Jittering jets in stripped-envelope core-collapse supernovae

arXiv:2510.02203 · astro-ph.HE, astro-ph.SR · Submitted 2025-10-02 · Read on arXiv

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Introduction to the show: ident: Astrophysics Radio. Generated commentary on the latest astrophysics papers.

Vera: Today's paper: "Jittering jets in stripped-envelope core-collapse supernovae".

Jocelyn: The gist The study finds that all models in the initial mass range of MZAMS = 12M⊙ to MZAMS = 40M⊙, regardless of whether they have hydrogenrich, hydrogen-stripped,

Vera: First, who's behind it and why it matters.

Title and authors: Jocelyn: Moving on to the summary of "Jittering jets in stripped-envelope core-collapse supernovae." This paper really zeroes in on those pre-collapse convective and velocity fluctuations we discussed, specifically in progenitors that have lost most of their hydrogen and helium.

Subrahmanyan: It’s important to remember they are focusing on the stripped-envelope CCSN progenitors because that’s where the physics gets interesting for the JJEM, as earlier studies hadn't fully explored this area.

Vera: The summary is basically reiterating that in all their tested models, regardless of whether they started with a hydrogenrich envelope or an H stripped envelope or a He plus hydrogen stripped envelope, there is at least one significant strong convective zone in the inner core.

Jocelyn: So it’s not just for some specific initial conditions; it’s a general feature across the mass range from MZAMS = 12Msun to MZAMS = 40Msun <ref:2510.02203#pg1>.

Subrahmanyan: That broad coverage is what makes this result relevant for structure formation, because it suggests that core physics in these massive stars is consistently leading toward a specific type of explosion pathway.

Vera: They also emphasize how the lower overall mass in stripped-envelope models leads to lower densities and temperatures in the outer core layers, which results in less complete burning of the Si plus S layers at the onset of collapse.

Jocelyn: And they point out that because these gradients are steeper near the core’s edge, they end up being more prone to convection, which is what drives those fluctuations.

Subrahmanyan: So we have a chain here: stripping leads to different density profiles, which leads to steeper gradients, and that steep gradient triggers the robust inner core convection that feeds the JJEM.

Vera: And they also looked at angular momentum seed perturbations using the specific angular momentum parameter j equals vconv, where r is the radius of the layer and vconv is the convective velocity according to mixing length theory.

Jocelyn: That specific parameter j equals vconv is what they are using to quantify those fluctuations, and they found that in all models except for MZAMS = 40Msun with H plus He removed envelope, there is at least one layer with j greater than or equal to two times ten to the power of fifteen centimeters squared per second inside the mass coordinate that forms a neutron star.

Subrahmanyan: That threshold, that two times ten to the power of fifteen centimeters squared per second, is what they identify as being large enough j(m) for these inner convective zones to facilitate the JJEM.

Vera: They also looked at how this moves things around; in massive envelope-removed stars, the inner convective zones with large enough j equals vconv to facilitate the JJEM tend to move toward lower mass coordinates.

Jocelyn: So as you strip more material, those crucial angular momentum seed perturbations are being pushed into regions closer to where a neutron star forms.

Subrahmanyan: That’s a key result because it shows how the core structure is evolving dynamically in response to the progenitor evolution, which is something we need to keep an eye on for structure formation.

The paper's summary: Vera: Now let’s talk about what this paper suggests as improvements or next steps for the study of "Jittering jets in stripped-envelope core-collapse supernovae." The authors are pointing out several things they think we need to do next.

Jocelyn: They highlight that the current numerical codes can’t resolve the small scale magnetic field reconnection, and they can't simulate the JJEM directly because of that.

Subrahmanyan: That’s a big limitation, because simulating those jets requires resolving very small-scale physics, which is what limits our tools right now for studying the source of angular momentum in intermittent accretion disks.

Vera: So they are essentially saying that simulations for the powering of the explosion and the shaping of the ejecta, like those done by Papish and Soker or Akashi and Soker or Abdikamalov and Beniamini, differ from the tools used to study angular momentum in intermittent accretion disks.

Jocelyn: They suggest that some JJEM studies focus on demonstrating that pre-collapse core convection zones exhibit large fluctuations in both velocity and angular momentum, which are characterized by significant variations in magnitude and direction.

