Discovery of the progenitor of the type Ia supernova 2007on

TL;DR

This paper reports the discovery of a pre-supernova X-ray source at the location of SN 2007on, providing evidence that supports the white dwarf accretion model for this type Ia supernova, despite the galaxy's older age.

Contribution

The study presents the first direct identification of a supernova progenitor in pre-explosion X-ray images, favoring the accretion model for this specific supernova.

Findings

X-ray source detected at supernova location in pre-explosion images

No optical counterpart found for the X-ray source

Supports the white dwarf accretion model for SN 2007on

Abstract

Type Ia supernovae are exploding stars that are used to measure the accelerated expansion of the Universe and are responsible for most of the iron ever produced. Although there is general agreement that the exploding star is a white dwarf in a binary system, the exact configuration and trigger of the explosion is unclear, which could hamper their use for precision cosmology. Two families of progenitor models have been proposed. In the first, a white dwarf accretes material from a companion until it exceeds the Chandrasekhar mass, collapses and explodes. Alternatively, two white dwarfs merge, again causing catastrophic collapse and an explosion. It has hitherto been impossible to determine if either model is correct. Here we report the discovery of an object in pre-supernova archival X-ray images at the position of the recent type Ia supernova (2007on) in the elliptical galaxy NGC 1404. Deep optical images (also archival) show no sign of this object. From this we conclude that the X-ray source is the progenitor of the supernova, which favours the accretion model for this supernova, although the host galaxy is older (6-9 Gyr) than the age at which the explosions are predicted in the accreting models.