Orbital Decay in a 20 Minute Orbital Period Detached Binary with a Hydrogen-poor Low-mass White Dwarf

Creators: Burdge, Kevin B.; Fuller, Jim; Phinney, E. Sterl; van Roestel, Jan; Claret, Antonio; Cukanovaite, Elena; Gentile Fusillo, Nicola Pietro; Coughlin, Michael W.; Kaplan, David L.; Kupfer, Thomas; Tremblay, Pier-Emmanuel; Dekany, Richard G.; Duev, Dmitry A.; Feeney, Michael; Riddle, Reed; Kulkarni, S. R.; Prince, Thomas A.

Abstract

We report the discovery of a detached double white dwarf binary with an orbital period of ≈20.6 minutes, PTF J053332.05+020911.6. The visible object in this binary, PTF J0533+0209B, is a ≈0.17 M⊙ mass white dwarf with a helium-dominated atmosphere containing traces of hydrogen. This object exhibits ellipsoidal variations due to tidal deformation, and is the visible component in a single-lined spectroscopic binary with a velocity semi-amplitude of K_B = 618.7 ± 6.9 km s⁻¹. We have detected significant orbital decay due to the emission of gravitational radiation, and we expect that the Laser Interferometer Space Antenna (LISA) will detect this system with a signal to noise of 8.4^(+4.2)_(-3.0) after four years of operation. Because this system already has a well-determined orbital period, radial velocity semi-amplitude, temperature, atmospheric composition, surface gravity, and orbital decay rate, a LISA signal will help fully constrain the properties of this system by providing a direct measurement of its inclination. Thus, this binary demonstrates the synergy between electromagnetic and gravitational radiation for constraining the physical properties of an astrophysical object.

Additional Information

© 2019 The American Astronomical Society. Received 2019 October 23; revised 2019 October 31; accepted 2019 November 4; published 2019 November 15. K.B.B. thanks the National Aeronautics and Space Administration and the Heising-Simons Foundation for supporting his research. J.F. acknowledges support from an Innovator grant from The Rose Hills Foundation and the Sloan Foundation through grant FG-2018-10515. Based on observations obtained with the Samuel Oschin Telescope at the Palomar Observatory as part of the PTF project, a scientific collaboration between the California Institute of Technology, Columbia University, Las Cumbres Observatory, the Lawrence Berkeley National Laboratory, the National Energy Research Scientific Computing Center, the University of Oxford, and the Weizmann Institute of Science. The KPED team thanks the National Science Foundation and the National Optical Astronomical Observatory for making the Kitt Peak 2.1 m telescope available. The KPED team thanks the National Science Foundation, the National Optical Astronomical Observatory and the Murty family for support in the building and operation of KPED. In addition, they thank the CHIMERA project for use of the Electron Multiplying CCD (EMCCD). Some of the data presented herein were obtained at the W.M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W.M. Keck Foundation. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain. The research leading to these results has received funding from the European Research Council under the European Unions Horizon 2020 research and innovation program n.677706 (WD3D). This research benefited from interactions at the ZTF Theory Network Meeting that were funded by the Gordon and Betty Moore Foundation through grant GBMF5076 and support from the National Science Foundation through PHY-1748958. Facilities: - PO:1.2m (PTF), Keck:I (LRIS) - , Pan-STARRS - , Hale (Chimera - , DBSP) - , KPNO/NOAO (KPED). -

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