arXiv subjects

Ealeal Bear

Publications and source records attributed to Ealeal Bear.

At least 19 recordsLinked to original sources

arXiv2026

High mass accretion rates onto evolved stripped-envelope massive stars by jet-induced mass removal

Simulating one-dimensional stellar evolution models with MESA, we show that removing the outer inflated envelope of a mass-accreting evolved stripped-envelope star, like a Wolf-Rayet (WR) star, substantially moderates the stellar expansion during accretion at high-mass accretion rates. We study the accretion onto a star via an accretion disk, which launches jets that remove the high-entropy outer layers of the inflated envelope. This is the `jetted mass removal accretion scenario.' By manually removing the entire hydrogen-rich envelope from a red supergiant, we build a hydrogen-deficient WR stellar model with a mass of 6.03Mo and a radius of 0.67Ro. We then accrete mass onto it at a high rate. We mimic the real process of simultaneous mass addition near the equatorial plane and jet-induced mass removal from the outer envelope by dividing the accretion period into hundreds of pulses: in the first half of each pulse, we add mass, and in the second, we remove a fraction of this mass. The removal of tens of percent from the added mass decreases the stellar expansion by a factor of ~2-5. Our results show that WR stars can maintain a deep potential well and not expand much while accreting mass at high rates. This allows the formation of an accretion disk and the liberation of large amounts of gravitational energy. Our results strengthen models of intermediate-luminosity optical transients, such as luminous red novae, in which a non-degenerate star accretes at high rates and launches jets that power the transient event.

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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.

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arXiv2025

Natal kick by early-asymmetrical pairs of jets to the neutron star of supernova remnant S147

We analyze the bipolar morphology of the jet-shaped core-collapse supernova (CCSN) remnant (CCSNR) S147 and its neutron star (NS) kick velocity, and suggest that two pairs of unequal, opposite jets contributed to the NS kick velocity. This kick by early asymmetrical pairs (kick-BEAP) of jets mechanism operates within the framework of the jittering jets explosion mechanism (JJEM). We examine the prominent pair of large ears and, based on their flat structure rather than the more common conical structure of ears, conclude that two pairs of jets close in angle inflated the two opposite ears. We connect two opposite X-ray bright zones by an additional axis to create the full point-symmetric morphology of CCSNR S147. We propose that the two unequal jets that formed the X-ray bright zones imparted the first kick-BEAP, while the two pairs of jets that formed the ears imparted the second kick-BEAP. The two kick velocities are of about equal magnitude of ~450 km/s, which implies very energetic jets. Such jets can excite gravitational waves that present detectors can detect from the Galaxy and the Magellanic Clouds. We use the morphology we identify to estimate the CCSNR age at 23,000 yr. Our results strengthen the JJEM.

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arXiv2025

The Puppis A supernova remnant: an early jet-driven neutron star kick followed by jittering jets

We identify a point-symmetric morphology of three pairs of ears/clumps in the core-collapse supernova remnant (CCSNR) Puppis A, supporting the jittering jets explosion mechanism (JJEM). In the JJEM, the three pairs of jets that shaped the three pairs of ears/clumps in Puppis A are part of a large, about 10 to 30 pairs of jets that exploded Puppis A. Some similarities in morphological features between CCSNR Puppis A and three multipolar planetary nebulae considered to have been shaped by jets solidify the claim for shaping by jets. Puppis A has a prominent dipole structure, where one side is bright with a well-defined boundary, while the other is faint and defused. The neutron star (NS) has a natal kick velocity in the opposite direction to the denser part of the dipole structure. We propose a new mechanism in the frame of the JJEM that imparts a natal kick to the NS, the kick-by-early asymmetrical pair (kick-BEAP) mechanism. At the early phase of the explosion process, the NS launches a pair of jets where one jet is much more energetic than the counter jet. The more energetic jet compresses a dense side to the CCSNR, and, by momentum conservation, the NS recoils in the opposite direction. Our study supports the JJEM as the primary explosion mechanism of core-collapse supernovae and enriches this explosion mechanism by introducing the novel kick-BEAP mechanism.