Subrahmanyan: And those fluctuations are amplified by instabilities above the neutron star, for example, Abdikamalov et al. or Kazeroni and Abdikamalov or Buellet et al.

Vera: So the paper points toward needing more sophisticated modeling of those instabilities above the NS to fully amplify these stochastic angular momentum fluctuations before they seed any accretion disks.

Jocelyn: That seems like a logical next step, because if you can model that amplification better, maybe you can start to see those intermittent accretion disks forming.

Subrahmanyan: And if those disks form, then the whole picture of the explosion mechanism shifts toward something more complex than just a simple jet launch.

The paper's improvements: Vera: So to wrap up our discussion on this paper, we’ve established that there is at least one significant strong convective zone in the inner core for all models in the initial mass range of MZAMS = 12Msun to MZAMS = 40Msun, regardless of whether they have hydrogenrich, hydrogen-stripped, or helium plus hydrogen stripped envelopes <ref:2510.02203#pg1,at least one significant strong convective zone in the inner core>.

Jocelyn: And we’ve seen that this convection is robust and it facilitates the JJEM by showing a significant angular momentum parameter j equals vconv greater than or equal to two times ten to the power of fifteen centimeters squared per second inside the mass coordinate that forms a neutron star.

Subrahmanyan: The implication is that according to this study on "Jittering jets in stripped-envelope core-collapse supernovae," there is at least one significant strong convective zone in the inner core for all models, which can facilitate the JJEM.

Vera: This result strengthens the claim that according to the JJEM, there are no failed CCSNe and that all massive stars explode.

Jocelyn: It’s a small step toward showing those intermittent accretion disks might actually forming, even though they don't show them yet in this specific work.

Subrahmanyan: It’s a strong piece of evidence for the JJEM, but it doesn't prove that the intermittent accretion disks are actually forming yet.

Vera: We’ve examined the paper "Jittering jets in stripped-envelope core-collapse supernovae" and found that this robust convection is present and sufficient to seed perturbations for the JJEM.

Jocelyn: That’s a small step in demonstrating the robust convection in the inner core of stripped-envelope CCSN progenitors.

Subrahmanyan: It’s progress in establishing the JJEM as a primary explosion mechanism, but it doesn't show that those intermittent accretion disks actually form yet.

Vera: We have done our part with this paper on "Jittering jets in stripped-envelope core-collapse supernovae."

Conclusion: Vera: So we’ve been looking at "Jittering jets in stripped-envelope core-collapse supernovae," and the main thing here is that they found there’s at least one significant strong convective zone in the inner core for all models, from MZAMS = 12Msun up to MZAMS = 40Msun <ref:2510.02203#pg1,at least one significant strong convective zone in the inner core>.

Jocelyn: Right, so regardless of whether you stripped hydrogen or both hydrogen and helium off these stars, that convection feature is there.

Subrahmanyan: That’s what they found in all models, which is important because it suggests this core physics keeps happening across that whole mass range.

Vera: And they linked that convection to the jittering-jets explosion mechanism by finding a specific angular momentum parameter j equals vconv greater than or equal to two times ten to the power of fifteen centimeters squared per second inside the mass coordinate that forms a neutron star.

Jocelyn: Two times ten to the power of fifteen, that’s what they are using as their threshold for what’s needed to facilitate those jet launches.

Subrahmanyan: That specific number is what they identified as being large enough j(m) for the inner convective zones to facilitate the JJEM.

Vera: They also looked at how this angular momentum moves, and they saw that in massive envelope-removed stars, those inner convective zones with that large j equals vconv tend to move toward lower mass coordinates.

Jocelyn: So as you strip more material off these progenitors, the critical angular momentum seed perturbations are being pushed into regions closer to where a neutron star forms.

Subrahmanyan: That’s a key result because it shows how the core structure is evolving dynamically in response to progenitor evolution, which is something we need to keep an eye on for structure formation.

Vera: The implication for us observing this stuff is that according to the JJEM, there are no failed CCSNe and that all massive stars explode.

Jocelyn: That’s a strong claim based on their findings in "Jittering jets in stripped-envelope core-collapse supernovae."

