spiraling-in inside the envelope of a red supergiant (RSG), and find that such common envelope jets supernovae (CEJSNe) are a potential source for the ~10^15 eV neutrinos detected by IceCube. We first use the stellar evolution code MESA to mimic the effect of the jets on the RSG envelope, and find that the jets substantially inflate the envelope. We then study the propagation of jets inside the extended RSG envelope and find that in most cases the jets do not penetrate the envelope but are rather stalled. We show that such jets can accelerate cosmic rays to high enough energies to produce high energy neutrinos. While the neutrinos stream out freely, the gamma-rays that accompany the neutrino production remain trapped inside the optically thick envelope. This explains the lack of observational association between high energy neutrinos and gamma-rays. We crudely estimate the diffuse neutrino spectrum from a CEJSN and find that CEJSNe with BH companions might have a substantial contribution to the high energy neutrinos flux detected by IceCube.

astro-ph.HE↗