Helium Shell Detonations on Low Mass White Dwarfs as a Possible Explanation for SN 2005E

TL;DR

This paper investigates helium shell detonations on low-mass white dwarfs as a potential explanation for the peculiar properties of calcium-rich faint supernovae like SN 2005E, through one-dimensional simulations of such explosions.

Contribution

It provides new simulation results showing how helium detonations on small CO cores can produce supernovae with observed calcium-rich, faint, and fast properties, supporting this as a viable explosion mechanism.

Findings

Low-density helium detonations produce calcium and titanium-rich ejecta.

High-density CO cores tend to produce mainly nickel and unburnt helium.

Models do not reproduce bright, fast supernovae like SNe 1885A, 1939B, 2002bj.

Abstract

Recently several type Ib supernovae (SNe; with the prototypical SN 2005E) have been shown to have atypical properties. These SNe are faint (absolute peak magnitude of ~ -15) and fast SNe that show unique composition. They are inferred to have low ejecta mass (a few tenths of a solar mass) and to be highly enriched in calcium, but poor in silicon elements and nickel. These SNe were therefore suggested to belong to a new class of calcium-rich faint SNe explosions. Their properties were proposed to be the result of helium detonations that may occur on helium accreting white dwarfs. In this paper we theoretically study the scenario of helium detonations, and focus on the results of detonations in accreted helium layers on low mass carbon-oxygen (CO) cores. We present new results from one dimensional simulations of such explosions, including their light curves and spectra. We find that when the density of the helium layer is low enough the helium detonation produces large amounts of intermediate elements, such as calcium and titanium, together with a large amount of unburnt helium. Our results suggest that the properties of calcium-rich faint SNe could indeed be consistent with the helium-detonation scenario on small CO cores. Above a certain density (larger CO cores) the detonation leaves mainly 56Ni and unburnt helium, and the predicted spectrum will unlikely fit the unique features of this class of SNe. Finally, none of our studied models reproduces the bright, fast evolving light curves of another type of peculiar SNe suggested to originate in helium detonations (SNe 1885A, 1939B and 2002bj).