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arXiv2025

Enabling high mass accretion rates onto massive main sequence stars by outer envelope mass removal

Using the one-dimensional numerical code MESA, we simulate mass accretion at very high rates onto massive main sequence stars, M=30, 60, 80 Mo, and find that these stars can accrete up to 10% of their mass without expanding much if we consider a simultaneous mass removal by jets. In this jetted-mass-removal accretion scenario, the accretion is through an accretion disk that launches jets. When the star expands due to rapid mass accretion, it engulfs the inner zones of the accretion disk and the jets it launches. We assume that these jets remove the outer layers of the envelope. We mimic this in the one-dimensional numerical code by alternating mass addition and mass removal parts. We add mass and energy, the accretion energy, to the outer layers of the envelope, leading to rapid stellar expansion. When the star expands by a few tens of percent, we stop mass addition and start mass removal until the star returns to its initial radius. We also show that the density of the accretion disk is larger than the density of the outer layers of the inflated envelope, allowing the disk to launch jets inside the outer inflated envelope layers. Our results show that main sequence stars can accrete mass at high rates while maintaining the deep potential well, as some models of eruptive systems require, e.g., some luminous red novae, the grazing envelope evolution, and the 1837-1856 Great Eruption of Eta Carinae.

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arXiv2025

On the response of massive main sequence stars to mass accretion and outflow at high rates

With a one-dimensional stellar evolution model, we find that massive main-sequence stars can accrete mass at very high mass accretion rates without expanding much if they lose a significant fraction of this mass from their outer layers simultaneously with mass accretion. We assume the accretion process is via an accretion disk that launches powerful jets from its inner zones. These jets remove the outer high-entropy layers of the mass-accreting star. This process operates in a negative feedback cycle, as the jets remove more envelope mass when the star expands. With the one-dimensional model, we mimic the mass removal by jets by alternative mass addition and mass removal phases. For the simulated models of 30Mo and 60Mo, the star does not expand much if we remove more than about half of the added mass in not-too-short episodes. This holds even if we deposit the energy the jets do not carry into the envelope. As the star does not expand much, its gravitational potential well stays deep, and the jets are energetic. These results are relevant to bright transient events of binary systems powered by accretion and the launching of jets, e.g., intermediate luminosity optical transients, including some luminous red novae, the grazing envelope evolution, and the 1837-1856 Great Eruption of Eta Carinae.

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arXiv2024

Identifying a point-symmetric morphology in supernova remnant Cassiopeia A: explosion by jittering jets

We identify a point-symmetric morphology of the supernova remnant (SNR) Cassiopeia A compatible with shaping by at least two, and more likely more than four, pairs of opposite jets, as expected in the jittering jets explosion mechanism (JJEM) of core-collapse supernovae. Using an old Spitzer Telescope infrared map of argon, we identify seven pairs of opposite morphological features that we connect with lines that cross each other at the same point on the plane of the sky. The opposite morphological features include protrusions, clumps, filaments, and funnels in the main SNR shell. In addition to these seven symmetry axes, we find two tentative symmetry axes (lines). These lines form a point-symmetric wind-rose. We place this point-symmetric wind-rose on a new JWST and X-ray images of Cassiopeia A. We find other morphological features and one more symmetry axis that strengthen the identified point-symmetric morphology. Not all symmetry axes correspond to jets; e.g., some clumps are formed by the compression of ejecta between two jet-inflated lobes (bubbles). The robust point-symmetric morphology in the iconic Cassiopeia A SNR strongly supports the JJEM and poses a severe challenge to the neutrino-driven explosion mechanism.

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arXiv2023

The jets and the neutron star kick velocity of the supernova remnant CTB 1

We identify jet-shaped morphology in the core-collapse supernova remnant (SNR) CTB 1 that includes two opposite structural features. We identify these as the imprints of a pair of jets that were among the last jets to explode the massive stellar progenitor of CTB 1. We find the projected angle between the jets' axis and the direction of the pulsar velocity, which is the neutron star natal kick, to be 78 degrees. We tentatively identify possible signatures of a second pair of opposite jets along a different direction. If this identification holds, SNR CTB 1 has a point-symmetric structure. The morphology and large angle of the jets' axis to kick velocity are expected in the jittering jets explosion mechanism (JJEM) of core-collapse supernovae.

