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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 white dwarfs, and will merge in approximately 400,000 years to form either an isolated hot subdwarf or an R Coronae Borealis star. Like its $6.91, rm min$ counterpart, ZTF J1539+5027, ZTF J2243+5242 will be among the strongest gravitational wave sources detectable by the space-based gravitational-wave detector The Laser Space Interferometer Antenna (LISA) because its gravitational-wave frequency falls near the peak of LISAs sensitivity. Based on its estimated distance of $d=2120^{+131}_{-115},rm pc$, LISA should detect the source within its first few months of operation, and should achieve a signal-to-noise ratio of $87pm5$ after four years. We find component masses of $M_A= 0.349^{+0.093}_{-0.074},M_odot$ and $M_B=0.384^{+0.114}_{-0.074},M_odot$, radii of $R_A=0.0308^{+0.0026}_{-0.0025},R_odot$ and $R_B = 0.0291^{+0.0032}_{-0.0024},R_odot$, and effective temperatures of $T_A=22200^{+1800}_{-1600},rm K$ and $T_B=16200^{+1200}_{-1000},rm K$. We determined all of these properties, and the distance to this system, using only photometric measurements, demonstrating a feasible way to estimate parameters for the large population of optically faint ($r>21 , m_{rm AB}$) gravitational-wave sources which the Vera Rubin Observatory (VRO) and LISA should identify.
The Zwicky Transient Facility has begun to discover binary systems with orbital periods that are less than 1,hr. Combined with dedicated follow-up systems, which allow for high-cadence photometry of these sources, systematic confirmation and characte
General relativity predicts that short orbital period binaries emit significant gravitational radiation, and the upcoming Laser Interferometer Space Antenna (LISA) is expected to detect tens of thousands of such systems; however, few have been identi
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 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 an
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