2020MNRAS.494L..91C

The Zwicky Transient Facility has begun to discover binary systems with orbital periods that are less than 1 h. Combined with dedicated follow-up systems, which allow for high-cadence photometry of these sources, systematic confirmation and characterization of these sources are now possible. Here, we report the discovery of ZTF J190125.42+530929.5, a 40.6-min orbital period, eclipsing double white dwarf binary. Both photometric modelling and spectroscopic modelling confirm its nature, yielding an estimated inclination of i = 86.2^+0.6_–0.2 deg and primary and secondary effective temperatures of \textrmT_\textrmeff = 28000⁺⁵⁰⁰_–500 and 17600⁺⁴⁰⁰_–400 K, respectively. This system adds to a growing list of sources for future gravitational-wave detectors and contributes to the demographic analysis of double degenerates.