Type Ib Supernova 2008D associated with the Luminous X-ray Transient 080109: An Energetic Explosion of a Massive Helium Star

TL;DR

This paper models supernova 2008D, revealing it as an energetic explosion of a massive helium star with specific progenitor properties, bridging normal supernovae and hypernovae in energy scale.

Contribution

It provides a detailed theoretical model linking the observed light curve and spectra to the progenitor's characteristics and explosion parameters, highlighting its intermediate nature.

Findings

SN 2008D is more energetic than typical core-collapse supernovae.

Progenitor had a 6-8 Msun He core with minimal hydrogen envelope.

Remnant mass near neutron star-black hole boundary.

Abstract

We present a theoretical model for supernova (SN) 2008D associated with the luminous X-ray transient 080109. The bolometric light curve and optical spectra of the SN are modelled based on the progenitor models and the explosion models obtained from hydrodynamic/nucleosynthetic calculations. We find that SN 2008D is a more energetic explosion than normal core-collapse supernovae, with an ejecta mass of Mej = 5.3 +- 1.0 Msun and a kinetic energy of E = 6.0 +- 2.5 x 10^{51} erg. The progenitor star of the SN has a 6-8 Msun He core with essentially no H envelope (< 5 x 10^{-4} Msun) prior to the explosion. The main-sequence mass of the progenitor is estimated to be Mms =20-25 Msun, with additional systematic uncertainties due to convection, mass loss, rotation, and binary effects. These properties are intermediate between those of normal SNe and hypernovae associated with gamma-ray bursts. The mass of the central remnant is estimated as 1.6 - 1.8 Msun, which is near the boundary between neutron star and black hole formation.