SN2003bg: a broad-lined Type IIb Supernova with Hydrogen

TL;DR

This study models the spectra and light curve of Supernova 2003bg, revealing detailed ejecta composition, explosion energy, and progenitor mass, and highlighting its broad-lined features and hydrogen presence.

Contribution

It provides a comprehensive spectral and light curve analysis of SN 2003bg, offering new insights into its ejecta structure, composition, and explosion parameters compared to previous supernova models.

Findings

Ejected ~4 solar masses of material with ~5x10^51 erg energy.

Presence of a thin hydrogen layer (~0.05 M_sun) at high velocities.

Heavy elements, including ~0.2 M_sun of 56Ni, shape the light curve.

Abstract

Models for the spectra and the light curve, in the photospheric as well as in the late nebular phase, are used to infer the properties of the very radio-bright, broad-lined type IIb Supernova 2003bg. Consistent fits to the light curve and the spectral evolution are obtained with an explosion that ejected ~ 4 M_sun of material with a kinetic energy of ~ 5 10^51 erg. A thin layer of hydrogen, comprising ~ 0.05 M_sun, is inferred to be present in the ejecta at the highest velocities (v >~ 9000 km/s), while a thicker helium layer, comprising ~ 1.25 M_sun, was ejected at velocities between 6500 and 9000 km/s. At lower velocities, heavier elements are present, including ~ 0.2 M_sun of 56Ni that shape the light curve and the late-time nebular spectra. These values suggest that the progenitor star had a mass of ~ 20-25 M_sun (comparable to, but maybe somewhat smaller than that of the progenitor of the XRF/SN 2008D). The rather broad-lined early spectra are the result of the presence of a small amount of material (~ 0.03 M_sun) at velocities > 0.1 c, which carries ~ 10 % of the explosion kinetic energy. No clear signatures of a highly aspherical explosion are detected.