An Eclipsing 47 minute Double White Dwarf Binary at 400 pc

TL;DR

This paper reports the discovery of a nearby, eclipsing double white dwarf binary with a very short 47-minute orbital period, which is a promising gravitational wave source and will merge in about 41 million years.

Contribution

The paper presents the first detailed characterization of a 47-minute orbital period double white dwarf system discovered by TESS, including mass measurements and gravitational wave prospects.

Findings

Closest eclipsing double WD binary at 400 pc

Orbital decay measurable within 10 years

System will merge in approximately 41 million years

Abstract

We present the discovery of the eclipsing double white dwarf (WD) binary WDJ 022558.21-692025.38 that has an orbital period of 47.19 min. Following identification with the Transiting Exoplanet Survey Satellite, we obtained time-series ground based spectroscopy and high-speed multi-band ULTRACAM photometry which indicate a primary DA WD of mass 0.40 +- 0.04 Msol and a 0.28 +- 0.02 Msol mass secondary WD, which is likely of type DA as well. The system becomes the third-closest eclipsing double WD binary discovered with a distance of approximately 400 pc and will be a detectable source for upcoming gravitational wave detectors in the mHz frequency range. Its orbital decay will be measurable photometrically within 10 yrs to a precision of better than 1%. The fate of the binary is to merge in approximately 41 Myr, likely forming a single, more massive WD.