Orbital Decay in a 20 Minute Orbital Period Detached Binary with a Hydrogen-poor Low-mass White Dwarf
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}-3.0+4.2 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.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- November 2019
- DOI:
- 10.3847/2041-8213/ab53e5
- arXiv:
- arXiv:1910.11389
- Bibcode:
- 2019ApJ...886L..12B
- Keywords:
-
- White dwarf stars;
- Gravitational wave sources;
- Compact binary stars;
- Detached binary stars;
- Ellipsoidal variable stars;
- Spectroscopic binary stars;
- Relativistic binary stars;
- High energy astrophysics;
- 1799;
- 677;
- 283;
- 375;
- 455;
- 1557;
- 1386;
- 739;
- Astrophysics - Solar and Stellar Astrophysics;
- Astrophysics - High Energy Astrophysical Phenomena
- E-Print:
- 12 pages, 9 figures, 3 tables. Published online by the Astrophysical Journal Letters November 15, 2019