Discovery of the Extremely Energetic Supernova 2008fz

TL;DR

This paper reports the discovery and analysis of supernova 2008fz, one of the most luminous supernovae observed, characterized by its energetic output, spectral features, and faint host galaxy, suggesting a link to low-metallicity, high star formation environments.

Contribution

The paper presents the first detailed observations of supernova 2008fz, highlighting its extreme luminosity and spectral evolution, and discusses its implications for supernova progenitors in low-mass, low-metallicity galaxies.

Findings

SN 2008fz emitted possibly the most optical energy observed for a supernova.

The supernova's luminosity exceeds that of SN 2006gy, with a peak magnitude of M_V = -22.3.

The host galaxy remains undetected, indicating a faint or low-mass galaxy environment.

Abstract

We report on the discovery and initial observations of the energetic type IIn supernova (SN), 2008fz. The optical energy emitted by SN 2008fz (based on the light curve over a 88 day period), is possibly the most ever observed for a supernova (1.4 x 10^51 erg). The event was more luminous than the type IIn SN 2006gy, but exhibited same smooth, slowly evolving light curve. As is characteristic of type IIn SN, the early spectra of 2008fz initially exhibited narrow Balmer lines which were replaced by a broader component at later times. The spectra also show a blue continuum with no signs of Ca or Na absorption, suggesting that there is little extinction due to intragalatic dust in the host or circumstellar material. No host galaxy is identified in prior coadded images reaching R ~ 22. From the supernova's redshift, z=0.133, we place an upper limit on the host of M_R=-17. The presence of the SN within such a faint host follows the majority of recently discovered highly luminous SN. A possible reason for this occurrence is the very high star formation rate occurring in low-mass galaxies in combination with the low metallicity environment, which makes the production of very massive stars possible. We determine the peak absolute magnitude of the event to be M_V = -22.3 from the initial photometry and the redshift distance, placing it among the most luminous supernovae discovered.