SN 2009bb: a Peculiar Broad-Lined Type Ic Supernova

TL;DR

SN 2009bb is a peculiar energetic broad-lined Type Ic supernova with unique features such as helium detection, strong radio emission, and high metallicity, suggesting a possible hidden gamma-ray burst component.

Contribution

This study provides detailed photometric and spectroscopic analysis of SN 2009bb, revealing its energetic nature and peculiar properties, and discusses the implications for supernova explosion mechanisms and central engines.

Findings

SN 2009bb ejected about 4.1 solar masses of material.

It had a kinetic energy of approximately 1.8x10^52 erg.

The supernova showed signs of a central engine and possible hidden gamma-ray burst.

Abstract

Ultraviolet, optical, and near-infrared photometry and optical spectroscopy of the broad-lined Type Ic supernova (SN) 2009bb are presented, following the flux evolution from -10 to +285 days past B-band maximum. Thanks to the very early discovery, it is possible to place tight constraints on the SN explosion epoch. The expansion velocities measured from near maximum spectra are found to be only slightly smaller than those measured from spectra of the prototype broad-lined SN 1998bw associated with GRB 980425. Fitting an analytical model to the pseudo-bolometric light curve of SN 2009bb suggests that 4.1+-1.9 Msun of material was ejected with 0.22 +-0.06 Msun of it being 56Ni. The resulting kinetic energy is 1.8+-0.7x10^52 erg. This, together with an absolute peak magnitude of MB=-18.36+-0.44, places SN 2009bb on the energetic and luminous end of the broad-lined Type Ic (SN Ic) sequence. Detection of helium in the early time optical spectra accompanied with strong radio emission, and high metallicity of its environment makes SN 2009bb a peculiar object. Similar to the case for GRBs, we find that the bulk explosion parameters of SN 2009bb cannot account for the copious energy coupled to relativistic ejecta, and conclude that another energy reservoir (a central engine) is required to power the radio emission. Nevertheless, the analysis of the SN 2009bb nebular spectrum suggests that the failed GRB detection is not imputable to a large angle between the line-of-sight and the GRB beamed radiation. Therefore, if a GRB was produced during the SN 2009bb explosion, it was below the threshold of the current generation of gamma-ray instruments.