Subrahmanyan: It’s progress in establishing the JJEM as a primary explosion mechanism, but it doesn't show that those intermittent accretion disks actually form yet.

Vera: They did do examine the timing of the processes, and they found that the Fe/Si interface is accreted about zero point one to zero point three seconds before the Si/O interface in most models.

Jocelyn: So those convective regions, including that Fe/Si interface and Si/O interface, are all accreted before the neutrino-driven mechanism revives the stalled shock.

Subrahmanyan: That’s a crucial comparison for differentiating between two different explosion mechanisms.

Vera: It’s a small step toward showing those intermittent accretion disks might actually forming, even though they don't show them yet in this specific work.

Jocelyn: So it’s a good piece of evidence for the JJEM, but it doesn't show that the intermittent accretion disks are actually forming yet.

Subrahmanyan: We should look at how those instabilities above the neutron star amplify those initial perturbations to see if we can get a better picture of those disks.

Vera: That’s what we’re going to look at next, so keep an eye on that amplification process.

Department of Physics, Technion - Israel Institute of Technology

astro-ph.HE, astro-ph.SR

Submitted: 2025-10-02

Updated: 2026-10-14

Comments: Accepted for publication in ApJ

License: http://creativecommons.org/licenses/by/4.0/

Importance score: 81/100

The gist: The gist The study finds that all models in the initial mass range of MZAMS = 12M⊙ to MZAMS = 40M⊙, regardless of whether they have hydrogenrich, hydrogen-stripped, or helium+hydrogen-stripped

Key concepts

Jittering Jets Explosion Mechanism (JJEM)
This mechanism suggests that convection within the core seeds angular momentum perturbations. These perturbations lead to instabilities that form intermittent accretion disks, which then launch pairs of jittering jets capable of exploding the star. The study investigates if these necessary convective zones exist in stripped-envelope progenitors.
Stripped-Envelope Core-Collapse Supernovae (SECCSNe)
These are models of stars that have lost most or all of their outer hydrogen and helium envelopes before collapsing into a neutron star. The researchers specifically examined these models because they are relevant to the conditions where the JJEM might operate.
Specific Angular Momentum Parameter ($j = v_{ ext{convr}}$)
This parameter measures the specific angular momentum within a stellar layer, calculated based on its convective velocity. The study analyzed this value in the core layers of pre-collapse stars to identify zones with sufficient angular momentum needed to facilitate the formation of accretion disks for the JJEM.
Neutrino-Driven Mechanism
This is a standard theoretical model for supernova explosions where energy and momentum are supplied by neutrinos streaming out from the hot proto-neutron star. The study compares the timing of jet accretion with this mechanism's shock revival to show that jets can operate before neutrino heating fully succeeds.

Terminology

Summary

The gist The study finds that all models in the initial mass range of MZAMS = 12M⊙ to MZAMS = 40M⊙, regardless of whether they have hydrogenrich, hydrogen-stripped, or helium+hydrogen-stripped envelopes, have at least one significant strong convective zone in the inner core, which can facilitate the jittering-jets explosion mechanism (JJEM)

Model Setup and Stripping Scenarios

The researchers used the one-dimensional stellar evolution code mesa to model five different masses of SECCSNe, ranging from MZAMS = 12M⊙ up to MZAMS = 40M⊙. For each mass, three scenarios of envelope stripping were simulated: a regular wind that leaves a hydrogenrich envelope at the explosion (“full envelope”), evolution that includes an extra mass loss that removes the hydrogen but leaves helium (“H-stripped envelope”), and the removal of both hydrogen and helium (“Hestripped envelope”). They used default controls in the ‘20M pre ms to core collapse’ test suite, including the Ledoux criterion with mixing length theory (MLT) coefficient αMLT = 1.5 and semi-convection coefficient αSC = 0.01. The envelope removal was done using ‘relax initial mass to remove H env’ and a similar handle ‘relax initial mass to remove He env’, where the latter is implemented directly into the mesa code.

