SLSNe outshine ordinary core-collapse events by a factor of ten or more. Their progenitors lose massive shells of material in pre-explosion pulsations, and their light curves are pumped by exotic central engines — millisecond magnetars and circumstellar interaction.
Scroll into the progenitorThe progenitors of hydrogen-poor SLSNe are massive (≳ 30 M☉), low-metallicity, rapidly rotating stars. Many of them undergo pulsational pair-instability or violent late-stage instabilities that eject shells of stellar material in the years leading up to explosion.
Those shells become the circumstellar medium (CSM) that will later be shocked by the supernova ejecta — turning kinetic energy into radiation.
The star's iron core collapses. An ordinary supernova explosion is launched — but on its own, it cannot account for the extreme luminosity that follows. The energy source has to be something else.
If a millisecond magnetar forms at the center, or if the ejecta interacts with dense CSM, the picture changes dramatically.
A newly formed, rapidly spinning, highly magnetized neutron star (P ≈ 1–10 ms, B ≈ 1014 G) spins down via magnetic dipole radiation. Its rotational energy reservoir of ~ 1052 erg is dumped into the surrounding ejecta — orders of magnitude more than radioactive decay alone could provide.
The wind nebula inflates a bubble inside the ejecta, thermalizing and re-radiating as observed optical/UV light.
Peak absolute magnitudes brighter than M ≈ −21 — sometimes M ≈ −22 or beyond. SLSNe-I are blue at peak, with characteristic O II absorption features that distinguish them from other transients.
The shape of the rise and decline encodes the central engine: magnetar spin-down powering produces a smoother, slower decline; CSM interaction produces erratic light curves with bumps and re-brightenings.
As the ejecta becomes optically thin, the spectrum transitions to a nebular regime dominated by forbidden emission lines. The line widths and strengths probe the ejecta mass, composition, and central-engine luminosity — and sometimes show bumpy late-time photometric behavior that hints at CSM shells.
SLSNe are valuable cosmologically as well: their extreme brightness makes them potentially detectable at z ≳ 4 with current and upcoming facilities (Roman, JWST, Rubin).