Diversity of Type Ia Supernovae Imprinted in Chemical Abundances

TL;DR

This paper investigates the chemical signatures of a proposed new class of Type Ia supernovae, called slow SNe Ia, which influence stellar abundances differently in galaxies like the LMC and the Milky Way.

Contribution

It introduces a novel class of slow SNe Ia with distinct nucleosynthesis yields, explaining observed abundance patterns in different galaxies.

Findings

Low [Cr,Mn,Ni/Fe] ratios observed in some stars are explained by slow SNe Ia.

The impact of slow SNe Ia is significant in the LMC but negligible in the Milky Way.

Detailed nucleosynthesis models support the existence of slow SNe Ia from white dwarf mergers.

Abstract

A time delay of Type Ia supernova (SN Ia) explosions hinders the imprint of their nucleosynthesis on stellar abundances. However, some occasional cases give birth to stars that avoid enrichment of their chemical compositions by massive stars and thereby exhibit a SN Ia-like elemental feature including a very low [Mg/Fe] (~-1). We highlight the elemental feature of Fe-group elements for two low-Mg/Fe objects detected in nearby galaxies, and propose the presence of a class of SNe Ia that yield the low abundance ratios of [Cr,Mn,Ni/Fe]. Our novel models of chemical evolution reveal that our proposed class of SNe Ia (slow SNe Ia) is associated with ones exploding on a long timescale after their stellar birth, and gives a significant impact on the chemical enrichment in the Large Magellanic Cloud (LMC). In the Galaxy, on the other hand, this effect is unseen due to the overwhelming enrichment by the major class of SNe Ia that explode promptly (prompt SNe Ia) and eject a large amount of Fe-group elements. This nicely explains the different [Cr,Mn,Ni/Fe] features between the two galaxies as well as the puzzling feature seen in the LMC stars exhibiting very low Ca but normal Mg abundances. Furthermore, the corresponding channel of slow SN Ia is exemplified by performing detailed nucleosynthesis calculations in the scheme of SNe Ia resulting from a 0.8+0.6 solar mass white dwarf merger.