Convection in Stripped Envelope Progenitors

The study examined pre-collapse convective and velocity fluctuations in progenitors that have lost most of their hydrogen and helium, specifically SECCSNe. In Figure 1, they present the composition and some other stellar properties of two models, MZAMS = 12M⊙ and MZAMS = 28M⊙, for the three envelope compositions at the onset of core collapse. The presence of strong convection in the Fe/Si interface and the inner oxygen layer is shown in all models, mass coordinates that correspond to the formation of an NS. In stripped-envelope models, lower overall mass results in lower densities and temperatures in the outer core layers, which leads to less complete burning of the Si+S layers at the onset of collapse. Additionally, the temperature and composition gradients near the core’s edge are generally steeper, causing higher opacity in the outer regions of stripped-envelope models and making them more prone to convection.

Angular Momentum Parameter Analysis

The study aimed to examine angular momentum seed perturbations in the pre-collapse core using the specific angular momentum parameter j = vconvr. In all simulated models except for the MZAMS = 40M⊙ with H+He removed envelope, there is at least one layer with j > 2 × 1015 cm2 s−1 inside the mass coordinate that forms a NS. The relevant zones for NS formation are those inward to the maximum baryonic mass for the formation of a NS, m ≃ 2.65 M⊙. The main conclusion from Figures 3, 4, and Appendix D is that in massive envelope-removed stars, the inner convective zones with large enough j(m) to facilitate the JJEM tend to move to lower mass coordinates.

Explosion Timescale Comparison

The explosion according to the JJEM starts when the newly born NS accretes the convective layers from the core, generally near the Fe/Si interface and Si/O interface. The study compares this time with shock revival times in neutrino-driven simulations, finding that in most models, the accretion of the Si/O interface occurs before shock revival. The Fe/Si interface is accreted ≃ 0.1 − 0.3 s before the Si/O interface in most models. This suggests that the convective regions, including the Fe/Si interface and Si/O interface, are accreted before the neutrino-driven mechanism revives the stalled shock.

Conclusion on Explosion Mechanism

The main conclusion is that there is at least one significant strong convective zone in the inner core for all models, which can facilitate the JJEM. This finding is encouraging for the JJEM, although it does not show that the intermittent accretion disks indeed form. The study strengthens the claim that, according to the JJEM, there are no failed CCSNe and that all massive stars explode. The presence of convective layers in the inner core, for mass coordinates that form an NS, is robust. Most models have a specific angular momentum parameter of j(m) > 2.5×1015 in the inner core. This finding is encouraging for the JJEM, although it does not show that the intermittent accretion disks indeed form. The study represents a small step in demonstrating the robust convection in the inner core of stripped-envelope CCSN progenitors.

How it works

  1. The models are simulated using mesa to cover initial masses from MZAMS = 12M⊙ to MZAMS = 40M⊙, with three stripping scenarios: full envelope, H-stripped envelope, and Hestripped envelope.

  2. Convection is analyzed by examining the specific angular momentum parameter j(m) = rvconv, finding at least one layer with j(m) ≳ 2 × 1015 cm2 s−1 inside the mass coordinate that is the maximum baryonic mass of a neutron star, m ≃ 2.65 M⊙.

  3. The JJEM posits that convection in these zones seeds instabilities above the newly born NS, leading to the formation of intermittent accretion disks that launch pairs of jittering jets, which in turn explode the star.

  4. The study found that convective regions, the Fe/Si interface in the majority (and possibly all) cases, and the Si/O interface are accreted before shock revival.

Summary

The JJEM asserts that pre-core-collapse convection seeds the angular momentum perturbations that form the intermittent accretion disks that launch the jittering pairs of jets that explode CCSNe. The shaping of CCSNRs by two or more pairs of jets is a robust finding of the last two years. Using the onedimensional stellar code mesa, including no magnetic fields or rotation, they examined the specific angular momentum parameter j(m) in the cores of pre-collapse stellar models, focusing on stripped-envelope stars. Their main results indicate that in all models, regardless of whether they have hydrogenrich, hydrogen-stripped, or helium+hydrogen-stripped envelopes, there is at least one significant strong convective zone in the inner core. This finding is encouraging for the JJEM, although it does not show that the intermittent accretion disks indeed form. The study strengthens the claim that, according to the JJEM, there are no failed CCSNe and that all massive stars explode. The progress in establishing the JJEM as the primary explosion mechanism of CCSNe has been made in many small steps.

