@article{21705,
  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 (AM CVn) binary with a mean Gaia magnitude of G = 19.51, identified via periodic variability in light curves from the Asteroid Terrestrial-impact Last Alert System (ATLAS) of Gaia white dwarf candidates. Follow-up with the Large Lenslet Array Magellan Spectrograph shows a helium-dominated accretion disk, and high-speed ULTRACAM photometry reveals pronounced primary and secondary eclipses. We construct a decade-long timing baseline leveraging light curves from the ATLAS and Gaia surveys, as well as the high-speed imagers ULTRACAM on the New Energy Telescope and proto-Lightspeed on the Magellan Clay telescope. From this timing baseline, we measure an orbital period derivative of P 1.60 0.07 10 = ± × 12 s s−1. Interpreted in the context of stable mass transfer, the magnitude and sign of P indicate that the orbital evolution is governed by the interplay between gravitationalwave-driven angular-momentum losses and mass transfer, directly probing the donor’s structural response to mass loss. We constrain the accretor and donor mass based on stable mass-transfer arguments assuming angularmomentum loss dominated by gravitational-wave emission, allowing us to infer the characteristic gravitational
wave strain of the binary for future space-based GW observatories such as the Laser Interferometer Space Antenna (LISA). We predict a characteristic strain corresponding to a 4 yr LISA signal-to-noise ratio ≳10, establishing ATLAS J1013−4516 as a strong prospective LISA source that will probe long-term orbital evolution in the mass-transferring regime.},
  author       = {Chickles, Emma T. and Chakraborty, Joheen and Burdge, Kevin B. and Dhillon, Vik S. and Draghis, Paul and El-Badry, Kareem and Green, Matthew J. and Householder, Aaron and Hughes, Sarah and Layden, Christopher and Littlefair, Stuart P. and Munday, James and Pelisoli, Ingrid and Redden, Maya S. and Tonry, John and van Roestel, Joannes C and Angile, Francesco Elio and Brown, Alex J. and Segura, Noel Castro and Dinsmore, Jack and Dyer, Martin and Furesz, Gabor and Gabutti, Michelle and Garbutt, James and García-Mejía, Juliana and Jarvis, Daniel and Kennedy, Mark R. and Kerry, Paul and Mccormac, James and Mo, Geoffrey and Osip, Dave and Parsons, Steven and Pike, Eleanor and Piotrowski, John J. and Romani, Roger W. and Sahman, David and Simcoe, Rob},
  issn         = {1538-4357},
  journal      = {The Astrophysical Journal},
  number       = {2},
  publisher    = {IOP Publishing},
  title        = {{An eclipsing 8.56 minutes orbital period mass-transferring binary}},
  doi          = {10.3847/1538-4357/ae4871},
  volume       = {1000},
  year         = {2026},
}