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arXiv2023

Wobbling jets in common envelope evolution

We find that the convective motion in the envelopes of red supergiant (RSG) stars supplies a non-negligible stochastic angular momentum to the mass that a secondary star accretes in a common envelope evolution (CEE), such that jets that the secondary star launches wobble. The orbital motion of the secondary star in a CEE and the density gradient in the envelope impose a non-zero angular momentum to the accreted mass with a constant direction parallel to the orbital angular momentum. From one-dimensional stellar evolution simulations with the numerical code \textsc{mesa} we find that the stochastic convection motion in the envelope of RSG stars adds a stochastic angular momentum component with an amplitude that is about 0.1-1 times that of the constant component due to the orbital motion. We mimic a CEE of the RSG star by removing envelope mass at a high rate and by depositing energy into its envelope. The stochastic angular momentum implies that the accretion disk around the secondary star (which we do not simulate), and therefore the jets that it launches, wobble with angles of up to tens of degrees with respect to the orbital angular momentum axis. This wobbling makes it harder for jets to break out from the envelope and can shape small bubbles in the ejecta that compress filaments that appear as arcs in the ejected nebula, i.e., in planetary nebulae when the giant is an asymptotic giant branch star.

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arXiv2023

The core degenerate scenario for the type Ia supernova SN 2020eyj

We argue that the core degenerate (CD) scenario of type Ia supernovae (SNe Ia) can explain the compact helium-rich circumstellar material (CSM) of SN 2020eyj. In the new channel of the CD scenario that we propose there are two major common envelope evolution (CEE) phases. After the white dwarf (WD) companion removes the hydrogen-rich envelope of the asymptotic giant branch star its spiralling-in halts at few solar radii from the core, rather than continuing to the carbon-oxygen (CO) core as in the hydrogen-rich SNe Ia-CSM CD scenario. Only hundreds to tens of thousands of years later, after the helium-rich core expands, does the WD enters a CEE with the helium-rich layer. By that time the hydrogen-rich envelope is at a large distance from the center. The WD merges with the CO core during the second CEE phase, and only after a merger to explosion delay (MED) time of weeks to tens of years the merger remnant explodes. The SN Ia ejecta collides with a helium-rich CSM at tens to hundreds of AU. We follow the evolution of two stellar models with initial masses of 5Mo and 7Mo to their asymptotic giant branch phase when they are supposed to engulf the WD companion. We find that there is a sufficiently massive CO core to merge with the WD in the frame of the CD scenario as well as a massive helium-rich layer, ~0.3-1Mo, to account for the helium-rich CSM of SN 2020eyj.

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arXiv2022

Feeding post core collapse supernova explosion jets with an inflated main sequence companion

We simulate the response of a main sequence star to the explosion of a stripped-envelope (type Ib or Ic) core collapse supernova (CCSN) when the main sequence star orbits the core at a distance of 10-20Ro at explosion. We use the stellar evolution code MESA to follow the response of main sequence stars of masses 3Mo and 7Mo to energy deposition and mass removal. The collision of the CCSN ejecta with the main sequence star deposits energy and inflate the main sequence star. If the binary system stays bound after the CCSN explosion the inflated main sequence star might engulf the newly born neutron star (NS). We assume that the NS accretes mass through an accretion disk and launches jets. The jets remove mass from the inflated main sequence star and collide with the CCSN ejecta. Although this scenario is rare, it adds up to other rare scenarios to further support the notion that many stripped envelope CCSNe are powered by late jets. The late jets can power these CCSNe-I for a long time and might power bumps in their lightcurve. The jets might also shape the inner ejecta to a bipolar morphology. Our results further support suggestions that there are several ways to feed a NS (or a black hole) to launch the late jets in superluminous supernovae.

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arXiv2022

The response of a red supergiant to a common envelope jets supernova (CEJSN) impostor event

Using a one-dimensional stellar evolution code we simulate the response of a red supergiant (RSG) star to injection of energy and to mass removal. We take the values of the energy that we inject and the mass that we remove according to our previous three-dimensional hydrodynamical simulations of a neutron star (NS) on a highly eccentric orbit that enters the envelope of an RSG star for half a year and launches jets as it accretes mass via an accretion disk. We find that for injected energies of ~1e47-1e48 erg and removed mass of ~0.03-0.6Mo the RSG envelope expands to a large radius. Therefore, we expect the NS to continue to orbit inside this massive inflated envelope for several more months, up to about twice the initial RSG radius, to continue to accrete mass and launch jets for a prolonged period. Although these late jets are weaker than the jets that the NS launches while inside the original RSG envelope, the late jets might actually be more influential on the light curve, leading to a long, several months to few years, and bright, about >10^8Lo, transient event. The RSG returns to more or less a relaxed structure after about ten years, and so another transient event might occur in the next periastron passage of the NS. Our results add to the already rich variety of jet-driven explosions/outbursts that might account for many puzzling transient events.

