Peculiar SN Ic 2022esa: An explosion of a massive Wolf-Rayet star in a binary as a precursor to a BH-BH binary?

TL;DR

This work identifies SN 2022esa as a genuine SN Ic-CSM exhibiting a coherent $P ~ 32$ days light-curve modulation, analyzed through multi-wavelength spectroscopy and time-series photometry. The period analysis, coupled with late-time O-rich CSI signatures, supports circumstellar interaction as the primary power source, though a post-SN binary engine remains a plausible alternative. The host environment indicates a young, massive WR progenitor in an eccentric binary, potentially leading to a BH-BH binary, with the data suggesting multiple channels contribute to the SN Ic-CSM population. Overall, the paper expands the SN Ic-CSM family, linking it to diverse massive binary evolution pathways and highlighting connections to Ibn/Icn events and double compact-object formation.

Abstract

A class of supernovae (SNe) termed `SN Ic-CSM' are characterized by late-time emergence of narrow emission lines of elements formed in the oxygen core of a massive star. A popular scenario is the interaction of the SN ejecta and O-rich circumstellar medium (CSM), i.e., Circumstellar Interaction (CSI). Uncovering the progenitor system of SNe Ic-CSM plays a critical role in understanding the final evolution of a massive star to a bare C+O star. In this Letter, we present observations of SN 2022esa which we show is an SN Ic-CSM. Surprisingly, a stable periodicity of ~32 days is found in its light-curve evolution with a hint of a slowly increasing period over ~200 days. We argue that the main power source is likely the interaction of the SN ejecta and O-rich CSM, while the energy input by the post-SN eccentric binary interaction within the SN ejecta is another possibility. In either case, we propose a massive Wolf-Rayet (WR) star as the progenitor, in a WR-WR or WR-BH (black hole) binary that will eventually evolve to a BH-BH binary. Specifically, in the CSI scenario, the progenitor system is an eccentric binary system with an orbital period of about a year, leading to the observed periodicity through the modulation in the CSM density structure. We also show that some other objects, superluminous SN I 2018ibb (a pair-instability SN candidate) and peculiar SN Ic 2022jli (the first example showing stable periodic modulation), show observational similarities to SNe Ic-CSM and may be categorized as SN Ic-CSM variants. Complemented with a large diversity in their light-curve evolution, we propose that SNe Ic-CSM (potentially linked to SNe Ibn/Icn) are a mixture of multiple channels that cover a range of properties in the progenitor star, the binary companion, and the binary orbit.

Figures (5)

• Figure 1: The spectral evolution of SN 2022esa, including the one (0.8 d) reported by lu2022. For the FOCAS spectrum on 448 d, the original ('SN+HII') spectrum is shown.
• Figure 2: The multi-band LCs of SN 2022esa around the peak (left) and those including the late-time measurements (right). The $g$- and $c$-band magnitudes are shifted by $+1$ mag for presentation. On the left panel, the mean LC (for ATLAS-o) is shown by a gray line. On the right panel, the WISE W1 (3.4$\micron$) and W2 (4.6 $\micron$) magnitudes (triangles) and $3\sigma$ upper limits (inversed triangles) are shown. Also shown are the full-deposition $^{56}$Ni/Co/Fe decay curve for $M$($^{56}$Ni)$=0.4$ and $0.05 M_\odot$, assuming that the explosion date is 15 days before the discovery. The epochs when the spectra were taken are indicated by short vertical lines on the $x$-axis.
• Figure 3: The fractional-residual LCs in the ATLAS-$o$ (orange), ZTF-$r$ (red), ZTF-$g$ (green), and the best fit sine curves through the LS analyses, are shown in the left panel. The data points that were rejected through the LS analyses are shown by crosses. In the middle panel, the power spectra, using the same color coordinates with those used in the left panel, are shown. In the right panel, the periods obtained through the sliding-window analysis (black) as well as using the full time window (red) are shown for the ZTF-$r$ data. The CSI-model predictions for the period change are shown by the dashed lines (see the main text).
• Figure 4: Comparison of the spectra of SN 2022esa to SNe Ic-CSM and related objects, in the early (top), peak/intermediate (middle), and late phases (bottom). In the bottom panel, the HII region-subtracted spectrum is shown. The data of the comparison objects are from the literature in section \ref{['sec:spec']}, and downloaded through WISeREP wiserep2012 or provided by the authors of the literature. The phases for the comparison objects are measured from the peak light (in their rest frames).
• Figure 5: The r-band LC of SN 2022esa as compared to SNe Icn and Ic-CSM (and related objects). The color coordinates are the same with figure \ref{['fig:spec_comp_Ic-CSM']} (note that SN Icn 2021ckj is replaced by SN Icn 2021csp; perley2022). Also shown here are SNe Ia-CSM 2020uem and IIn 2010jl.