Luminous Late-time Radio Emission from Supernovae Interacting with Circumbinary Material

TL;DR

This work confronts the origin of luminous late-time radio emission in hydrogen-poor core-collapse SNe by linking binary evolution with circumbinary material to ejecta-CSM interaction. A forward-modeling framework combines MESA-based binary evolution of stripped-envelope donors with a dynamical ejecta-CSM interaction model and a synchrotron radiative transfer calculation, producing radio light curves that incorporate SSA and FFA. The study shows that dense CSM produced by non-conservative mass transfer, whether as detached shells for low-mass donors or wind-like for higher-mass donors, can yield late-time radio luminosities in the range $L_\nu \sim 10^{27}$–$10^{29}$ erg s$^{-1}$ Hz$^{-1}$ during years to decades after explosion, comparable to observations; however, explaining early-time radio data requires additional CSM complexity such as faster ejection or a two-component CSM with varied geometry and viewing angles. Overall, the results support binary interaction as a viable mechanism for dense CSM around stripped-envelope SN progenitors and provide a flexible framework to explore alternative binary scenarios and multi-wavelength signatures.

Abstract

Numerous core-collapse supernovae (CCSNe) exhibit signatures of interaction with circumstellar material (CSM). Bright radio emission years after the SN is one such indication of dense CSM at large distances from the star, which may be generated via binary interactions. In this work, we use forward modeling to study the radio emission produced by interaction between the SN ejecta and CSM formed by non-conservative stable mass transfer from stripped-envelope stars in short-period binaries. The donors are among the likely progenitors of hydrogen-poor CCSNe that significantly expand $10^3$-$10^4$ years before core-collapse, with companions that best represent low-mass compact objects. We identify that non-conservative stable mass transfer from lower-mass stripped stars can create a detached shell-like CSM, whereas for our higher-mass stars the CSM is wind-like. In our models, mass transfer rates of $\sim 10^{-4} M_\odot$ $\mathrm{yr}^{-1}$ lead to dense CSM extending to $\sim 10^{18}$ $\mathrm{cm}$. The predicted radio emission is luminous at late times, reaching $L_ν\sim10^{26}$-$10^{29}\mathrm{erg}$ $\mathrm{s}^{-1}\mathrm{Hz}^{-1}$ at years to decades after core-collapse, which is as bright as late-time radio emission observed for a sample of hydrogen-poor SNe. However, the light curves of events with early-time data show more complex behavior in the weeks to months after core-collapse. We qualitatively demonstrate that similar early-time emission can manifest for CSM that is accelerated to speeds of $\sim10^3$ $\mathrm{km}$ $\mathrm{s}^{-1}$ upon ejection, as well as for different viewing angles in case of an asymmetric CSM distribution.

Figures (5)

• Figure 1: Left: The mass loss history of the stripped star models listed in Table \ref{['tab:hestarmodels']}, shown as the mass transfer rate of the donor star as a function of time until core collapse. Right: Density profiles of the CSM for the stripped star models listed in Table \ref{['tab:hestarmodels']}, shown for parameters $v_{\rm CSM} = 0.3\, v_{\mathrm{orb},c}$ and $f_{\Omega}=1$. The dotted line shows a wind profile CSM for a mass-loss rate $10^{-5}\ M_\odot\ {\rm yr}^{-1}$ and velocity of $10^{3}~\mathrm{km}\ \mathrm{s}^{-1}$, typically observed in Wolf-Rayet stars. The gray shaded region is taken from Figure 7 of Maeda22 and represents the range of CSM density distributions derived for SNe Ibn in that work.
• Figure 2: Light curves of radio emission at 3 GHz for the models listed in the legend of the second panel from the top. Each is calculated using the values of $f_{\Omega}$, $\epsilon_B$, and $\epsilon_E$ listed in the upper right of each panel. The solid lines represent the light curves for models assuming a kinetic energy of $E_{\rm ej} = 10^{51}$ erg. The shaded regions represent the range of emitted flux between $E_{\rm ej} = 5\times10^{50}$ erg and $E_{\rm ej} = 1.5\times10^{51}$ erg, with lower luminosities for smaller $E_{\rm ej}$. Scatter points represent observed late-time radio emission from a sample of events listed in the legend of the top panel, taken from Stroh21.
• Figure 3: Light curves of radio emission at 15 GHz for the same models as in Figure \ref{['fig:allmodels_latetime']}. Scatter points show observed radio emission at $\approx15$ GHz for the events listed.
• Figure 4: Top row: Light curves of radio emission at 3 GHz for the models listed in the legend. Each is calculated with $E_{\rm ej}=10^{51}$ erg and the parameters listed in the upper right of each panel. The solid lines show the light curve for a CSM velocity of $0.3\, v_{\rm orb, c}$, as in Figure \ref{['fig:allmodels_latetime']}. The dotted lines show the light curve for a fast CSM of $10^3~\mathrm{km}\ \mathrm{s}^{-1}$, assuming the CSM has been accelerated by some mechanism upon ejection from the binary system. The scatter points represent the same events as listed in the legend of Figure \ref{['fig:allmodels_latetime']}. Bottom row: Light curves of radio emission at 15 GHz for the same models as in the top row. The scatter points represent the same events as listed in the top right legend of Figure \ref{['fig:allmodels_earlytime']}.
• Figure 5: Top row: Light curves of radio emission at 3 GHz for the models listed in the legend. Each is calculated with $E_{\rm ej}=10^{51}$ erg and the parameters listed in the upper right of each panel. The solid lines show an estimate of the light curve for a face-on viewing angle, which is the sum of contributions from the low-density stellar wind in the polar regions and from the dense CSM in the torus. The early peaks appear due to the low-density stellar wind (dotted line), and the second bright peak is set by SSA for the CSM. The dashed lines show the light curve from an edge-on viewing angle along the direction of the CSM, as in Figure \ref{['fig:allmodels_latetime']}, which represents the maximum absorption due to both FFA and SSA. The shaded region encompasses the range of emission between the face-on and edge-on viewing angles. The scatter points represent the same events as listed in the legend of Figure \ref{['fig:allmodels_latetime']}. Bottom row: Light curves of radio emission at 15 GHz for the same models as in the top row. The scatter points represent the same events as listed in the top right legend of Figure \ref{['fig:allmodels_earlytime']}.