# The Most Luminous Supernovae

## TL;DR

Superluminous supernovae (SLSNe) are extremely bright stellar explosions classified into hydrogen-rich and poor types, with unique light curves and spectra, arising from massive, low-metallicity progenitors, and have potential for cosmological studies.

## Contribution

This review synthesizes observational data and discusses models of SLSNe, highlighting their classification, spectral evolution, progenitors, host environments, and potential for cosmology.

## Key findings

- SLSNe are significantly more luminous than normal supernovae.
- SLSNe-I can be distinguished by a peak magnitude threshold of M_g<-19.8 mag.
- Host galaxies of SLSNe tend to be low-mass and metal-poor.

## Abstract

Over a decade ago, a group of supernova explosions with peak luminosities far exceeding (often by >100) those of normal events, has been identified. These superluminous supernovae (SLSNe) have been a focus of intensive study. I review the accumulated observations and discuss the implications for the physics of these extreme explosions. SLSNe can be classified into hydrogen poor (SLSNe-I) and hydrogen rich (SLSNe-II) events. Combining photometric and spectroscopic analysis of samples of nearby SLSNe-I and lower-luminosity events, a threshold of M_g<-19.8 mag at peak appears to separate SLSNe-I from the normal population. SLSN-I light curves can be quite complex, presenting both early bumps and late post-peak undulations. SLSNe-I spectroscopically evolve from an early hot photospheric phase with a blue continuum and weak absorption lines, through a cool photospheric phase resembling spectra of SNe Ic, and into the late nebular phase. SLSNe-II are not nearly as well studied, lacking information based on large sample studies. Proposed models for the SLSN power source are challenged to explain all the observations. SLSNe arise from massive progenitors, with some events associated with very massive stars (M>40 solar). Host galaxies of SLSNe in the nearby universe tend to have low mass and sub-solar metallicity. SLSNe are rare, with rates <100 times lower than ordinary SNe. SLSN cosmology and their use as beacons to study the high-redshift universe offer exciting future prospects.