How it works

The study focused on stripped-envelope CCSNe (SECCSNe) to examine pre-collapse convective and velocity fluctuations. They found that convection is robust in the inner core, and the convective zones are sufficient to facilitate the JJEM. The angular momentum parameter analysis showed that in massive envelope-removed stars, the inner convective zones with large enough j(m) to facilitate the JJEM tend to move to lower mass coordinates.

Summary

The study examined pre-collapse convective and velocity fluctuations in progenitors that have lost most of their hydrogen and helium, specifically stripped-envelope CCSNe. The main results are the red areas in Figures 3, 4, and Appendix D. These results indicate that in all models, regardless of whether they have hydrogenrich, hydrogen-stripped, or helium+hydrogen-stripped envelopes, there is at least one significant strong convective zone in the inner core. By inner core, they refer to the core inside the mass coordinate that is the maximum baryonic mass of a NS. Their finding is encouraging for the JJEM, although it does not show that the intermittent accretion disks indeed form. In this theoretical study, they examined convective motion according to the mixing length theory (MLT) as implemented in mesa. Three-dimensional simulations reveal that the maximum convection velocity in three dimensions is several times faster than the velocity that the MLT gives, particularly for low angular wavenumbers.

How it works

The study compared the time at which a stalled shock starts to re-expand and the time of Si/O interface accretion to elaborate on the relation between two explosion mechanisms. They found that in most of their models, the Fe/Si is accreted before the Si/O interface. The convective regions, the Fe/Si interface in the majority (and possibly all) cases, and the Si/O interface are accreted before the neutrino-driven mechanism revives the stalled shock.

Improvements for AI systems

  1. AI systems can predict CCSN remnant morphologies by analyzing core convection, as the point-symmetric morphology is only property that decisively distinguishes between the predictions of the JJEM and the neutrino-driven mechanism. This allows AI to classify observed supernova remnants into predicted explosion mechanisms based on their shape.

  2. AI models can assess progenitor suitability for jet-driven explosions by calculating the specific angular momentum parameter, as "in all simulated models except for the MZAMS = 40M⊙ with H+He removed envelope, there is at least one layer with j(m) > 2 × 1015 cm2 s−1 inside the mass coordinate that forms a NS." This helps in filtering massive stars to identify those most likely to explode via JJEM.

  3. AI systems can determine the timing of explosion mechanisms by comparing accretion timescales, as the Fe/Si interface is accreted ≃ 0.1 − 0.3 s before the Si/O interface in most models. This capability enables AI to differentiate between the JJEM and the neutrino-driven mechanism based on which process starts operating first.

  4. AI can identify robust features that facilitate jet launching, as the pre-collapse envelope convection is robust, and that this convection is sufficient to seed perturbations for the JJEM, as suggested by Sato et al. (2025). This allows AI to confirm the presence of necessary physical conditions for a successful explosion.

  5. AI can predict black hole formation scenarios based on core rotation, as black holes are formed when the pre-collapsed core is rapidly rotating, enabling it to distinguish between a failed supernova and an energetic explosion, even when a black hole forms.

Abstract

We compare the expected explosion time of core-collapse supernovae (CCSNe) in the jittering jets explosion mechanism (JJEM) to that in the neutrino-driven (the delayed neutrino) mechanism, and conclude that for most, but not all, stellar models, even when the neutrino-driven mechanism might have led to an explosion, the JJEM starts to operate before the neutrino mechanism fully revives the stalled shock. To achieve this goal, we conduct comprehensive one-dimensional stellar evolution simulations using the code mesa to determine the expected explosion time according to the JJEM, which corresponds to the time when the inner convective layer of the core is accreted onto the newly born neutron star (NS). We present results for many hydrogen-rich, hydrogen-stripped, and helium+hydrogen-stripped envelope CCSN progenitor models. We find that most, but not all, of our models in the initial mass range of M ZAMS=12M to M ZAMS=40M, have at least one strong convective zone inside the mass coordinate that is the maximum baryonic mass of an NS, m 2.65 M, which can facilitate the JJEM. This study contributes to establishing the JJEM as a viable explosion mechanism of CCSNe.

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