# Early UV emission from disk-originated matter (DOM) in type Ia supernovae in the double degenerate scenario

## TL;DR

This paper proposes that early UV excess in some Type Ia supernovae can be explained by ejecta colliding with circumstellar matter from the merger process in the double degenerate scenario, challenging the single-degenerate interpretation.

## Contribution

It introduces a model-based definition of early excess light and demonstrates that ejecta collision with disk-originated matter explains early UV emission in specific SNe Ia, supporting the double degenerate scenario.

## Key findings

- Early excess light can be explained by ejecta collision with circumstellar matter.
- The model fits the light curves of iPTF14atg and SN 2012cg.
- Early excess does not necessarily indicate a stellar companion.

## Abstract

We show that the blue and UV excess emission at the first few days of some type Ia supernovae (SNe Ia) can be accounted for in the double degenerate (DD) scenario by the collision of the SN ejecta with circumstellar matter that was blown by the accretion disk formed during the merger process of the two white dwarfs (WDs). We assume that in cases of excess early light the disk blows the circumstellar matter, that we term disk-originated matter (DOM), hours to days before explosion. To perform our analysis we first provide a model-based definition for early excess light, replacing the definition of excess light relative to a power-law fit to the rising luminosity. We then examine the light curves of the SNe Ia iPTF14atg and SN 2012cg, and find that the collision of the ejecta with a DOM in the frame of the DD scenario can account for their early excess emission. Thus, early excess light does not necessarily imply the presence of a stellar companion in the frame of the single-degenerate scenario. Our findings further increase the variety of phenomena that the DD scenario can account for, and emphasize the need to consider all different SN Ia scenarios when interpreting observations.