Unveiling the nature of SN 2022jli: The first double-peaked stripped-envelope supernova showing periodic undulations and dust emission at late times

TL;DR

SN 2022jli presents a rare double-peaked stripped-envelope SN Ic with subsequent 12.5-day periodic undulations. The first maximum is consistent with a standard $M_{ ext{ej}} \sim 1.5\,M_{\odot}$, $M_{\mathrm{Ni}} \sim 0.12\,M_{\odot}$ SN Ic powered by $^{56}$Ni decay, while the second peak requires additional energy input consistent with a magnetar of $P \sim 48$ ms and $B \sim 8 \times 10^{14}$ G, possibly with a delayed birth. The light-curve undulations and correlated hydrogen line shifts point to a binary interaction or accretion process, supplemented by magnetar spin-down as a central engine; CO overtone emission and a late-time infrared excess indicate dust formation or echo effects. The results support a broader view in which magnetars power SE SNe, producing bumps, undulations, and late-time dust emission, and highlight SN 2022jli as a valuable link between normal SE SNe Ic and magnetar-powered, interacting transients.

Abstract

We present optical and infrared observations from maximum light until around +800 days of supernova (SN) 2022jli, a peculiar stripped-envelope (SE) SN showing two maxima, each one with a peak luminosity of about $3 \times 10^{42}$ erg s$^{-1}$, separated by 50 days. The second maximum is followed by unprecedented periodic undulations with a period of $P \sim 12.5$ days. The spectra and the photometric evolution of the first maximum are consistent with the behaviour of a standard SE SN with an ejecta mass of $\sim 1.5$ $M_{\odot}$ and a radioactive $^{56}$Ni mass of $\sim 0.12$ $M_{\odot}$. The optical spectra after +400 days relative to the first maximum correspond to a standard SN Ic event, and at late times SN 2022jli exhibits a significant drop in the optical luminosity, implying that the physical phenomena that produced the secondary maximum have ceased to power the SN light curve. Among other potential scenarios, we discuss how the second maximum could be powered by a magnetar, while the light curve periodic undulations could be produced by accretion of material from a companion star onto the neutron star in a binary system. The near-infrared spectra shows clear first CO overtone emission from about +190 days after the first maximum, and it becomes undetected at +400 days. A significant near-infrared excess from hot dust emission is detected at +238 days, having been produced by either newly formed dust in the SN ejecta or a strong near-infrared dust echo. Depending on the assumptions of the dust composition, the estimated dust mass is $2-16 \times 10^{-4}$ $M_{\odot}$. The potential magnetar power of the second maximum can fit into a more general picture in which magnetars are the power source of SE super-luminous SNe, and could explain bumps, undulations, and late-time excess emission in SE SNe.

Figures (22)

• Figure 1: Field of SN 2022jli in the $i$ band observed with the LDSS-3 mounted at the Clay telescope at Las Campanas Observatory on May 22, 2022. The position of the SN is indicated in the figure. North is up and east is to the left.
• Figure 2: Optical and NIR light curves of SN 2022jli. Circles correspond to survey photometry or NIR photometry repeatedly obtained using the same instrument or photometric system. Pentagons correspond to photometry computed from LDSS-3 and EFOSC2 spectroscopic acquisition images, diamonds are from late time Goodman photometry and triangles represent synthetic photometry computed from colour-matched spectra. The $g$-band photometry from ASAS-SN is shown using dark-green open circles to avoid confusion with other $g$-band photometry. The legend on the right specifies the colour code and the offsets employed to plot the different bands. Dotted lines are used to compare (extrapolate) the brightness decline from an early epoch to late times in a few relevant bands.
• Figure 3: Optical spectral sequence of SN 2022jli. The phase relative to the time of maximum light is indicated on the right. The spectra during the first $+250$ days are shown in the top panel in logarithmic scale, the nebular phase spectra are presented in the bottom panel. The smoothed nebular spectra using the Savitzky–Golay filter are shown in black, the original spectra are shown in grey.
• Figure 4: NIR spectral sequence of SN 2022jli (in black) compared with SN 2013ge drout16 and SN 2011dh ergon15. The position of several lines are indicated with vertical lines and the phase relative to the maximum is indicated on the right. Five selected epochs are presented in this figure.
• Figure 5: Unfiltered photometry reported by Monard to the TNS obtained at the Kleinkaroo Observatory in South Africa (black points). The dotted black line corresponds to a second order polynomial fitted to the photometry. The polynomial fit was performed weighting by the photometric uncertainties and the shaded area corresponds to the $1 \sigma$ uncertainty computed from the covariance matrix of the polynomial fit. From this fit we obtained that the epoch of maximum brightness was on MJD$= 59709.6 \pm 1.2$ days at an unfiltered brightness of $14.29 \pm 0.02$ mag; however, we assume more conservative uncertainties for these parameters (see text).