An eclipsing 8.56 minute orbital period mass-transferring binary

TL;DR

This paper reports the discovery and detailed analysis of a unique ultra-compact binary system with an 8.56-minute orbit, demonstrating its potential as a gravitational wave source and providing insights into mass transfer and orbital evolution.

Contribution

The study presents the first detailed characterization of an ultra-compact, mass-transferring binary with an 8.56-minute period, including orbital evolution and gravitational wave predictions.

Findings

Measured orbital period derivative Pdot = -1.60 ± 0.07 x 10^-12 s/s

Predicted strong gravitational wave signal detectable by LISA within four years

Identified the system as a helium-dominated accretion disk binary

Abstract

We report the discovery of ATLAS J101342.5-451656.8 (hereafter ATLAS J1013-4516), an 8.56 minute orbital period mass transferring AM Canum Venaticorum binary with mean Gaia magnitude G=19.51. The system was identified via periodic variability in Asteroid Terrestrial-impact Last Alert System light curves of Gaia white dwarf candidates. Follow-up spectroscopy with the Large Lenslet Array Magellan Spectrograph reveals a helium dominated accretion disk, while high speed ULTRACAM photometry shows pronounced primary and secondary eclipses. We construct a decade long orbital timing baseline using ATLAS and Gaia survey photometry together with high speed observations from ULTRACAM on the NTT and proto Lightspeed on the Magellan Clay telescope. From this baseline we measure an orbital period derivative Pdot = -1.60 +/- 0.07 x 10^-12 seconds per second. Interpreted in the context of stable mass transfer, the magnitude and sign of Pdot indicate orbital evolution governed by the interplay between gravitational wave driven angular momentum losses and mass transfer, directly probing the donor star structural response to mass loss. Assuming angular momentum loss dominated by gravitational radiation, we constrain the component masses and infer the characteristic gravitational wave strain. We predict a four year Laser Interferometer Space Antenna signal to noise ratio greater than 10, establishing ATLAS J1013-4516 as a strong prospective space based gravitational wave source that probes long term orbital evolution in the mass transferring regime.