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We report the discovery of two detached double white dwarf (WD) binaries, SDSS J082239.546+304857.19 and SDSS J104336.275+055149.90, with orbital periods of 40 and 46 min, respectively. The 40 min system is eclipsing; it is composed of a 0.30 Msun and a 0.52 Msun WD. The 46 min system is a likely LISA verification binary. The short 20 Myr and ~34 Myr gravitational wave merger times of the two binaries imply that many more such systems have formed and merged over the age of the Milky Way. We update the estimated Milky Way He+CO WD binary merger rate and affirm our previously published result: He+CO WD binaries merge at a rate at least 40 times greater than the formation rate of stable mass-transfer AM~CVn binaries, and so the majority must have unstable mass-transfer. The implication is that spin-orbit coupling in He+CO WD mergers is weak, or perhaps nova-like outbursts drive He+CO WDs into merger as proposed by Shen.
We report the discovery of ZTF J2243+5242, an eclipsing double white dwarf binary with an orbital period of just $8.8$ minutes, the second known eclipsing binary with an orbital period less than ten minutes. The system likely consists of two low-mass
We report the discovery of a 1201 s orbital period binary, the third shortest-period detached binary known. SDSS J232230.20+050942.06 contains two He-core white dwarfs orbiting with a 27 deg inclination. Located 0.76 kpc from the Sun, the binary has
We present high-quality ULTRACAM photometry of the eclipsing detached double-white dwarf binary NLTT 11748. This system consists of a carbon/oxygen white dwarf and an extremely-low mass (< 0.2 Msun) helium-core white dwarf in a 5.6 hr orbit. To date
We present the discovery of the first T dwarf + white dwarf binary system LSPM 1459+0857AB, confirmed through common proper motion and spectroscopy. The white dwarf is a high proper motion object from the LSPM catalogue that we confirm spectroscopica
The magnetic white dwarf SDSS J121209.31+013627.7 exhibits a weak, narrow Halpha emission line whose radial velocity and strength are modulated on a period of ~90 minutes. Though indicative of irradiation on a nearby companion, no cool continuum comp