A Physical Model for SN 2001ay, a normal, bright, extremely slowly declining Type Ia supernova

TL;DR

This paper models SN 2001ay, a peculiar Type Ia supernova with unique light curve features, using pulsating delayed detonation models from a Chandrasekhar mass white dwarf with a carbon-rich core, explaining its slow decline and high velocity.

Contribution

It introduces a detailed physical model for SN 2001ay, demonstrating how its peculiar light curve and spectral features can be explained within the pulsating delayed detonation framework.

Findings

SN 2001ay's slow decline is due to higher explosion energy and Ni56 distribution.

The supernova's features fit within the Delta-m15 relation physics.

A new class of SN 2001ay-like SNe Ia with an anti-Phillips relation is proposed.

Abstract

We present a study of the peculiar Type Ia supernova 2001ay (SN 2001ay). The defining features of its peculiarity are: high velocity, broad lines, and a fast rising light curve, combined with the slowest known rate of decline. It is one magnitude dimmer than would be predicted from its observed value of Delta-m15, and shows broad spectral features. We base our analysis on detailed calculations for the explosion, light curves, and spectra. We demonstrate that consistency is key for both validating the models and probing the underlying physics. We show that this SN can be understood within the physics underlying the Delta-m15 relation, and in the framework of pulsating delayed detonation models originating from a Chandrasekhar mass, white dwarf, but with a progenitor core composed of 80% carbon. We suggest a possible scenario for stellar evolution which leads to such a progenitor. We show that the unusual light curve decline can be understood with the same physics as has been used to understand the Delta-m15 relation for normal SNe Ia. The decline relation can be explained by a combination of the temperature dependence of the opacity and excess or deficit of the peak luminosity, alpha, measured relative to the instantaneous rate of radiative decay energy generation. What differentiates SN 2001ay from normal SNe Ia is a higher explosion energy which leads to a shift of the Ni56 distribution towards higher velocity and alpha < 1. This result is responsible for the fast rise and slow decline. We define a class of SN 2001ay-like SNe Ia, which will show an anti-Phillips relation.