iPTF16abc and the population of Type Ia supernovae: Comparing the photospheric, transitional and nebular phases

TL;DR

This study analyzes early and nebular phase data of Type Ia supernovae, revealing diversity in ejecta masses and suggesting multiple progenitor channels, including Chandrasekhar and sub-Chandrasekhar mass models.

Contribution

It provides a comparative analysis of early and nebular phases of SNe Ia, highlighting diversity in ejecta masses and supporting multiple progenitor scenarios.

Findings

Ejecta mass diversity indicated by transparency timescales (25-41 days).

Weak correlation between ejecta mass and peak luminosity.

Sub-Chandrasekhar models explain the full range, while Chandrasekhar models fit the brightest SNe.

Abstract

Key information about the progenitor system and the explosion mechanism of Type Ia supernovae (SNe~Ia) can be obtained from early observations, within a few days from explosion. iPTF16abc was discovered as a young SN~Ia with excellent early time data. Here, we present photometry and spectroscopy of the SN in the nebular phase. A comparison of the early time data with a sample of SNe~Ia shows distinct features, differing from normal SNe~Ia at early phases but similar to normal SNe~Ia at a few weeks after maximum light (i.e. the transitional phase) and well into the nebular phase. The transparency timescales ($t_0$) for this sample of SNe~Ia range between $\sim$ 25 and 41 days indicating a diversity in the ejecta masses. $t_0$ also weakly correlates with the peak bolometric luminosity, consistent with the interpretation that SNe with higher ejecta masses would produce more $^{56}$Ni. Comparing the $t_0$ and the maximum luminosity, L$_{max}$\, distribution of a sample of SNe~Ia to predictions from a wide range of explosion models we find an indication that the sub-Chandrasekhar mass models span the range of observed values. However, the bright end of the distribution can be better explained by Chandrasekhar mass delayed detonation models, hinting at multiple progenitor channels to explain the observed bolometric properties of SNe~Ia. iPTF16abc appears to be consistent with the predictions from the M$_{ch}$ models.