Expected evolution of the binary system ATLAS J1138-5139

TL;DR

This paper models the future evolution of the ultra-compact white dwarf binary ATLAS J1138-5139, predicting it will become an AM CVn system, potentially trigger a double-detonation supernova, and serve as a gravitational wave source.

Contribution

It provides the first detailed evolutionary prediction of ATLAS J1138-5139 using MESA, including its potential to become a supernova and gravitational wave source.

Findings

Will evolve into an AM CVn system in ~6.3 Myr

He shell buildup may trigger a double-detonation supernova

Promising target for future gravitational wave detectors

Abstract

ATLAS J1138-5139 is a newly detected ultra-compact double white dwarf (DWD) system which is composed of a $1.02\,M_{\odot}$ carbon-oxygen white dwarf (CO WD) and a $0.24\,M_{\odot}$ helium (He) WD with an orbital period of about 27.68 min, making it one of the shortest-period DWD systems known. The future evolution and final fate of this system remain unexplored. In this work, we investigate the evolution of ATLAS J1138-5139 with the one-dimensional stellar evolution code Modules for Experiments in Stellar Astrophysics (MESA). We find that ATLAS J1138-5139 will evolve into an AM Canum Venaticorum (AM CVn) system in about \sim 6.3 Myr. Afterwards, the transferred material from the He WD companion start to build up to form a He shell near the surface of the CO WD. This accumulated He-shell masses can be up to approximately $0.12\,M_{\odot}$, which is likely to trigger a double-detonation (DDet) explosion of the CO WD. We therefore expect that ATLAS J1138-5139 will likely explode as a type Ia supernova eventually through the DDet explosion mechanism. Moreover, our calculations show that ATLAS J1138-5139 will be a promising target for gravitational-wave (GW) detection by future detectors like LISA, Tianqin and Taiji.