SUPERNOVAE FROM WD-WD DIRECT COLLISIONS

Image: Supernova remnant N 63A. Credit: NASA/ESA/HEIC and The Hubble Heritage Team (STScI/AURA)

Models for supernovae (SNe) related to thermonuclear explosions of white dwarfs (WDs) have been extensively studied over the last few decades, mostly focusing on single degenerate (accretion of material of a WD) and double degenerate (WD-WD merger) scenarios.

In recent years it was suggested that WD-WD direct collisions (probably extremely rare and occurring only in dense stellar clusters) provide an additional channel for such explosions.

In a recent paper (Papish & Perets 2016) the authors investigate such explosions with a numerical code, and explore the role of Helium-shells in affecting the thermonuclear explosions.

They find that collisions of WDs with a high-mass He-shell give rise to helium detonation before the CO bulk detonation, while the helium detonation does not happen in the presence of a low-mass He-shell.

The authors conclude that the various effects arising from the contribution of low/high mass He layers change the kinematics and the morphological structure of collision-induced SNe and may thereby provide unique observational signatures for such SNe, and play a role in the chemical enrichment of galaxies and the production of intermediate elements and positrons from their longer-term decay.

Papish & Perets 2016 (accepted in ApJL)- Supernovae from direct collisions of white dwarfs and the role of helium shell ignition (arXiv)

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