Neutrino and electromagnetic signatures from Superluminous Supernovae: a case study for SN 2017egm

Abstract

Superluminous supernovae (SLSNe) are rare transients that are $\sim 10 - 100$ times more luminous than ordinary stellar explosions, reaching peak optical luminosities $\sim 10^{44} - 10^{45}$ erg s$^{-1}$. The energy source powering SLSNe remains uncertain. In this work, we explore the multi-wavelength and multi-messenger signatures of the scenario in which SLSNe are powered by a newly born millisecond magnetar. We model the dynamical evolution and emission from the coupled system comprised of the magnetar, wind, nebula, and supernova ejecta, consistently evaluating the pair multiplicity of the wind and nebula regions, and the bulk wind Lorentz factor governing the $e^+ - e^-$ injection spectra in the nebula. We compute the thermal and non-thermal electromagnetic signatures, neutrino signatures, and investigate their detection prospects. For SN 2017egm, the nearest observed SLSNe, our prediction for high-energy gamma rays matches the recent detection by Fermi LAT. For neutrinos, using SN 2017egm a canonical SLSNe, we find that in the era of the Vera C. Rubin Observatory, a stacking analysis with upcoming neutrino observatories can lead to $3σ$ detection significance of neutrino events from a population of SLSNe within a decade of operation.

Figures (11)

• Figure 1: Model predictions (solid lines) and observational data (filled circles) for SN 2017egm. The top panel shows the time evolution of the bolometric luminosity ($L_{\rm bol}$), the middle panel shows the evolution of the thermal temperature ($T_{\rm th}$), and the bottom panel shows the evolution of the light curve in $0.1 - 500$ GeV band. The time at which $L_{\rm bol}$ peaks is defined as $t_{\rm pk}$ while $t$ denotes the time elapsed since the onset of the supernova.
• Figure 2: Time evolution of various components of the energy along with spin down and characteristic nebula and ejecta diffusion timescales, for our fiducial magnetar model for SN2017egm.
• Figure 3: Predicted electromagnetic spectra from our fiducial magnetar-powered SLSNe model at $100$ Mpc corresponding to the radio, X-ray, MeV, and gamma-ray bands at different time snapshots. The sensitivity curves for the relevant detectors in the given EM bands are also shown. Note that $F_\nu$ denotes spectral flux density, $L_\nu$ is the spectral luminosity, and $\nu L_\nu$ is the differential luminosity. The radio spectra (top) shows flux density while the middle and bottom panels show flux.
• Figure 4: Light curves from a SLSNe at $100$ Mpc corresponding to the radio, optical, infrared, X-ray and gamma-ray bands. The characteristic spindown ($t_{\rm sd}$) and ejecta diffusion ($t_{\rm diff,0}^{\rm ej}$) timescales are also shown. The representative frequencies (for radio), wavelengths (for optical and infrared), and energies (for X-ray and $\gamma-$ rays) are motivated by relevant bands from observational telescopes shown in Figure \ref{['fig:emspectra']}. The apparent and absolute magnitudes are shown by $m_{AB}$ and $M_{AB}$ respectively.
• Figure 5: Left: Observed neutrino fluence (all-flavors) for a magnetar-powered SLSN at 100 Mpc for timescales post core-collapse ranging from a few hours to a year. The corresponding $pp$ component from the ejecta is shown in fainter shades. Right: The detection significance for various current, upcoming, and proposed neutrino telescopes given the observation time ($T_{\rm obs}$) as a result of stacking a population of observed SLSNe using Rubin LSST within redshift of $z_{\rm max} = 1$, where we assume Rubin LSST observes $1/3$ of all SLSNe. Note that the all-flavor day-averaged effective area including the appropriate field of view is used (see Appendix \ref{['appsec:nu_stack']} for details) for IceCube, RNO-G, IceCube-Gen2, IceCube-Gen2 Radio, GRAND, and BEACON.