A Luminous and Fast-Expanding Type Ib Supernova SN 2012au

TL;DR

SN 2012au is a luminous, fast-expanding Type Ib supernova with high helium velocity, significant nickel production, and properties akin to energetic Type Ic supernovae, expanding understanding of supernova diversity.

Contribution

This study provides detailed photometric and spectroscopic analysis of SN 2012au, revealing its unique luminosity, velocity, and energetic properties among Type Ib supernovae.

Findings

Peak absolute magnitude of -18.7 mag

Helium line velocity around 15,000 km/s

Estimated nickel mass of 0.30 solar masses

Abstract

We present a set of photometric and spectroscopic observations of a bright Type Ib supernova SN 2012au from -6d until ~+150d after maximum. The shape of its early R-band light curve is similar to that of an average Type Ib/c supernova. The peak absolute magnitude is M_R=-18.7+-0.2 mag, which suggests that this supernova belongs to a very luminous group among Type Ib supernovae. The line velocity of He I {\lambda}5876 is about 15,000 km/s around maximum, which is much faster than that in a typical Type Ib supernova. From the quasi-bolometric peak luminosity of (6.7+-1.3)x10^(42) erg/s, we estimate the \Ni mass produced during the explosion as ~0.30 Msun. We also give a rough constraint to the ejecta mass 5-7 Msun and the kinetic energy (7-18)x10^(51) erg. We find a weak correlation between the peak absolute magnitude and He I velocity among Type Ib SNe. The similarities to SN 1998bw in the density structure inferred from the light curve model as well as the large peak bolometric luminosity suggest that SN 2012au had properties similar to energetic Type Ic supernovae.