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arXiv2022

Onset of common envelope evolution during a core helium flash by rapid envelope expansion

We suggest that the vigorous core convection during core helium flash on the tip of the red giant branch (RGB) of low mass stars excites waves that carry energy to the envelope and inflate it for few years to increase the number of extreme horizontal branch (EHB; sdB and sdO) stars with masses of ~0.47Mo with respect to canonical binary evolution. Using the open-source MESA-binary we follow the evolution of a number of eccentric binary systems with an initial primary stellar mass of 1.6Mo. The energy that the waves carry to the envelope leads to envelope expansion at the tip of the RGB. The inflated RGB star engulfs many secondary stars to start a CEE that otherwise would not occur. If the secondary star manages to remove most of the RGB envelope the primary evolves to become an EHB star with a mass of ~0.47Mo. However, we expect that in most cases the secondary star does not have time to spiral-in to close orbits. It rather ends at a large orbit and leaves a massive enough envelope for the primary star to later evolve along the asymptotic giant branch and to engulf the secondary star, therefore forming a non-spherical planetary nebula.

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arXiv2022

A rapidly fading star as a type II obscuring intermediate luminosity optical transient (ILOT) in a triple star system

We propose a triple-star scenario where the merger of two pre-main sequence low mass stars, <0.5Mo, ejects a dusty equatorial outflow that obscures and temporarily causes the disappearance of a massive star, >8Mo. The merger of the low-mass inner binary powers a faint outburst, i.e., a faint intermediate luminosity optical transient (ILOT), but its main effect that can last for decades is to (almost) disappear the luminous massive star of the triple system. The typical orbital period of the triple system in about a year. The merger process proceeds as the more massive star of the two low-mass pre-main sequence star starts to transfer mass to the least massive star in the triple system and as a result of that expands. This 'type II obscuring ILOT' scenario in a triple star system might account for the fading, re-brightening, and then re-fading of the massive post-main sequence star M101-OC1. It might recover in about 20-100 year. Our study strengthens the claim that there are alternative scenarios to account for the (almost) disappearing of massive stars, removing the need for failed supernovae. In these scenarios the disappearing is temporary, months to decades, and therefore at later time the massive star explodes as a core collapse supernova even if it forms a black hole.

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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.

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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.

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arXiv2021

A red giant branch common envelope evolution scenario for the exoplanet WD 1856 b

We propose a common envelope evolution (CEE) scenario where a red giant branch (RGB) star engulfs a planet during its core helium flash to explain the puzzling system WD 1856+534 where a planet orbits a white dwarf (WD) of mass 0.52Mo with an orbital period of 1.4 day. At the heart of the scenario is the recently proposed assumption that the vigorous convection that core helium flash of RGB stars drive in the core excite waves that propagate and deposit their energy in the envelope. Using the binary-MESA stellar evolution code we show that this energy deposition substantially reduces the binding energy of the envelope and causes its expansion. We propose that in some cases RGB stars might engulf massive planets of ~0.01Mo during their core helium flash phase, and that the planet can unbind most of the mass of the bloated envelope. We show that there is a large range of initial orbital radii for which this scenario might take place under our assumptions. This scenario is relevant to other systems of close sub-stellar objects orbiting white dwarfs, like the brown dwarf-WD system ZTFJ003855.0+203025.5.

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arXiv2021

The future influence of six exoplanets on the envelope properties of their parent stars on the giant branches

We study the evolution of six exoplanetary systems with the stellar evolutionary code MESA and conclude that they will likely spin-up the envelope of their parent stars on the red giant branch (RGB) or later on the asymptotic giant branch (AGB) to the degree that the mass loss process might become non-spherical. We choose six observed exoplanetary systems where the semi-major axis is ~1-2AU, and use the binary mode of MESA to follow the evolution of the systems. In four systems the star engulfs the planet on the RGB, and in two systems on the AGB, and the systems enter a common envelope evolution (CEE). In two systems where the exoplanet masses are Mp~10MJ, where MJ is Jupiter mass, the planet spins-up the envelope to about 10% of the break-up velocity. Such envelopes are likely to have significant non-spherical mass loss geometry. In the other four systems where Mp~MJ the planet spins-up the envelope to values of ~1-2% of break-up velocity. Magnetic activity in the envelope that influences dust formation might lead to a small departure from spherical mass loss even in these cases. In the two cases of CEE on the AGB the planet deposits energy to the envelope that amounts to >10% of the envelope binding energy. We expect this to cause a non-spherical mass loss that will shape an elliptical planetary nebula in each case.

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