SN 2005ap: A Most Brilliant Explosion

TL;DR

SN 2005ap is the most luminous supernova observed, with a rapid light curve and high photospheric velocity, challenging existing models of supernova brightness and evolution.

Contribution

This paper reports the discovery and detailed spectroscopic and photometric analysis of SN 2005ap, the most luminous supernova, highlighting its unique rapid evolution and spectral features.

Findings

Peak absolute magnitude of -22.7

Rapid 1-3 week rise to maximum brightness

Spectral features indicating high photospheric velocity (~20,000 km/s)

Abstract

We present unfiltered photometric observations with ROTSE-III and optical spectroscopic follow-up with the HET and Keck of the most luminous supernova yet identified, SN 2005ap. The spectra taken about 3 days before and 6 days after maximum light show narrow emission lines (likely originating in the dwarf host) and absorption lines at a redshift of z=0.2832, which puts the peak unfiltered magnitude at -22.7 +/- 0.1 absolute. Broad P-Cygni features corresponding to H-alpha, CIII, NIII, and OIII, are further detected with a photospheric velocity of ~20,000 km/s. Unlike other highly luminous supernovae such as 2006gy and 2006tf that show slow photometric evolution, the light curve of SN 2005ap indicates a 1-3 week rise to peak followed by a relatively rapid decay. The spectra also lack the distinct emission peaks from moderately broadened (FWHM ~ 2,000 km/s) Balmer lines seen in SN 2006gy and SN 2006tf. We briefly discuss the origin of the extraordinary luminosity from a strong interaction as may be expected from a pair instability eruption or a GRB-like engine encased in a H/He envelope.