Multiple shells in supernova 2023ixf support the jittering jets explosion mechanism (JJEM)

TL;DR

SN 2023ixf is analyzed to test the jittering jets explosion mechanism (JJEM) against the delayed neutrino mechanism. By fitting the photospheric radius evolution, the authors identify two or three ejecta shells with distinct, nearly ballistic expansion, consistent with consecutive jet activity. They further show that several CCSN remnants exhibit two or more shells—full or partial—anatomical footprints of jet-driven explosions, supported by recent 3D hydrodynamic simulations. Collectively, the results strengthen JJEM as a major CCSN explosion pathway and emphasize shell structure as a diagnostic for jet activity in both the photospheric phase and remnants.

Abstract

Examining the photospheric time evolution of the core-collapse supernova (CCSN) SN 2023ixf from the literature, we identify two (possibly three) evolutionary time periods with constant expansion velocities, which we attribute to two (or three) ejecta shells. We find that several CCSN remnants have morphologies with two or more complete or partial shells, compatible with the presence of two (or three) photospheric shells during the photospheric phase of the explosion. Studies have attributed these CCSN remnants to the jittering-jet explosion mechanism (JJEM), which involves two or three energetic pairs of jets participating in the explosion. We, therefore, conclude that the structure of the photospheric shells of SN 2023ixf supports its explosion by the JJEM. This study adds to the accumulating evidence that the JJEM is the primary explosion mechanism of CCSNe.

Figures (4)

• Figure 1: The time evolution of the photospheric radius from Zimmermanetal2024 based on photometry (not on spectroscopy). We fit two straight lines through two groups of points: the first four points, green stars, at $t= 1.13-1.42 ~\rm{day}$ that we mark as Shell 1, and the next 11 points, green pentagons, at $t= 1.57-6.13 ~\rm{day}$ that we mark as Shell 2. The red pentagons are excluded from the fitting; they belong to the phase when the photosphere is moving inward in the mass coordinate of the ejecta. We also indicate the velocity of each shell during the fitting period. The line for Shell 3 fits a later time period, as shown in Figure \ref{['fig:Graph2']}. We identify these shells as photospheric shells appearing one after the other. The straight lines for the three shells are $R_{\rm ph1}= 1.050t +0.425$, $R_{\rm ph2}= 0.808t +0.477$, and $R_{\rm ph3}= 0.445t +0.723$, where the time is in days and the radius in units of $10^{14} ~\rm{cm}$. All lines have a coefficient of determination (R-Squared) of $R^2=0.98$. The velocities and their uncertainties are from fitting the ejecta photosphere radii without including the radii of the shells at $t=0$. Including the radii at $t=0$ changes the velocities little but substantially reduces the uncertainties, indicating that the three shells are distinct, by these photospheric radii (caveat: see text on the possibility that Shells 1 and 2 are a single shell).
• Figure 2: Similar to Figure \ref{['fig:Graph1']}, but including later times, and different scales on the axes. As in Figure \ref{['fig:Graph1']}, red pentagons and pluses are excluded from fittings. We fit a third straight line to the points in the time period of $t= 42.19-70.63 ~\rm{day}$ (green pluses); this is Shell 3. The points from day 7 to day 41 (red pentagons) are the photospheric radius in the ejecta inward to Shell 2 and outside Shell 3. During that time, the photosphere moves inward in the mass coordinate of the ejecta. Therefore, each point corresponds to a deeper mass layer than the previous point; the points do not represent a single layer. For that, we cannot fit a straight line through these points. Around day 45, the front of Shell 3 becomes the photosphere. From there to about day 71, a straight line corresponds to the front of Shell 3. After day 71, Shell 3 became transparent, and the photosphere moved inward in the mass coordinate of the ejecta (red pluses).
• Figure 3: Two images of CCSN remnants with two full (or almost full) shells (but not spherical). Studies attributed their morphologies to the JJEM. In each image, we marked the two prominent shells that can form two photospheric shells one after the other during the photospheric phase of such CCSNe; the arrows point to only four points on the projection of each shell boundary onto the plane of the sky. Filled double-lined arrows point at the first shell, and the empty double-lined double-headed arrows point at the second shell. (a) A radio image of SNR G309.2–00.6 adapted from Gaensleretal1998, who already argued that jets shaped this CCSN. The rim-nozzle symmetry marks are from Soker2024PNSN. (b) A composite image of CCSNR W44 from https://www.nasa.gov/universe/nasas-fermi-proves-supernova-remnants-produce-cosmic-rays/. Soker2024W44 added the two double-headed arrows that depict the two axes of the two energetic pairs of jets that participated in the explosion of W44. Magenta: GeV gamma-ray from Fermi’s LAT; yellow: Radio from the Karl G. Jansky Very Large Array; Red: infrared; Blue: X-ray from ROSAT. Credit: NASA/DOE/Fermi LAT Collaboration, NRAO/AUI, JPL-Caltech, ROSAT.
• Figure 4: Two images of CCSNRs where at least one shell is partial. (a) A MeerKat radio image at 1.28 GHz of SNR G0.9+0.1 adapted from MeerKAT2022. The inset on the upper left is a desaturated image of the pulsar wind nebula. Soker2025G0901 added the pale-blue marks of structural features used to identify the point-symmetric morphology. For a line of sight along the large ear in the north, the three shells (their projection on the plane of the sky forms the rims) might form three photospheric shells. The first two (pointed at by the solid one-head yellow arrow and double-lined double-headed yellow arrow) are partial. The third shell (pointed at by the three-headed arrow) is the main shell of the SNR. (b) A Chandra X-ray image of N63A (red, green, blue for different X-ray energy bands); see also Karagozetal2023. Soker2024CounterJet added the three red lines between the tips of opposite ears to mark the symmetry axis of three pairs of jets that participated in the explosion of this point-symmetric CCSNR. Each ear's front can form the first photospheric shell, depending on the viewing angle. The main CCSNR forms the next photospheric radius. The light brown region to the upper right of the three red lines is optical light detected by Hubble. (Credit: Enhanced Image by Judy Schmidt based on images provided courtesy of NASA/CXC/SAO & NASA/STScI.)