A gravitational wave detectable candidate Type Ia supernova progenitor

TL;DR

This paper reports the discovery of a compact binary white dwarf system, ATLAS J1138-5139, which is a promising candidate for a Type Ia supernova progenitor detectable by future gravitational wave observatories like LISA.

Contribution

The study presents the first detailed observation of a potential Type Ia supernova progenitor system that is detectable by gravitational waves, enabling direct calibration of binary evolution models.

Findings

ATLAS J1138-5139 is a 28-minute orbital period binary white dwarf system.

The system contains a 1 solar mass carbon-oxygen white dwarf accreting from a helium-core white dwarf.

It is expected to produce a Type Ia supernova within a few million years or evolve into an AM CVn system.

Abstract

Type Ia supernovae, critical for studying cosmic expansion, arise from thermonuclear explosions of white dwarfs, but their precise progenitor pathways remain unclear. Growing evidence supports the ``double-degenerate'' scenario, where two white dwarfs interact. The absence of other companion types capable of explaining the observed Ia rate, along with observations of hyper-velocity white dwarfs interpreted as surviving companions of such systems provide compelling evidence in favor of this scenario. Upcoming millihertz gravitational wave observatories like the Laser Interferometer Space Antenna (LISA) are expected to detect thousands of double-degenerate systems, though the most compact known candidate Ia progenitors produce only marginally detectable gravitational wave signals. Here, we report observations of ATLAS J1138-5139, a binary white dwarf system with an orbital period of 28 minutes. Our analysis reveals a 1 solar mass carbon-oxygen white dwarf accreting from a helium-core white dwarf. Given its mass, the accreting carbon-oxygen white dwarf is poised to trigger a typical-luminosity Type Ia supernova within a few million years, or to evolve into a stably mass-transferring AM CVn system. ATLAS J1138-5139 provides a rare opportunity to calibrate binary evolution models by directly comparing observed orbital parameters and mass transfer rates closer to merger than any previously identified candidate Type Ia progenitor. Its compact orbit ensures detectability by LISA, demonstrating the potential of millihertz gravitational wave observatories to reveal a population of Type Ia progenitors on a Galactic scale, paving the way for multi-messenger studies offering insights into the origins of these cosmologically significant explosions.