The Discovery of Two LISA Sources within 0.5 kpc

Abstract

We report the discovery of the brightest detached binary white dwarfs with periods less than an hour, which provide two new gravitational wave verification binaries for the Laser Interferometer Space Antenna (LISA). The first one, SMSS J033816.16$-$813929.9 (hereafter J0338), is a 30.6 min orbital period, $g=17.2$ mag detached double white dwarf binary with a Gaia parallax measurement that places it at a distance of 533 pc. The observed radial velocity and photometric variability provide precise constraints on the system parameters. J0338 contains a $0.230\pm 0.015M_{\odot }$ white dwarf with a $0.38_{-0.03}^{+0.05}{M}_{\odot }$ companion at an inclination of $69\pm 9^{\circ }$. The second system, SDSS J063449.92+380352.2 (hereafter J0634), is a 26.5 min orbital period, $g=17.0$ mag detached double white dwarf binary at a distance of 435 pc. J0634 contains a $0.452_{-0.062}^{+0.070}{M}_{\odot }$ white dwarf with a $0.209_{-0.021}^{+0.034}{M}_{\odot }$ companion at an inclination of $37\pm 7^{\circ }$. The more massive white dwarf in J0634 is hotter than its companion, even though tidal dissipation is predicted to be relatively inefficient at such periods. This suggests that the more massive white dwarf formed last. J0338 and J0634 will be detected by LISA with a signal-to-noise ratio of 5 and 19, respectively, after four years. We identified these two systems based on their overluminosity and $u$-band photometry. Follow-up of $u$-band selected Gaia targets will likely yield additional LISA verification binaries.

ApJ Letters, in press

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Cited by in corpus (7)

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• The ELM Survey. IX. A Complete Sample of Low Mass White Dwarf Binaries in the SDSS Footprint
• A Systematic Search for Short-period Close White Dwarf Binary Candidates Based on Gaia EDR3 Catalog and Zwicky Transient Facility Data
• An Eclipsing 47 minute Double White Dwarf Binary at 400 pc
• The first phase of mass transfer in low-mass binaries: neither stable nor a common envelope
• Precise Parameters for Two LISA Sources
• Magnetic dynamos in white dwarfs -III: explaining the occurrence of strong magnetic fields in close double white dwarfs