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

TL;DR

The paper argues that Circinus X-1’s ring structures result from very late, oppositely directed jets launched during the core-collapse explosion, consistent with the jittering jets explosion mechanism (JJEM). It links Cir X-1’s Africa Nebula morphology to jet-shell interactions and compares it to rings in remnants like the Cygnus Loop, supporting JJEM as a robust framework for jet-shaped CCSNRs. Three-dimensional simulations demonstrate the feasibility of ring formation by late jets, and the authors discuss how jet-induced kicks can be compatible with Cir X-1’s observed slow proper motion and bound binary. The study strengthens the case for jet-driven CCSN explosions and provides a path to interpret rings and ears in multiple remnants, while noting limitations and directions for more detailed modeling.

Abstract

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.

Figures (5)

• Figure 1: A figure adapted from Gasealahweetal2025, showing a radio MeerKAT L band image of the Cir X-1 nebula, termed the Africa Nebula. Black labeling is from Gasealahweetal2025 and red from this study; we term their bubbles ears, and define the plume and the blowout.
• Figure 2: Comparing the Africa Nebula to two other CCSNRs. (a+b) Images of the Africa Nebula adapted from Gasealahweetal2025. We added all marks: in yellow, features discussed by Gasealahweetal2025; and in red, orange, and pale blue, our new definitions. (a) Three sub-bands of the radio continuum observations by colors. We identify four broken rims (BR). (b) A map combining spectral index (by color according to the color bar) and intensity (by brightness). Double-lined arrows schematically represent our suggestion for energetic exploding jets. (c+d) Images of CCSNR Cygnus Loop adapted from ShishkinKayeSoker2024, with all marks from ShishkinKayeSoker2024. (c) GALEX UV image in 175 - 280 nm (GALEX2007; Credit: NASA/JPL-Caltech). (d) Magenta represents visible, green represents log scale X-ray, and teal represents the AKARI $90 \mu m$ image. (e+f) A MeerKat radio image at 1.28 GHz of SNR G0.9+0.1 adapted from MeerKAT2022 with all marks from Soker2025G0901. (e) The inset on the upper left is a desaturated image of the pulsar wind nebula. (f) The inset is an image from Camiloetal2009, which reported the discovery of the pulsar indicated by the yellow dot. Soker2025G0901 marked by the dashed pale blue and the green-dotted two-sided arrows axes of two pairs of jets, he suggested to be the main-jet axis of SNR G0.9+0.1, and by two-sided double-lined red arrows, two additional symmetry axes he attributed to pairs of exploding jets.
• Figure 3: An image of a supernova remnant candidate G107.7-5.1 adapted from Fesenetal2024, with the identified structural features of a bubble, a nozzle, and three rims (in blue) from Soker2024CF. We identify a possible ring, through which we draw one symmetry axis shaped by two energetic pairs of jets. We suggest a second symmetry axis from Rim 1 to the nozzle.
• Figure 4: A visible-band image of the Cygnus Loop CCSNR adapted from Raymondetal2023 with marks in white from ShishkinKayeSoker2024, and our specific identification of the ring (only part of which is observed), which they used to define the cavity. The three long white lines mark the claim by ShishkinKayeSoker2024 for three pairs of energetic jets that participated in the explosion of the Cygnus Loop.
• Figure 5: Scaled emission integral maps of three simulations. The scaled emission integral is the integral of the square of the density along the line of sight, $\int \rho^2 d Y_s$, and it mimics observations. Each simulation shows the formation of two opposing rings produced by two unequal jets at the final phase of the explosion. In each panel, we record the time at which the simulation was terminated, the energy of each jet in units of $10^{51} ~\rm{erg}$, and its half-opening angle in degrees. In all cases, the axis of the two jets is inclined at $75^\circ$ to the line of sight. The coordinates on the plane of the sky are $X_s$, which coincides with the grid's $x$-axis, and $Z_s$, which is in the grid's $yz$ plane and at $15^\circ$ to the $z$ axis (the jets' axis). The color bar of the upper two panels is in units of a $10^{17}\ \mathrm{g}^2\mathrm{cm}^{-5}$, while the color bar of the third panel is in units of $10^{16}\ \mathrm{g}^2\mathrm{cm}^{-5}$.