A Single Degenerate Progenitor Model for Type Ia Supernovae Highly Exceeding the Chandrasekhar Mass Limit

TL;DR

This paper proposes a new single degenerate model for Type Ia supernovae where white dwarfs can exceed the Chandrasekhar limit up to 2.8 solar masses through accretion, rotation, and wind processes, explaining observed super-luminous supernovae.

Contribution

It introduces a novel SD progenitor model allowing white dwarf masses beyond the Chandrasekhar limit, incorporating differential rotation and wind effects to match high-luminosity SNe Ia observations.

Findings

White dwarfs can reach 2.3-2.7 M_sun in the model.

Different rotation states lead to varied explosion timings.

The model explains super-Chandrasekhar mass supernovae in low metallicity environments.

Abstract

Recent observations of Type Ia supernovae (SNe Ia) suggest that some of the progenitor white dwarfs (WDs) had masses up to 2.4-2.8 M_sun, highly exceeding the Chandrasekhar mass limit. We present a new single degenerate (SD) model for SN Ia progenitors, in which the WD mass possibly reaches 2.3-2.7 M_sun. Three binary evolution processes are incorporated; optically thick winds from mass-accreting WDs, mass-stripping from the binary companion star by the WD winds, and WDs being supported by differential rotation. The WD mass can increase by accretion up to 2.3 (2.7) M_sun from the initial value of 1.1 (1.2) M_sun, being consistent with high luminosity SNe Ia such as SN 2003fg, SN 2006gz, SN 2007if, and SN 2009dc. There are three characteristic mass ranges of exploding WDs. In an extreme massive case, differentially rotating WDs explode as an SN Ia soon after the WD mass exceeds 2.4 M_sun because of a secular instability at T/|W|\sim 0.14. For a mid mass range of M_WD=1.5-2.4 M_sun, it takes some time (spinning-down time) until carbon is ignited to induce an SN Ia explosion after the WD mass has reached maximum, because it needs a loss or redistribution of angular momentum. For a lower mass case of rigidly rotating WDs, M_WD=1.38-1.5 M_sun, the spinning-down time depends on the timescale of angular momentum loss from the WD. The difference in the spinning-down time may produce the "prompt" and "tardy" components. We also suggest the very bright super-Chandrasekhar mass SNe Ia are born in a low metallicity environment.