Early Emission from Double Detonation Type Ia Supernovae

TL;DR

This paper investigates the early electromagnetic signals from double detonation Type Ia supernovae, predicting distinct shock breakout and cooling emissions that could be detected by current and future surveys.

Contribution

It introduces a detailed model of early emission features specific to double detonation supernovae, including shock breakout and cooling signatures, highlighting their detectability.

Findings

Initial shock breakout flash lasts ~5 seconds in soft X-rays.

Shock cooling emission persists for 12-24 hours in optical/UV.

Predicted luminosities are within detection range of current surveys.

Abstract

A popular model for Type Ia supernovae (SNe Ia) is the detonation of a CO white dwarf (WD) that is triggered by the prior detonation of a thin surface layer of helium, known as a double detonation (DD). We explore the unique early electromagnetic signatures that are expected from collision of the CO detonation with the He detonation. The three features are (1) a shock breakout flash, (2) a stage of planar shock breakout cooling, and finally (3) shock cooling emission from the thermal energy released by the collision. The planar phase is unique to the unusual density profile of the He-detonated layer in comparison to the steep profile at a stellar edge as is usually considered for shock breakout. The shock cooling emission can be modified by recombination, and we explore these effects. All together, we expect an initial flash dominated by the planar phase of $\sim6\times10^{43}\,{\rm erg\,s^{-1}}$, which lasts ~5 s in the soft X-rays. This is followed by ~12-24 hrs of shock cooling at a luminosity of $3-10\times10^{40}\,{\rm erg\,s^{-1}}$ in the optical/UV. We discuss prospects for detection of this early DD emission with current and upcoming surveys.